Trees & Shrubs – Discover-Nature

Oak Tree Habitat, pt.3

In the past couple of blogs, we learned that oak trees are a keystone species in their habitat, especially for the vast network of relationships between oaks and insects.

^{Ladybug on oak tree leaf by EMFA16, Getty Images}

^{Leaf litter and under-bark room for rent, by Wayne S. Grazio, Nov 2013}

^{Insect holes & homes on cork oak, Quercus suber, by Bloor4ik, Getty Images}

Oak trees and their surroundings provide shelter and food from leaves, wood, bark, sap, flowers, pollen, and acorns to thousands of species of insects and other invertebrates. Shelter is provided on the tree, inside cavities or other fissures, among the leaf litter, and around the root systems. As oaks age, there are more opportunities for shelter and food, including after branches or the whole tree dies and falls to decay on the forest floor.

^{Chickadee nest by Jack VandenHeuval, Getty Images}

^{Chickadee eating a caterpillar by Bettina Arrigoni, May 2018}

Over 900 caterpillar species have been identified in oak habitats, more than three times the number found in forests dominated by maple trees. Canopy leaves and branches provide shelter and nesting opportunities for dozens of bird species who find a ready source of food within the insect populations. Ninety percent of bird species feed insects, especially caterpillars, to their young. The Carolina Chickadee feeds four to six chicks for 16 days before they fledge. Mealtimes require 400 to 500 caterpillars each day.

^{Aphids and ants by oday222, Getty Images Pro}

^{Philodromus praedatus spiders live mainly in mature oak trees, by Nikk, May 2016}

^{Oak gall by Michael Boubin, Getty Images}

Several species of flies and wasps lay their eggs on oak trees, stimulating a growth hormone in the tree to grow a gall, an outgrowth of bark, around the eggs. When the larvae hatch, secretions from the gall feed the larvae, and the gall provides protection to the developing insects. The abundance of insects attracts other invertebrates from higher up on the food chain. Spiders frequently inhabit mature oak trees hunting and feeding on many of the insect species. Aphid colonies are often found on oak trees, but cause little damage to the tree. Aphids feed on the sap from the tree and secrete a sticky, sugary substance called honeydew, a favorite food for ants. The ants protect the aphid colonies, keeping them underground during inclement weather and herding them up the tree in summer to ensure the aphids are well fed to keep producing more honeydew.

^{Fall webworm, Hyphantria cunea, by Anita Gould, Sep 2015; Polyphemus moth caterpillar, Antheraea polyphemus, by Ed Uthman, Sec 2018; Speckled wood caterpillar, Pararge aegeria, by Dean Morley, May 2013; Linden looper caterpillar, Erannis tillaria, by sankax, Jun 2009}

Insects and oak trees have created an environment rich in food for many of its inhabitants. According to Doug Tallamy, a leading entomologist at the University of Delaware, “caterpillars transfer more energy from plants to other animals than any other type of creature.” The loss of habitat for insects puts considerable strain on all other environments, including ones supporting ourselves. Insects do most of the work of pollination, allowing plants to reproduce. They also provide for quick decomposition and the return of nutrients to the soil for growing new plants. Insects are a driving force of the world’s food webs and are necessary for a healthy environment.

There are over 400 species of oaks worldwide, with about one quarter found in North America. As we have briefly touched upon in this series of blogs, oak trees provide opportunities for healthy habitats for many other species. For information and further discussion on the relationships between caterpillars and oak trees, please see The Nature Of Oaks, by Doug Tallamy.

Oak Tree Habitat, pt.2

In the last blog, we discussed oak trees as a keystone species, substantially affecting the types and abundance of other species in their habitat. There are 400-500 species of oaks worldwide, supporting an extraordinary 2,300 wildlife species not including fungi, bacteria, and other microorganisms. Oak trees in all stages of life and death have numerous biotic relationships with wildlife.

^{Badger in tree cavity by Byrdyak, Getty Images||Golden millipede in Lagos by efeghali, Getty Images||Neanura springtail by Henrik_L, Getty Images||Pileated woodpecker in oak tree by mtruchon, Getty Images||Slug & rollie pollies by Sonya Kate Wilson, Getty Images||Wood Mouse in tree cavity by byjohn, Getty Images}

Fungi are often identified as attacking oak trees, but they can have very beneficial relationships. Fungi growing in the ground assist an oak tree in getting nitrogen, phosphorous, and other nutrients out of the soil, and in return get carbon and energy from the sugars in the tree’s sap. Oaks provide a place to live for over 700 species of lichens, plus uncounted liverworts and mosses. Lichens covering the oak’s surface help to keep them free of fungal infections and invasive insects. Liverworts and mosses help oaks to retain water and release it into the soil over a long period of time. As oak limbs fall and decay, water retention softens the wood providing food and habitat for decomposers.

Green moss on oak tree by tntemerson, Getty Images

Lichen & peat moss on oak by Sean Gardner, Getty Images

Fallen oak leaves are slow to decompose due to their tannin and lignin content, both preservative compounds. Leaf litter, composed of several layers of fallen leaves, becomes habitat for many millions of species including millipedes, springtails, woodlice, slugs, beetles, ants, and other organisms that feed on decaying plants. Through their activities, the creatures of the leaf litter help to return nutrients to the trees.

Oak forest leaf litter by Tina_C_Olsen, Getty Images

Acorns, with high amounts of fats, proteins, and carbohydrates, are one of the healthiest and most sought after foods in the woodland. White oaks, living between 200 and 300 years, will produce about 3 million acorns during their lifetime. Many bird species eat acorns, but oak trees enjoy a special relationship with blue jays, whose beaks are strong enough to pry an acorn open. In autumn, blue jays enjoy feeding on acorns, but also cache them for winter, burying several at a time under a few inches of soil in various locations up to a mile from the originating tree. Although blue jays cache large quantities of acorns, they can only remember and retrieve about 25% of them, allowing many new oak trees to grow and spread into new areas.

Blue jay with red oak acorn by mirceaux, Getty Images

Oak trees support 31 mammal species who consume acorns for food, use the tree for shelter, or use the surrounding habitat for hunting. Gray squirrels and red squirrels favor acorns in the autumn and throughout the winter from caches hidden in nearby locations. They remember far more cache locations than blue jays, but there are still uneaten acorns that will germinate in spring to start new trees. Acorns are also a favorite food for badger, deer, wild board, and wood mouse.

^{Gray squirrel eating acorn by viktor2013, Getty Images}

^{Red squirrel with acorn by Neil_Burton, Getty Images}

Oak trees offer shelter for many species. Squirrels often build their nests high up among the leaves that provide protection from weather and predators. Dead branches, especially those with cavities, may remain on the tree for many years, providing excellent roost sites for bats. Open limbs, leafed areas, and cavities all provide nest sites for a variety of birds. In addition, the many insects drawn to oak trees provide a ready source of food for all of these nesters. Humans have been acorn consumers for millennia. Raw acorns, high in tannin content, can be toxic in larger quantities; but, properly prepared, acorns are high in calories, vitamin C, starch, magnesium, calcium, phosphorous, and antioxidants. They have been a food staple in many cultures and can be found in the records of ancient Greeks, Iberians, Japanese, and English.

Oak trees have many direct and indirect relationships with insects, which we will explore in the next blog.

Oak Tree Habitat, pt.1

Oak trees, genus Quercus, have over 400 species worldwide, but almost one-third are threatened with extinction. They are a keystone species, playing a central role in supporting the entire habitat in which they live. They maintain the structure and stability within their ecosystem, substantially affecting the types and abundance of other species. Oaks make up only 2% of plant species, but they directly support more than 30% of all plants and animals.

^{A great oak in Nottingham Forest by Peter Shaw, Getty Images}

Oak trees live from a few decades to several centuries. The Great Oak, Quercus agrifola, a species of Coast Live oak in California, is estimated to be over 2,000 years old. Oaks clean the air by absorbing pollution and sequestering carbon. They provide shelter, food, shade, and help to reduce erosion. Humans get food from the acorns, dyes from the tannin, and wood for construction, ships, and barrels, plus cork for stoppers and oak chips for smoking meat, fish, and cheese.

^{Red oak with new leaves, Quercus rubra, by aleroy4, Getty Images}

^{Oak forest leaf litter in winter by Whiteway, Getty Images Signature}

In spring, tender new leaves containing fresh sap are consumed by a variety of insects. In fall, older leaves will fall to the ground, but are slow to decompose, building up many layers of leaves over time which provide shelter for small woodland ground dwellers and food for decomposers.

^{Branches of red oak with catkins, Quercus rubra,}
^{by anmbph, Getty Images}

^{Texas Red Oak female flowers, Quercus buckleyi by Doug Goldman, USDA-NRCS National Plants Data Team}

Oak trees have both male and female flowers. Male flowers grow in early spring in long clusters hanging from tree limbs. The pollen is a favorite food for a large variety of insects, especially bees. Pollen is released slowly, over several weeks, to be blown by the wind to the female flowers, which appear as tiny, red flowers near the tips of twigs and new shoots. Female flowers are eaten by insects and are a favorite of red and gray squirrels. Oak flowers are one of the earliest food sources for animals in spring, and must be abundant on every tree so that some are able to survive to produce acorns, the seeds of the oak tree.

^{Bur Oak acorns, Quercus macrocarpa; Northern Red Oak acorns, Quercus rubra; Live Oak acorns, Quercus virginiana by Steve Hurst, ARS Systematic Botany and Mycology Laboratory, USDA-NRCS PLANTS Database;}

In late summer, after pollination, the female flower will produce a large, green nut called an acorn, which will mature in autumn, turn brown, and fall from the tree. Acorns are a nutritious food source for many animals, being high in energy, carbohydrates, and fat. In the eastern U.S., many species are dependent on acorn production, and the amount of available acorns significantly influences population sizes. Some acorns will find suitable ground for sending out a root and starting a new tree, but most will be eaten. Masting, an over-abundance of acorns, occurs every few years. It is thought that masting creates a better chance for new oak trees to grow by overwhelming the animal populations’ need for food. As a secondary result, animal populations may expand immediately following a mast year, only to have higher than normal mortality when food resources return to normal for the following years.

^{Bur Oak bark, Quercus macrocarpa by Herman, D.E., ND State Soil Conservation Committee, USDA-NRCS PLANTS Database}

^{Dead oak log in Bialowieza Forest by Nirian, Getty Images Signature}

Oak roots grow close to the ground’s surface and extend well beyond the circumference of the tree’s crown. A complex network of fungi live on the roots and provide additional nutrients to the tree, keeping both species healthy. As the trees grow and age, roots and bark develop crevices and holes in their surfaces, or chunks may become loose, providing niches for plants and animals to shelter and grow. Exposed wood gradually dies and decays providing even more habitat and food for decomposers and the other wildlife that live on them.

In our next post, we will take a look at some of the many species that oak trees directly and indirectly support with shelter, food, and breeding opportunities.

The Woodlands at the Turning, an Illinois oak savannah, by Justin Kern, Nov 4, 2013

Ash Trees

In the past, ash trees were one of the more common street trees in many urban areas of the United States. However, with the introduction of the Emerald ash borer, Agrilus planipennis, a member of the beetle family native to Asia, our native ash populations have suffered severe losses.

^{Emerald ash borer, Agrilus planipennis, by Leah Bauer, USDA FS Northern Research Station, Bugwood.org}

^{Emerald ash borer larva by Oregon Department of Agriculture, Mar 2023}

^{Emerald ash borer damage by John Hritz, Aug 2006}

Ash trees have been a popular “street tree” species for many urban areas. It is estimated that by the late 20th century, 20% of all parkway trees in Chicago were ash species. Green ash, Fraxinus pennsylvanica, likes moist soils, but grows well in most conditions. White ash, Fraxinus americana, is very similar to green ash, but prefers well-drained sites. Both have furrowed bark appearing as tight rectangular blocks on young trees, but deepening into longer furrows and ridges resembling a diamond-shaped pattern in mature trees. Black ash, Fraxinus nigra, often found on wet sites, is covered with irregular, knobby bumps. All the barks are grayish-brown.

^{Green ash, Fraxinus pennsylvanica, flowers by DonArnold, Aug 2023}

^{Ash tree samara by Herve Breton, Getty Images}

In spring, ash trees grow small green or purple flowers with no petals. Most are wind pollinated, although several bee species collect the pollen and contribute to some seed development. Flowers appear on both male and female trees, but only female trees develop seeds. Seeds are called samaras, or “helicopter seeds,” due to the distinctive whirling pattern they exhibit as they fall off the tree in a lazy spiral to the ground. The seed is housed in a fully rounded shell at one end of the single wing of each samara.

^{Green ash, pinnately compound leaves by Robert H. Mohlenbrock. 1989, USDA NRCS Wetland Science Institute (WSI), Lincoln}

Its pinnately compound leaves are another distinctive feature of the ash family. A compound leaf has a leaf blade divided into leaflets that are attached individually to the middle vein, each by its own stalk. The term pinnately refers to the arrangement of leaves, opposite one another along the middle vein. A terminal leaf, grown at the tip of the vein means there are always an odd number of leaflets, from 5 to 9 leaflets in ash species. Buds and branches also grow in this pattern, which can be observed on rose plants, as well as hickory and walnut trees.

^{White ash trees in autumn color by Cathy McCray, Nov 2016}

White ash is the main source of wood used in commercial applications. It is of medium weight and springy, able to absorb a shock and bounce back. This makes it valuable for bats, tennis rackets, bows and arrow shafts, along with a wide variety of other uses including tool handles, boats, and furniture. The seeds provide a valuable food source for several bird species including quail, duck, and turkey.

^{Green ash, Fraxinus pennsylvanica, bark by Kerry Woods, Apr 2022}

^{White ash, Fraxinus americana, bark by Virens, Sep 2009}

^{Black ash, Fraxinus nigra , bark by Robert H. Mohlenbrock, 1995, USDA NRCS Wetland Science Institute (WSI), Chester}

Although many, many ash trees have been lost to attacks from Emerald ash borers over the past couple decades, a small number of green ash have proven more resistant. They provide great shade for parks, yards, and large areas. In fall, watch as white ash trees turn beautiful shades of gold, deep purple, and maroon. Be sure to make note of them on your walks and check back in a few months to view their spectacular fall displays.

Buttonbush

Over the past several days, there has been a lot of activity in our backyard pollinator garden in the area surrounding the buttonbush, Cephalanthus occidentalis. This native shrub is a multi-stemmed flowering species that can grow from 3′ to more than 12′ tall. It needs lots of sunshine and prefers moist soils. Found in many habitats including sub-tropical swamps, shrub swamps in the northeast and upper Midwest, and southern and northern floodplain forests east of the Mississippi, this species prefers swampy backwater areas, marshes, wet meadow and bogs.

^{Buttonbush, Cephalanthus occidentalis, whorled leaves by loonyhiker, Oct 2010}

Newer stems are green, but quickly turn dark brown to almost black, becoming scaly with age. Leaves are opposite or whorled around the stem, each one protruding at a slightly different angle than the one above. It is thought that this arrangement provides maximum exposure of the plant’s total leaf surface to the sun.

^{Buttonbush flowers by DonArnold, Jul 2023}

^{Bumblebee on buttonbush by DonArnold, Jul 2023}

The flower clusters appear as small balls between 1/2″ and 1″ in diameter, with over 200 spikes poking outward covering their entire surface. Each spike is actually an individual flower. Flowers are closely grouped together and exude an intense, sweet fragrance. The plant reproduces through a two-stage cycle where pollen is produced and falls onto the immature pistil. As visiting insects brush through the closely grouped flowers, pollen rubs off onto their bodies. Once the pollen is gone, the pistil matures and becomes sticky at the end. As other insects arrive, pollen from other plants is picked up by the sticky end to pollinate the plant.

After pollination is complete, and the flowers drop off the plant, the ball-shaped seedhead turns completely brown. Unless it is brushed off by a passing animal or it is eaten, the seedhead may remain with the plant through the entire winter season, dropping off in spring. Seeds will often disperse into wetland areas, floating to shore. Each seed ball contains two nutlets.

^{Red Admiral butterfly on buttonbush by DonArnold, Jul 2023; Honney bee on buttonbush by DonArnold, Jul 2023; Long-tongued tiger swallowtail on buttonbush by Owen Sholes, Getty Images}

Pollinators include many long-tongued insect species especially bumblebees, honey bees, tiger swallowtail butterflies and black swallowtail butterflies. In addition, over two dozen bird species utilize the shrub for food, shelter, and nest building material – most notably are wood ducks that use the plant’s structure to shelter their young. Amphibians and reptiles hide among clusters of buttonbush in wetland areas for protection during the breeding season. Several honey-producing bee species are attracted to its pollen and nectar.

^{Buttonbush, Cephalanthus occidentalis, by NC Wetlands, Aug 2018}

With more than a dozen buttonbush species worldwide, it is an easy plant find and get close to for observing its flowers and fruits, as well as the behaviors of the many animal species that frequent this shrub.

Summer Berries

Across the northern hemisphere, as spring moves into summer, animals are able to find more food sources. Amelanchier and mulberry trees are two fruit-bearing plants that are favorites of many bird and mammal species, including humans.

^{Amelanchier trees by Leonora Enking, Apr 2010}

^{Mulberry flower by Sueviews, May 2006}

^{Amelanchier grandiflora flower by Kurt Stuber, 2004}

Amelanchier is a genus of 30 species of pome-bearing fruit trees in the family Rosacea. This family includes several other fruit-bearing trees including apples, pears, and plums. The tree is a favorite for landscapers with its many white flowers covering the tree in early spring and its brilliant hues of red and orange in the autumn. Amelanchier can be a single stem or a multi-stemmed plant and will grow in almost any soil type, but the ideal habitat is partly sunny, well-drained areas of open woodland.

Amelanchier are known by many names. Serviceberry comes from the fact that when the plants are in bloom, the ground is thawed enough to hold funeral services. In the Cree Indian language, it is known as saskatoon, a name still commonly used in western North America. Shadblow, in old English, refers to a time when the bloom indicated the shad were running. Juneberry refers to the time of year when the berries ripen.

^{Amelanchier fruit by Oregon State University, Jul 2013; Immature mulberry fruit by Geo Lightspeed7, Apr 2022; Unripe white mulberries by Petru Dimitriu}

Serviceberry fruit is slightly larger than a blueberry and tastes of blueberry, lightly peppered with strawberry and almonds. The berries are light green when young and gradually grow plump and sweet as they ripen to dark red and purple. They are a favorite of many bird species including robins and cedar waxwings in my area. Fruit is rapidly eaten as soon as it starts to darken, and almost none is left to fully ripen unless the tree is covered with netting.

^{Cardinal eating mulberry by Carolyn Lehrke, Jun 2015}

^{Robin and mulberries by Zone~V, Jan 2016}

Mulberry trees, of the genus Morus, have 64 species worldwide, and are another important summer food source. Red mulberry, Morus rubra, is the only one native to the United States. White mulberry, Morus alba, is native to South Asia but can be found on many continents, and it is considered an invasive in parts of Brazil and the U.S. All species grow quickly when they are young, reaching heights of nearly 80 feet.

Mulberry trees can be easily grown from either seed or a plant cutting. The market for their fruit is worldwide with some places, such as the U.S., importing millions of pounds each year. While easy to grow, establishing a viable crop for market has many difficulties. Trees do not produce fruit for the first ten years, and their highest yields are when the trees are 30-80 years old. The fruit is a favorite of many bird and mammal species, and is often eaten well before it is ripe enough to pick. Leading producers are Turkey and Iran who have been growing mulberries for several centuries.

^{Pick your own mulberry by Katarina, May 2014}

^{Mulberry cobbler by Eden, Janine and Jim, Jun 2021}

^{Mulberry jam by Amanda Slater, Jul 2021}

Plump, juicy, and sweet berries from both plants are high in vitamin C and iron. Fruits can be eaten straight from the trees or used in a variety of recipes. Other parts of these plants contain a milky sap that is mildly toxic to animals and humans if ingested. The wood is hard, tight-grained and heavy, with many of the same qualities as oak. It is used in furniture and fence posts. Historically, it has been used for arrow shafts and body armor. Amelanchier leaves and bark may be dangerous to cattle, sheep, and goats if consumed in large quantities. The white mulberry, Morus alba, is an important tree for the silk industry. The leaves of this species are the only food source for the silkworm, Bombyx mori; its cocoons are used to produce silk.

^{Silkworm, Bombyx mori, on Morus alba by Gorkaazk}

As you walk woodland areas near your home, watch for berry-loaded trees in your neighborhood. Keep track of each time you see them and what stage the berries are in – and how many are left on the tree. See if you can observe and learn more about who is eating this sweet, juicy food source of summer.

Maple Trees

Maple trees in the northern U.S. are coming into bloom at this time of year. Maples bloom in late winter and early spring, and the flowers come in green, yellow, orange, and red hues. There are about 130 species worldwide, and except for one species, all are found in the northern hemisphere across Asia, Europe, Africa, and North America. Thirteen maple trees are native to North America, and we will take a look at a few of the more common ones.

^{Holland Red Maple Swamp, Wisconsin State Natural Area by Joshua Mayer, May 2012}

Several species are large trees, reaching from 40′ to 65′ in height with 20″ to 60″ diameter trunks. Trunks are dark grayish-brown with ridged bark. Crowns appear generally rounded and root systems are widely spread. Maple trees do well in most habitats, particularly moist to wet soil, along streams or in bottomlands.

^{Sugar maple in spring by J Stephen Conn, Jul 2007}

Sugar maple, Acer saccharum, is well known for its maple syrup, marketed world-wide. When temperatures drop below 40˚, maple trees stop growing and excess starch is stored until temperatures start to rise again. Enzymes in the tree change the starch into sugar which is carried by tree sap flowing through the xylem and phloem cells, located just beneath the bark. A tap gently pounded through the bark intercepts some of the sap and collects it into buckets. It takes 40 gallons of sap to produce one gallon of maple syrup. Historically, the wood was used for railroad rails, plow blades, and wagon wheels. After burning, its ashes are rich in potash and make excellent fertilizer as well as an additive for soap and pottery glazing.

^{Maple tree tapping by PublicDomainPictures , Pixabay}

Black maple, Acer nigrum, is a close relative to the sugar maple, and these two species easily hybridize. Both species are shade tolerant, often found growing together for several years as understory trees. Sap from black maple trees may also be used in maple syrup production. Black and sugar maples are hardwoods, stronger and harder than other maple species, and valued for use as basketball court and bowling alley floors, workbenches, cutting boards, and baseball bats.

^{Bowling alley by vtwinpixel, Getty Images; Maple & other baseball bats by Comstock Images: Maple workbenches from thelinke, Getty Images Signature}

Red maple, Acer rubrum, provides food from seeds, buds, and flowers for squirrels, chipmunks, deer, moose, and elk. In winter, stumps and small twigs are an important food source for rabbits. Pollen is produced early in the spring and is a much needed food source at this time of year for bees and other pollinators. Red maple is also attractive to insects and fungi, which invade the wood and create many open cavities in trunks and large branches, favored as nesting sites for wood ducks and other species.

^{Red maple buds & flowers by Martin LaBar, March 2010}

^{Baby squirrel in maple tree by William Krumpelman, Getty Images}

Red maple has several qualities that have made it a widely used ornamental tree. It grows well in shady sites; it is tolerant of flooding and water-logged soils; it is one of the first to colonize disturbed sites and anchor the soil, and it has a rapid growth rate, colorful flowers and foliage, and lives 75 to 100 years. Maple flavored drinks, such as tea, are made from inner bark scrapings. Bark is also used in the production of ink and black or brown dyes. The wood is used for smoking meat and in the production of some whisky varieties.

Silver maple, Acer saccharinum, is a fast growing tree with a root system attracted to any source of water. It is easily grown in shady areas and wet soils, make it a well-liked ornamental tree. However, it causes many sewer and drain issues in urban settings in its search for water. The wood is hard but very brittle, and branches easily break in heavy winds. This often results in trunks having hollow cavities used for shelter by various animal species including wood ducks and squirrels. Seeds are abundant and are a favorite for birds and small mammals. The sap makes a delicious syrup, but requires twice as much volume as sugar maple trees, making it not commercially viable.

Box elder, Acer negundo, is another maple species that is often found near water. This tree easily tolerates drought and extreme cold, although the wood is weak compared to other maple species, and branches often break when subjected to heavy loads of snow and ice. Box elder produces abundant seeds late in the year that provide a great winter food source for mice, squirrels, and seed-eating birds. Branches are small in diameter, so it is not often used for lumber, but it has several uses as pulp wood for producing crates, boxes, and composite wood panels.

^{Under the spreading maple by Jo Zimny, Oct 2020}

As you are out walking in your area, be sure to look for the many species of maple trees that grow in yards and woodlands, often distinguished by bright flowers, abundant seeds, and lively green foliage. Also, be sure to take the chance to observe their spectacular fall foliage later in the year.

Spring Wetland Vegetation

Early spring vegetation provides egg laying opportunities & protection

In early spring, when temperatures are still cool at night and daylight hours are just starting to lengthen, most plants are just starting to become active. Many amphibian and bird species also start their breeding activities at this time of year, and some of those depend on wetlands for egg laying sites, nesting material, food, and protection. Wetland vegetation creates important habitat for these species.

Emergent wetland at Kino Environmental Restoration project by Desert LCC, Aug 2018

Emergent plants are non-woody species that are rooted in wetland bottoms, but grow tall and emerge above the surface of the water. There are three categories of emergent plants that are important to pond life, including narrow-leaved emergents, broad-leaved emergents, and tall-robust emergents. Additional plants that affect wildlife populations in wetlands include floating plants, shrubs and trees.

Common bur reed, Sparganium eurycarpum, by USFWS Mountain-Prairie, Jul 2008

Common beggar’s ticks, Bidens frondosa, by Gertjan van Noord, Jul 2020

Marsh smartweed, Persicaria amphibia stipulacea, by Tom Wilberding, Aug 2020

Blue-joint grass, Calamagrostis canadensis, at Silver Lake, Utah, by Andrey Zharkikh, Aug 2014

Water willow, Justicia americana, by peganum, Jul 2017

Horsetail, Equisetum arvense, by delirium florens, May 2020

Narrow-leaved emergent plants are grasslike, with narrow stems and leaves, and grow to less than six feet in height. They come from the plant families that include sedges, Carex; rushes, Juncus; and bulrushes, Scripus. Some common narrow-leaved emergents of northern Illinois are common bur reed, Sparganium eurycarpum; horsetail, Equisetum arvense; reed canary grass, Phalaris arundinacea; and blue-joint grass, Calamagrostis canadensis. They provide cover for tadpoles and stems for perching birds to call from. Underwater stems are used to anchor frog egg sacs, and above surface leaves are used for egg laying by several species of dragonflies and damselflies.

Spot-tailed dasher, Micrathyria aequalis, on emergent vegetation by Allan Hopkins, Dec 2012

Eggs sacs anchored on emergent vegetation by JW112211, Apr 2006

Broad-leaved emergent plants are characterized by leaves almost as wide as they are long, and they grow to under three feet in height. Common species in northern Illinois include marsh smartweed, Persicaria amphibia stipulacea; common beggar’s ticks, Bidens frondosa; and water willow, Justicia americana. With broader leaves, these species provide excellent protection for adult and juvenile amphibians.

Cattail marsh at Jay Meiner Wetlands by Justin Meissen, Aug 2006

Tall-robust emergent plants are 5′ to 9′ tall when mature. Leaf and stem sizes vary greatly. In winter, some of the plants may die back or collapse, but many species grow in tightly packed stands where portions of the plant group will survive the entire winter. Examples in northern Illinois include narrow-leaved cattail, Typha angustifolia and broad-leaved cattail, Typha latifolia. In addition, common reed, Phragmites australis, is a highly invasive species found throughout our area.

Tadpole under duckweed by Helena, Jun 2007

Two other groups of plants are important to early spring wildlife. Shrubs, woody plants from 3′ to 9′ tall, and trees, woody plants over 9′ tall. Growing on wetland banks or in shallow water, trees and shrubs have branches and leaves that may be submerged or growing just above the surface. These provide perches for calling species, and some may be used for egg-laying sites. Common species in our area include blue-fruited dogwood, Cornus obliqua; silver maple, Acer saccharinum; and buttonbush, Cephelanthus occidentalis. Floating plants only grow on the surface where there is several inches of water. They are good indicators of water depth and the extent of open water in wetlands. They provide cover for many underwater eggs and juveniles. Duckweeds of the Lemna family and pond lilies in the Nuphar and Nymphaea families are common floating plants in this area.

Buttonbush, Cephelanthus occidentalis, by Jenny Evans, May 2008

Wetlands with emergent vegetation and stable water levels provide healthy habitat for bird, insect, and amphibian breeding populations. As you are out walking this spring, be sure to look at wetland vegetation and how it is used by the wildlife populations living there.

Tree Buds

Serviceberry, *Amelanchier arborea*, DonArnold Feb 2022

Trees produce buds for the next year’s leaves, flowers and shoots. They are small and not easily noticed among the foliage of a fully leafed-out tree, which is why they are easiest to spot in winter. Buds develop in late summer, when a tree has lots of energy from the sun, but is no longer growing new leaves and branches as the tree prepares for winter.

Bur Oak, *Quercus macrocarpa*, by DonArnold Feb 2022

American Linden, *Tilia americana*, by DonArnold Feb 2022

Tree buds remain dormant through the winter. In spring, as daylight lengthens and temperatures start to warm, buds will burst open. Buds contain the beginnings of a leaf, a shoot, or a flower. Terminal buds, located at the ends of branches, grow into new shoots. Lateral buds, growing along the sides of branches, produce either vegetative shoots or flowers.

*Ginkgo biloba* flower by Karren Wcisel 2004

Lateral buds that grow into flowers are well camouflaged and easy to miss. Frequently, flowers are dark red or green in color and are quite small, easily blending into the foliage. Many trees are wind pollinated, so there is no need for the flower to be showy. Once the flowers are pollinated, they quickly die; many only live for a few days.

Bur Oak shoot, 23 inches last year, by DonArnold Feb 2022

Terminal buds appear at the ends of branches and will create new shoots, allowing the branches to grow longer. These buds release a hormone named auxin that slows or prevents the growth of lateral buds on the same branch, so all of the energy for that extension of the tree goes into growing new wood. Arborists may prune terminal buds before they open to stimulate lateral bud development, thus controlling the shape of a tree.

Miyabe Maple, *Acer miyabei*, by DonArnold Feb 2022

Many buds are covered with scales. These are small, modified leaves that protect the bud in winter against cold, freeze damage, and drying. Buds contain stored energy in the form of sugars and nutrients to be used as soon as the buds burst in spring. This makes buds attractive as a winter food source for aphids, cedar waxwings, finches, squirrels and deer. Trees can lose some of their buds, but excessive predation could stunt tree growth.

Ginkgo bud & bark, *Ginkgo biloba*, by DonArnold Feb 2022

Red oak, *Quercus rubra* by DonArnold feb 2022

Freeman maple, *Acer fremanii*, by DonArnold Feb 2022

As you are out walking in the next few weeks, you will be able to see many trees with their buds getting ready to open. You may want to take along a field guide that describes characteristics of tree buds that can be used in winter tree identification. Two good ones are Winter Tree Finder by May Theilgaard Watts, and The Tree Identification Book by George W.D. Symonds. Both describe tree bud shape, color, size, and orientation, in addition to other tree parts.

Bark, pt.3

Bark provides protection for the tree from organisms trying to get under it to lay eggs and let larvae grow, to live out of the elements, or to feed. Whether bark is thick or thin, there are areas of good protection and areas of weak protection. Weak areas may include lenticels, cracks, branch junctions, wounds, broken branches, or open spots created by fire, frost, or other environmental actions. Many trees are weakened by drought and poor nutrition increasing the likelihood that the bark will not provide protection over the entire exterior surface.

Southern Live Oak tree by Thomas Cizauskas, July 2018

Broken branches after a storm by Indiana Public Media, January 2011

A mature tree can provide food and shelter for dozens of species, but not all visitors are harmless. Dutch Elm disease is caused by a fungal bacteria found on non-native beetles introduced to the U.S. through the landscaping trade in the early 1930s. Native elm trees had no defenses, and native elm beetles also picked up the fungus and spread it further.

Tunnels made by Emerald Ash Borer by Jessica_MCP, April 2010

Camponotus castaneus, Red carpenter ant, by Katja Schulz, October 2016

Pileated woodpecker by Dennis Church, January 2019

Insects that lay eggs under bark cause very little damage, but their larvae burrow through the cork layer, sometimes creating extensive tunnels that can damage the tree’s circulatory system. Where tunnels break through the surface, decay sets in. Carpenter ants feed on the decaying wood, opening the wounds further. Woodpeckers, especially the pileated woodpecker, feed on the carpenter ants, excavating wood to get to more ants. Tree sap, leaking from the damaged circulatory system, draws even more insects, and the cycle of damage continually worsens.

Beaver damage by Steve X. O’Neil, June 2009

Many animals feed on sap and inner bark in late fall and winter when food resources are scarce. This is also the time of year when the tree is least able to defend itself. Red squirrels and porcupines bite through bark on beech and maple to get to the sap. Beavers break through the outer bark of willow, aspen, poplar, and cottonwood to eat the inner bark. Native Americans and settlers harvested the inner bark of hemlock and pine to make flour. Deer, moose, and black bears strip bark to mark their territories.

Study of a tree trunk in rain by Denish C, October 2014

Many organisms use significant parts of a tree without harm. Peeling bark is used by birds for nest building. Smooth patch disease, easily observed on white oak, is caused by a fungus eating the exterior bark, but not penetrating to the inner bark. Insects move along bark cleaning up moss, lichen, and other material that may be clogging lenticels. Their presence attracts ants, spiders, and other predators. When it rains, water flowing down the bark carries minerals, nutrients, and organic matter from plants such as lichen and moss, plus fecal matter from bark dwelling insects, and washes it all into the root area providing additional resources to feed the tree.

Canker in tree trunk by Scot Nelson, October 2014

Tree trunk burl by Scot Nelson, October 2014

Trees have their own chemical and mechanical defenses to repel, isolate, and kill various organisms. Resin seals wounds to prevent desiccation and infection. The inner bark of black cherry contains hydrocyanic acid to repel bacteria, a chemical long used in cough drops. Tannin refers to a variety of compounds found in many plant species that is used to deter epiphytes, insects, and fungi. Trees may grow inner bark tissue to form a walled off area that isolates an organism that has breached the exterior bark. This area, covered by callous tissue sealing off the wound, is known as a canker, and results in a visible patch on the outer bark. Burls forms from abnormal wood growth around these areas.

Bark is an important and integral part of all trees, as well as a complex subject with much information still to be learned. There are several good resources available for further study, including Bark, A Field Guide to Trees of the Northeast by Michael Wojtech. As you are walking the woods this year, take some time to think about the role of bark not only in tree identification, but as a resource for the woodland habitat.

Bark pt.2

Ecology is the study of the relationship between organisms, each other and their environment. Bark is a highly visible part of a tree. By observing the color, thickness and function of the bark we can learn about the environmental factors that affect trees. These may include food production, fire, water availability, sunlight, wind, weather, and temperature.

Green layer under bark by Sheila Sund, August 2007

Food production occurs through photosynthesis in tree cells that contain chlorophyll. These cells are most often associated with green leaves, but many trees with smooth, thin, or peeling bark have these cells in the cork skin layer immediately below the outer bark layer. Sunlight can penetrate thin bark even on days where temperatures are below freezing. Warmth generated by sunlight on south or southwest sides of a tree will start photosynthesis. Trees growing in habitats with less than ideal growing conditions due to too much shade, a shorter growing season, or higher altitudes can depend on this secondary source of food production.

Rough bark of white oak, Quercus alba, by Doug Goldman, USDA NRCS Cape May PMC (NJPMC), United States, North Carolina, Guilford Co, Greensboro Oct 2011

Smooth bark of American beech, Fagus grandifolia, by Bruce Kirchoff, September 2010

Bark’s outer layer is made of dead cells filled with air. When combined with thickness, color, and density, these factors determine the effects of temperature fluctuations occurring from several sources. In winter, melting water from ice or snow can flow into any opening in the bark. When temperatures fall, rapidly drying and cooling bark refreezes the water causing it to expand and put pressure on the bark to create or enhance cracks or to pry the bark loose from the tree. Normally this promotes additional bark growth, but when repeated often over a short period of time, the tree’s appearance will become rougher with an increasingly uneven surface. Similarly, lightning changes the moisture content of bark into instant steam, splitting and blowing off sections of bark. Smooth bark species are much less affected as the energy follows the sheet of water down the smooth bark and into the ground.

Quaking aspen, Populus tremuloides, by Laura Bojanowski, October 2013

Sunlight is another factor both positively and negatively affecting a tree’s appearance. In winter, southward facing bark exposed to direct sunlight can heat to over 70 degrees. As the sun sets, dropping temperatures can cause bark to shrink around a still warm and expanded inner core resulting in stretching or cracking. This may also occur in trees subjected to hot sun and cool nighttime temperatures after bark has been dried out due to drought, reducing its ability to stretch. Some species with thin bark will reflect sunlight rather than absorbing it. Bark of the quaking aspen rubs off in powdery form that reflects sunlight well enough that Native Americans used the powder as sunscreen.

Paper birch, Betula papyrifera, by bambe1964, April 2010

Pitch pine, Pinus rigida, by StillRiverside, May 2015

Fire is a familiar environmental hazard. The best protection from fire comes from bark composed of several layers. Ridges, scales, plates, and furrows also contribute to keeping temperature fluctuation small on the inside of the tree. They have an uneven surface that retains moisture and makes them more resistant to the effects of fire. Trees growing in hotter, drier climates and more exposed to fire grow bark faster than other species. Pitch pine inhabits drier areas of the northeast U.S. and has bark that thickens at an early age and contains epicormic buds that sprout into new branches after exposure to fire. Some species have a different strategy for fire. Quaking aspen has thin bark that burns easily, but the trees resprout quickly and often from old rootstock. Paper birch also burns easily, but puts out a much greater quantity of seed annually than other species in the same habitat.

Hackberry, Celtis occidentalis, by Jimmy Smith, October 2009

American elm, Ulmus americana, by Matt Lavin, August 2010

Shagbark Hickory, Carya ovata, by Eli Sagot, March 2007

The environment places many stresses on the external layers of trees. Form, function, and appearance is initially determined by DNA, but is continually being modified by location and external forces. As you get outside or look out your window, try to identify the environmental factors affecting your trees. Next week, our final look at bark will deal with impacts from other organisms on trees.

Bark, pt.1

It has been cold outside for the last few weeks; and whenever we go outdoors, we tend to bundle up with warm coats, gloves, hats, boots, and long underwear. Animals and plants have their own strategies for living through the winter, including trees. Bark is an essential part of any tree. Bark provides protection, insulation, and plays a role in getting food to the rest of the tree. Bark can be used to identify tree species from the way it grows, its color, and its texture. However, bark can look different from tree to tree, and from branch to branch on the same tree.

There are several layers to a tree. The innermost layer is called wood and is made up of dead cells from previous year’s growth. Wrapped around the wood is the vascular cambium where new cells are growing inward to become the xylem layer that transports water and nutrients from the roots upward, and new cells growing outward to become the phloem that transports sugar and nutrients from the leaves to all parts of the tree. During winter, the need for food and water is much less as the tree enters a non-growing, dormant state, but circulation continues enough to keep the tree alive and hydrated.

Bark cross section drawing by Brer Lappin, Jan 2010

Bark consists of several layers starting with the phloem, also known as the inner bark. The periderm makes up the outer layers of bark protecting the phloem and other inner layers from environmental elements. The cork skin is the first layer of the periderm, containing cells to store food and waste products including tannins and resins. The cork cambium is the second layer where new cells are growing to add to the outside and final layer, the cork. Cork, mostly hollow, dead cells, prevents desiccation, provides insulation, and is a protective barrier from fungal and bacterial diseases.

Bark’s appearance is caused by both internal and external factors including growth, gas exchange, and the environment. At what rate are new cells being added to expand the tree? Does the bark stretch? Are there cracks or breaks in the bark? Bark thickness may vary from one-quarter inch on a mature beech to over an inch on a mature oak. Are there visible openings in the bark? Lenticels are specialized cells in the bark allowing an exchange of gases with the outside environment. Is temperature speeding or slowing growth? Has fire influenced the area? What affect has the wind had? Has the tree been attacked by bacteria, fungi, or animals? Have other plants used or damaged the tree?

Six bark appearance categories are commonly used to distinguish trees:

Smooth: Cork maintains a constant thickness throughout the life of the tree, and old cells slough off easily. An example is the American beech, Fagus grandifolia.
Horizontal peel: Expansion causes the external layer to peel away in strips when it is still quite thin. An example is river birch, Betula nigra.
Visible lenticel: Often a different color than the bark, lenticels can be oval, round, linear, or diamond-shaped. Some retain their shape over time, while others stretch as the tree grows. An example is pin oak, Quercus palustris.
Vertical cracks: Cracks often begin at lenticels, and they may be a different color depending on the color of the phloem layer that is exposed below. An example is pignut hickory, Carya glabra.
Scales, plates, or vertical strips: Each of these structures are separated on one or more sides from one another, and appear as overlapping sections of a similar size. Examples include black cherry, Prunus serotina, and American sycamore, Platanus occidentalis.
Ridges and furrows: As trees with hardened cork expand, the cork begins to crack. Sections are held together by fibrous tissue, creating furrows between ridges. Examples include Eastern cottonwood, Populus deltoides, and bur oak, Quercus macrocarpa

As you walk in the woods this season, consider taking along a tree guide to see how many trees you can identify by their bark. In a future installment on ecology, we will take a closer look at the role bark plays in the relationship between trees and their environments.

Smooth bark of *Fagus grandifolia*, American Beech by Derek Ramsey, Mar 2016

Horizontal peeling of *Betula nigra*, River Birch by Greg Hume, Feb 2016

Visible lenticels of *Quercus palustris*, Pin Oak by Dodshe, Aug 2011

Vertical cracks of *Carya glabra*, Pignut Hickory by Plant Image Library, Dec 2015

Plates of *Prunus serotina*, Black Cherry by Chhe, May 2009

Scales or vertical strips of *Platanus occidentalis*, American Sycamore by Rosser1954, Mar 2008

Ridges and furrows of *Populus deltoides*, Eastern Cottonwood by Cohee, Sep 2018

Ridges and furrows of *Quercus macrocarpa*, Bur Oak by Chhe, Jun 2009

Dead Trees

Trees offer a variety of services for wildlife, whether they are in a forest, a city park, or in your backyard. Trees grow slowly and die slowly. Each year, they flower, leaf out, and grow fruit throughout the spring and summer and then drop leaves and fruit each autumn. Often, one, two or more branches will die each year, even as new ones are being added. As each part of a tree dies, habitat is not lost; it is transformed into use for a variety of wildlife.

White oak snag by Frank D. Laspalluto, 2021

A hole in a tree can be created by a variety of events: branches broken off by weather or animals, trees being impaled by other trees during violent storms, or punctures or cuttings from human activities. Openings offer nesting sites for owls and flying squirrels. Bark at the lip of a hole will start to peel away allowing bats and spring peepers to get underneath for shelter. Small holes invite insects in, and woodpeckers searching for insect prey enlarge the holes. When a cavity becomes large enough to kill the entire tree, it is often used by tree swallows for nesting or as a great place for honeybees to build hives.

Red-shouldered hawk couple in the early morning light at the Venice Rookery, Venice, Florida, Lookout post by Diana Robinson, 2020

Snags are dead trees that remain standing. These offer birds of prey perches while they scan the areas underneath for small animals to hunt. After the snag becomes too weak to stand any longer and falls to the ground, it becomes shelter for numerous species. Mice and chipmunks use small holes to store food, raise young, and hibernate in for the winter. Large hollow logs offer a home for skunks and bobcats. Accumulated bark and leaf litter is a favorite place for toads and black rat snakes looking for a place to lay eggs. Shade provided under fallen logs promotes a damp environment, a favorite place for salamanders.

As wood starts to decay, decomposers move in. Fungi begins the process by breaking down the bark and returning the nutrients to the soil. Millipedes, termites, beetles, and ants all feed on rotting, decaying wood. Opossum, raccoon, robins and nuthatch find a treasure of insects and arthropods to feed on. Earthworms and grubs help to mix all of the droppings around the fallen log into the soil through their tunnel building activities, constantly enriching the soil.

Shelter for two by Lars-Goran Hedstrom, 2015

Dead trees are an important part of a forest ecosystem and can play a beneficial role in any habitat. Consider leaving branches where they drop, or artfully placing them into your own garden habitats. They provide shelter and food for many organisms, creating a rich and diverse community. Species that directly use the wood provide food for small organisms as they break down the wood and are prey themselves for larger animals. They release the nutrients trapped in the wood and enrich the soil in the process. They create shelter by opening new holes and enlarging existing ones for additional plants and animals to occupy. Next time you are out walking, gently turn over a log, and observe this wonderfully changing habitat.

Winter Tree ID, pt.2

Villages, public parks, and forest preserves in our area contain thousands of trees for our enjoyment. Being able to identify some or all of these can make our walks more fun. In the last blog, I identified several tree characteristics that can be used in tree identification in the winter. Here are some of the more common trees you may find in this area, along with their winter identification characteristics.

Silver Maple bark, by Jerry Jenkins, Forest Atlas Project

Silver Maple flower bud, by Jerry Jenkins, Forest Atlas Project

Silver Maple twig, by Jerry Jenkins, Forest Atlas Project

Silver maple, Acer saccharinum, is a native Illinois tree with bright yellow/green fall leaf colors. When looking at a twig, the terminal and lateral buds will all appear slightly reddish in hue and rounded or pointed. Remember that lateral buds are where new flowers or leaves will grow. If the buds are clustered, this is where flowers will bloom on the twig. The twig is slender and gray to red in color, with buds arranged opposite one another. If you scratch the twig with a fingernail and take a sniff, there is an unpleasant odor. The bark is smooth on young trees, becoming shaggy on older trees.

Hackberry bark, by Jerry Jenkins, Forest Atlas Project

Hackberry twig, by Jerry Jenkins, Forest Atlas Project

The hackberry, Celtis occidentalis, a favorite street tree, is a large, fast growing tree that can reach heights of 40 to 60 feet. Native to Illinois, the hackberry may live for 150 years or more. Twigs in winter lack a terminal bud, but have lateral buds that are brown, flat, and triangular in shape. Lateral buds display an alternate arrangement along very thin twigs. As each new twig grows at a slight angle from the bud, branches take on a zig-zag appearance. The bark, smooth and light gray, is covered with light colored lenticels, and is often times covered with wart-like bumps, their density being greatly variable. Cutting open a twig reveals a banded pith with visible cavities.

White Oak bark, by Jerry Jenkins, Forest Atlas Project

White Oak buds, by Jerry Jenkins, Forest Atlas Project

White oak, Quercus alba, is one of our most popular native hardwood trees. The state tree of Illinois, white oak is used for building dozens of items including cabinets, watertight barrels, floors, caskets, and pianos. In winter, look for bark that is light gray to silver in color. The bark can be quite variable from tight, shallow ridges to broad, loose flaky plating. Many trees exhibiting different bark formation on different parts of the trunk. Twigs display small, rounded, and reddish buds. Lateral buds are alternate on twigs that are slender, smooth and slightly reddish in appearance. Terminal buds are clustered with broad, hairless scales.

Black Walnut leaf scar, by Bruce Kitchoff,c-2015

Black Walnut pith, by Bruce Kitchoff,c-2015

Black walnut, Juglans nigra, is a slow growing tree with a large, shady canopy and rich, dark-brown hardwood. The wood will not warp, can be polished to a high luster, and is highly prized for furniture and veneers. The buds are gray with a light, fuzzy coating of hairs and arranged alternately along the twig. The leaf scars are heart-shaped and contain a very distinct bundle scar that looks like a “monkey face”. The pith is chambered, a distinctive trait found only in black walnut and butternut trees. The bark on this tree is dark brown, with high ridges and deep furrows often arrayed in a diamond-shaped pattern.

Bitternut Hickory bark, by Jerry Jenkins, Forest Atlas Project

Bitternut Hickory buds, by Jerry Jenkins, Forest Atlas Project

Bitternut hickory, Carya cordiformis, also a member of the walnut family, is a medium sized tree, growing 50′-80′ tall with a narrow canopy. This wood burns with an intense heat and is often used for smoking ham, bacon, and other meats due to the distinctive flavor imparted by the smoke. Twigs are thin, shiny, and greenish- to grayish-brown. The alternately arranged buds are bright yellow to sulfur-yellow, covered by two to four large scales that join one another along the edges without overlapping. The bark is light gray, appearing in a diamond-pattern with very shallow ridges.

These trees are some of the most commonly planted in urban communities and found in area forest preserves. All are native to Illinois, are hardy in urban settings, and provide food and shelter for many native wildlife species. Winter identification characteristics are easily visible and a great place to learn how to use a key. Take a walk and get started soon!

Winter Tree ID, pt.1

Many people can identify an oak tree or maple tree during the summer, but how can you ID a tree without leaves? There are several basic characteristics used in tree identification. Many of these are readily visible in winter. When looking at a tree, inspect several of the twigs, the smallest branches on a tree, to rule out any anomalies that may be present on only one. Different characteristics may appear on more than one tree, but when taken all together, a unique combination of traits will identify a single species. As you read the following, a drawing of a twig and all its relevant parts can be referenced at https://mekwamooks.wordpress.com/winter-id/.

The terminal bud, located at the tip of the twig, is where new growth will start from in the spring. Note its size relative to the twig, the bud’s shape, and whether or not it is covered with scales. Buds may be naked, not having any scales, or covered with overlapping scales, or scales may meet at their edges. Lateral buds are arranged along the length of the twig, and they are the site from which a new leaf or flower will grow next year. They will appear on the sides of the twig as you move along it. The arrangement may be opposite, when two buds are at the same point on either side of the twig, or alternate, when a bud on one side is spaced a few inches along the twig from the next bud on the other side.

Lenticels are specialized cells where gas exchange takes place during the growing season. They appear as light or dark spots along the twig. Note the color, size and amount found on a twig, or whether there are none. Running your fingers over the surface of the twig allows you to tell if the lenticels are smooth or rough and raised.

When leaves fall off the tree, they leave behind a leaf scar. Take note of the size and shape of a scar. Is it round, oval, heart-shaped or some other shape? Inside the leaf scar is the bundle scar, where the phloem and xylem layers that transport water and food entered each leaf. The arrangement of the bundle scar in addition to the size and shape of both scars is very helpful in determining the tree species.

The pith inside the twig is another part to use in identification. You will need to break off a twig and slice it lengthwise with a sharp pocketknife to see the center structure of the twig. It can be solid, hollow, spongy or chambered. This structure is found in young branches and is used to store and transport nutrients throughout the plant. As branches mature, storage and transportation will move to the xylem and phloem layers found just underneath the bark.

Peeling bark-Shagbark Hickory, by Jerry Jenkins, Forest Atlas Project

Smooth bark-Musclewood, by Jerry Jenkins, Forest Atlas Project

Warty bark-Hackberry, by Robert H. Mohlenbrock, hosted by the USDA-NRCS PLANTS Database

Bark, another highly visible feature, comes in a variety of colors from gray to tan to dark brown to black. Many species may have a hint of red tones. Identifying the texture of bark is very important. Is it smooth to your touch? Is it covered with warty patches? Some trees have bark that peels off, and it is important to note how the peel starts. Is it the top and bottom ends of each strip that are loose, or the middle that is pulling off to the right or left? Is the bark paper thin and coming off in loosely curled sheets? Thicker bark has a much rougher appearance. Does the bark run in ridges and furrows? Does it appear to be a diamond-shaped pattern on the tree? Some bark looks blocky, with no discernable pattern. Are the blocks flat to the tree or are there deep furrows between the blocks?

Blocky bark-White Oak, by Daniel O. Todd, hosted by the USDA-NRCS PLANTS Database

Furrowed bark-Bur Oak, by W.D. Brush, hosted by the USDA-NRCS PLANTS Database

As you accumulate clues, you can match them against identification guides. A special type of guide, known as a key, will help you identify many of the species found in a given geographic area covered by the key. Keys present a series of questions, each with a limited number of choices to select from. An example is “Winter Tree Finder” by May Theilgaard Watts and Tom Watts, “for identifying deciduous trees in winter.” This book uses a series of questions about twigs to lead the user to a correct identification.

There are many keys and field guides available, but remember to choose ones that pertain to the time of year you are in. Keys for flowers and leaves will not be of great value in winter, and many of the characteristics discussed above, such as scars and buds, will not be available to view in summer. I urge you to get out and try this fun activity before spring.

Publications to get you started:

Winter Tree Finder	May Theilgaard Watts & Tom Watts	Nature Study Guild, 1970
Trees of Illinois	Linda Kershaw	Lone Pine Publishing, 2007
Keys to the Trees of The Chicago Region	Ross C. Clark	The Morton Arboretum, 1988
Bark	Michael Wojtech	University Press of New England, 2011
The Tree Identification Book	George W.D. Symonds	Harper Collins, 1958
Twig Parts Explained	Volunteers @ Me-kwa-mooks Park, Seattle	https://mekwamooks.wordpress.com/winter-id/

Conifers

Conifers are one member of a group of plants known as gymnosperms, meaning ‘naked seeds’, a reference to the seed not being enclosed in an ovary or fruit. These plants do not flower, but have both male and female cones. The male cones carry pollen, which is dispersed by the wind. The female cones that come in contact with the blowing pollen will take some into the ova and produce seeds in the cone. Cones are green as they grow, turning brown as the seeds mature. When cones open, seeds are dispersed by falling to the ground or being picked up and moved by animals. In some conifer species, cones will not open until certain environmental conditions are met, namely the presence of fire. These species have serotinous cones, ones that only open when exposed to high heat. Fire also kills other plants that compete with conifers for resources such as sunlight and water, and it releases minerals from burned plants into the soil providing nutrients for new conifer seedlings.

White Spruce, *Picea glauca*, by Northern Forest Atlas Foundation

Most conifers are evergreen, although a few are deciduous. Deciduous trees lose their leaves all at the same time, when temperatures start to drop in autumn. Evergreens also lose their needles, a few at a time throughout the year, and they are quickly replaced by new growth so the tree is never bare. Evergreen needles are thin leaves found on several types of conifer including fir, spruce, and pine. Other types of conifers like juniper, cypress and cedar, have soft, scale-like needles. An examination of the needles is the best way to identify a conifer species. Whether they are stiff and sharp, or flexible and soft; bunched in groups or growing singly; and the number of needles that are in each bundle will help you to identify a specific tree species.

Austrian Pine, *Pinus nigra*, needles in sheathed pairs, by DonArnold

Climate conditions, especially temperature and precipitation, greatly influence the tree species found in any one area. Colder temperatures reduce the ability of plants to function. Deciduous plants handle this change by entering a state of dormancy until warmer temperatures arrive in spring. Precipitation in northern Illinois is generally well distributed throughout the year, although in winter, it falls as snow. Combined with a frozen soil layer, this water is not available for ready use by any plant species until the spring thaw. Evergreen species are well equipped to handle these conditions. Needles have a waxy, outer covering, while roots and stems are filled with resin, a chemical that acts as antifreeze. The general shape of the tree, with branches sloping down and out, keeps snow from accumulating and freezing on the foliage. The plants can survive very cold temperatures without damage and are able to start photosynthesizing food as soon as liquid water is available in spring. This gives evergreen species a jump on shorter growing seasons in cooler northern climates.

Austrian Pine, *Pinus nigra*, unopened seed cone, by DonArnold

Conifers in this area are used extensively by birds, mammals and insects for food and shelter. They make good habitat, providing protection from wind, rain and flying predators. A wide variety of insects call conifers home including spider mites, aphids, bark beetles and various caterpillars. Many of these insect species provide food for woodpeckers and nuthatches. Squirrel nests are well screened from wind and precipitation by evergreen boughs. During the day, many bird species like to browse among the ground litter of pine needles and fallen food. And later in the evening, that same activity is taken up by several mammals prowling the night time.

Hairy Woodpecker searching for insects on Austrian Pine, by DonArnold

There are about 700 conifer species found world-wide, and they can be found in backyards, city parks and nature areas all over DuPage County. They are most abundant in cooler climates and are important timber trees. All are softwoods, a versatile building material for mouldings, windows, flooring, paneling and plywood. They provide great backyard habitat in our area, and serve as an important natural resource for many over-wintering species in DuPage County.

Autumn Leaves

Autumn officially began just a few short weeks ago, but we are already able to observe the changing colors and leaf fall in the woods. There is much about nature that we can appreciate at this time of year, with observation and a little help from books, blogs and research.

Hackberry, *Celtis occidentalis* by DonArnold

Leaves on trees produce food for the rest of the tree. They do this by a process called photosynthesis which combines carbon dioxide, water, pigments and energy to create sugars and oxygen. The sugars are used to feed the rest of the tree. The oxygen is a by-product that is released into the surrounding atmosphere. The various pigments include chlorophylls, which allow a plant to absorb energy from light; carotenoids, which also assist in energy absorption; and xanthophylls, which protect the photosynthesis process from the toxic elements of light. All of these pigments give leaves certain colors. During spring and summer, chlorophylls are present in the highest concentrations, and they give leaves their green color. In autumn and winter, as the number of hours of light per day gets shorter, the photosynthesis process slows down and finally ceases. The amount of chlorophyll decreases and color from the other pigments starts to show through. Carotenoids are orange and yellow, while xanthophylls are yellow and brown. Another pigment that is only present when there is more sugar being produced than used by the plant is anthocyanin, and it colors the leaves red and purple.

Colors in autumn may be brilliant in some years, or more muted in other years. This intensity is determined by the weather conditions during late summer and autumn. Carotenoids and xanthophylls are always present in the leaves during food production season. Dry periods in late summer reduce the amount of sugar being produced. Thus, the red and purple hues from anthocyanin may be muted or not present at all, allowing more of the orange, yellow, and brown pigments to be displayed. Colors may be more muted with less moisture in the leaves and the length of time the leaves remain on the tree may be shortened.

White Ash, *Fraxinus americana*, by DonArnold

Color is also affected by temperature. When days are warm and sunny, leaves produce a lot of sugar. At night, in cooler weather, leaf veins constrict and limit the amount of sugar flowing to the rest of the plant, thus creating an excess of sugar remaining in the leaves each day. This is when we see lots of red and purple hues from anthocyanins displayed.

While leaves are falling, trees are preparing for spring in other ways. During senescence, that time of year when leaves grow old, carbohydrates, nitrogen, sulfur, phosphorous and potassium are reabsorbed by the tree in great quantities from the leaves. None of these elements are lost, but they are stored in twig, stem and root tissues. They will be used in springtime to fuel the beginning of the next year’s growth.

Another way for a tree to get a head start on next year comes from bud growth. Buds are formed in late summer or early fall, and are covered with modified leaves called bud scales. These will seal them against the cold and wet weather of winter. Most of the buds that you can observe are leaf buds containing tightly packed, immature leaves. In spring, when the weather gets warm enough for sap to start flowing, these buds will unfold into the first leaves of spring. Larger size buds may be flower buds, depending on the species and age of the tree. Flower buds do not change much in the winter months, but they will grow a bit larger as we get near bud burst in spring. You may also observe terminal buds, found at the ends of branches. Oak trees, as well as other species, add length to existing branches when these buds begin their spring growth.

There are numerous good field guides about trees available, but I would like to mention four that I use. “Winter Tree Finder” by May Thielgaard Watts and Tom Watts instructs you in how to look at a twig and its structures. Then the book guides you through an examination of a twig to identify the genus and species of deciduous trees in winter. “Trees of Illinois” by Linda Kershaw is another book organized using keys with excellent pictures of leaves, buds and fruit for each species, along with ranges and characteristics of each. “The Tree Identification Book” by George W.D. Symonds provides a wide variety of black and white photographs for every part of a tree including thorns, leaves, flowers, fruit, twigs, buds, bark and needles. Peterson Field Guides presents “Ecology of Eastern Forests,” with chapters describing the plants and animals encountered in different types of forests, and how they all function together. Other chapters talk about how forest patterns change with the various seasons.