September 2021 – Discover-Nature

Acorns

As I am out walking at this time of year, whether in the woods or around the neighborhood, there is lots of crunching underfoot. Acorns are one of the larger seeds littering the paths. There are about 450 species of oak trees worldwide and almost 90 in the United States with 17 native to Illinois.

An acorn is a fruit and a nut and a seed. Among Illinois species of oak trees, acorns grow between 5/16″ and 1-1/8″ in diameter, although many larger ones up to 3″ in diameter can be found in other parts of the world. One quarter of the seed is covered in a cupule, a saucer shaped cup that may or may not be fringed around the edges. The leathery shell, called a nut, is a hard, dry pod that surrounds a fruit with a single seed inside. Oak trees are in the genus Quercus in the beech family, Fagaceae, and are split into two sub-genera, white oaks and red oaks. White oak acorns grow to maturity each autumn when they fall off the trees. Red oak acorns are produced yearly, but have a two year growth cycle before maturing and falling off the tree.

Bur oak acorn, Quercus macrocarpa, by Steve Hurst, ARS Systematic Botany and Mycology Laboratory, Georgia

Mast is the accumulated fruit of trees and shrubs in forests, and acorns play an important part in oak-hickory dominated woods. They are large, easy to find and eat, and are rich in nutrients including protein, fats, and carbohydrates, plus the minerals calcium, phosphate and potassium and the vitamin niacin. White oak acorns are relatively sweet compared to the bitterness of red oak acorns. Both contain tannins, a compound that makes food taste bitter and may be toxic in large quantities. Animal species that eat red oak acorns typically cache them until water running over the cached nuts has leached out most of the tannin. Acorns in the Midwest are a favorite food for duck, turkey, quail, pheasant, squirrels, chipmunks, deer and bear.

White oak acorn, Quercus alba, by Steve Hurst, ARS Systematic Botany and Mycology Laboratory, Georgia

Acorns have never been used for human food on a scale reaching other nut varieties, but can be used for a variety of recipes. In times of famine, they were a staple for Greek and Japanese cultures. Korean noodles have been made from acorn flour since the early 1600s, while Ersatz coffee was made from large quantities of acorns during the Civil War. Acorns, which contain starch, can be ground into flour for bread, pastries and pasta. But all acorns require some leaching, involving soaking in several baths of clean water, to remove the tannins. Hot-water leaching or boiling acorns can accomplish this in three to four passes, but it also removes the starch necessary to hold the resulting flour together. Cold-water leaching takes a few days, but yields a better flour for baking.

Acorns are large and oak trees must rely on animals to move their seed around. Scatter-hoarding is a behavior used by jays and squirrels that gather acorns and cache them for later consumption. If the animal does not remember where all of its caches are, or it should perish before consuming all of the stored food, the remaining acorns have a chance to sprout and grow. Every six to seven years, often referred to as mast years, oak trees will produce many times more than the usual number of acorns. Current theory suggests that this is an attempt by the trees to overwhelm the consumers and increase the acorns chances of sprouting. Take your favorite tree field guide and get out to a forest near you to see what acorns you can find and identify the trees that are nearby.

Autumn Grass

In autumn, we think about the spectacular colors of the changing foliage. Ornamental grasses found in prairies, gardens and woodland edges are also showing shades of red, tan, and gold. They are part of the foundation of native plant species that cover prairies, savannas and meadows throughout the greater Midwest, and they are an important component in restoration projects and backyard gardens.

Indian grass, Sorghastrum nutans, by Brett Whaley, 2017

Grasses are classified as either cool-season grasses, which green up in early spring and go dormant by early autumn, or warm-season grasses which start actively growing after the soil is warm, typically from June 1st through late autumn in northern Illinois. Six of the most common warm-season grasses native to this area include prairie dropseed, Sporobolus heterolepis, Northern sea oats, Chasmanthium latifolium, little bluestem, Schizachyrium scoparium, switchgrass, Panicum virgatum, Indian grass, Sorghastrum nutans, and big bluestem, Andropogon gerardii.

Northern sea oats, Chasmanthium latifolium, by Robert H Mohlenbrock, 1989 @ USDA NRCS Wetland Science Insititue

Big bluestem, Andropogon gerardii, by Matt Lavin, 2015

Indian grass seedheads, Sorghastrum nutans, by Joshua Mayer, 2014

All of these grasses are native to Illinois and exhibit several common characteristics. Flowers are small, with stamens and stigmas exposed to the air. They have no nectar, but produce large amounts of smooth, light pollen that is easily carried away by any air movement. These grasses prefer full sun, but may grow in bright shade. They like moist conditions in well-drained soil, and are tolerant of rocky soil and drought. All of these species spread by dropping seed and a few also send out long, densely packed, underground root systems.

Switchgrass seed, Panicum virgatum, by Matt Lavin, 2015

Switchgrass, Panicum virgatum, by Matt Lavin, 2009

Grasses provide sustenance for many species finding their food sources dwindling at this time of year. Grasses can be cultivated or found growing wild in areas where it is available to cattle, bison, and horses. The foliage is also favored by a large number of insects including grasshoppers, leafhoppers, aphids, thrips, katydids and walking sticks. Several species of skipper caterpillars can be found among meadow and woodland edge grasses. Along with the great quantities of seeds being produced, the insects serve as a food source for grassland bird species.

Prairie dropseed, Sporobolus heterolepis, by Joshua Mayer, 2015

Prairie dropseed displays pink and purple flowers in late summer with a faint odor of buttered popcorn. It is a long-lived plant but hard to propagate, which is normally accomplished by subdividing each of its tufts. Northern sea oats is easily grown and has become a favorite of gardeners, although it can become an aggressive spreader. It is often used in flower arrangements for the large, flat seeds and leaves. Little bluestem is a common grass of rocky and thin soil areas. It is widely used in both restorations and gardens for its drought resistance and its spectacular blue and red palette. Big bluestem has earned the nickname of “turkeyfoot” due to the way the mature seed heads display at the end of tall flower stalks. Indian grass also grows tall and straight and maintains that posture throughout winter’s cold and wet weather. It is used as cover by Ring-necked Pheasants, Greater Prairie Chickens, Northern Bobwhites, and Field Sparrows. Switchgrass, another species that stays upright when wet, also provides winter cover for prairie deer mouse and house mouse. It has been evaluated as a source of alcohol for use as an alternative fuel. More alcohol per acre is generated by switchgrass than corn, and it is a perennial, but it is bulkier than corn making shipping and storage more costly.

*Little bluestem, Schizachyrium scoparium, by Patrick Alexander, 2011*

Native grasses are an integral part of the landscape of northern Illinois, providing food, shelter, and protection for many birds, insects, and mammals in autumn and through winter. With airy flower stalks, tall waving leaves, and striking colors of red, bronze, and gold, grasses add visual interest into every landscape.

Northern sea oats, Chasmanthium latifolium, by Scott Zona, 2021

Crickets

Nighttime brings out animals that are nocturnally active or that may simply be more noticeable during night hours. Rarely seen, but heard widely throughout the night, members of the cricket family, Gryllidae, may call at all hours of the day, or sing only during the night. Crickets are in the order Orthoptera, distinguished by having two pairs of wings, long, segmented antennae, chewing mouthparts, and the ability to sing by rubbing one body part against another.

Field cricket, Gryllus pennsylvanicus, by Mr.TinDC, Sandy Point, 2010

There are six groups of crickets found in Illinois encompassing many species. Field crickets are small, up to an inch long, black or dark red, and live in undergrowth that provides protection from wind and cold. Found across all of North America, adults and young cannot survive freezing temperatures and whole populations die off in the northern part of their range each year, while southern populations may produce multiple generations. Eggs are laid singly, in the soil in autumn, and a new generation hatches the following spring. A second group, house crickets, are not native to North America, and also cannot survive winter. Imported for many years as fishing bait and pet food, many escape to live and reproduce indoors. Females emit a chemical repellant to other females that encourage them to start new families elsewhere.

House cricket, Acheta domestica, by Gail Hampshire, 2010

Two additional groups, bush crickets and tree crickets, are common throughout the United States. Residing in trees, shrubs, and other vegetation, they are excellent singers. Females, locating a male to mate with by his song, nudge the male to interrupt his singing and they mate. The female punches a series of pin-like holes in thin bark, filling each with mucus and one egg, then plugs holes with chewed bark. The pattern of holes can be used to determine the species. Eggs overwinter under the bark, hatching in spring. Nymphs grow into adulthood by mid-summer. The last two groups include mole crickets that are strong flyers, but spend most of their lives underground, and camel crickets with short, wingless, hump-backed bodies.

Crickets, like grasshoppers, have a sharp edge called a scraper on one forewing that rubs against a bumpy ridge, called a file, on the underside of the other forewing. The song produced can be a chirp or a rapid trilling which is more musical than the grasshopper’s rasp and buzz. A cricket’s wings are long and tough. They are generally used for protection and flight, and are always used for singing. In addition to flight, crickets are jumping insects. They have three pairs of legs attached to the thorax. The first two are small, but the hind legs have enlarged, muscular thighs and rigid lower legs, with a knee joint designed to provide the ability to jump long distances.

Snowy tree cricket, Oecanthus fultoni, by Mark Yokoyama, 2015

Cricket songs are directly affected by temperature. As temperatures decrease, individuals will sing more slowly. For crickets, the pitch also decreases. Field crickets sing a series of chirps, and the outside temperature can be calculated from their song by applying Dolbear’s Law, named after A.E. Dolbear, who quantified the formula in 1897. Take the number of chirps per minute, subtract 40 and divide the result by four. Add fifty to get the temperature in degrees Fahrenheit, accurate to within one degree. Collecting crickets for their songs is a pastime in China and Japan where artisans have created beautifully decorated, hand-crafted cages for the past one thousand years. Tonight, after dark, take a stroll outside to hear the wonderful chorus in your neighborhood.

Silphiums

In the late summer, there are lots of bright colored flowers to see, and among the showiest of these are the four silphium species. Including compass plant, Silphium laciniatum, prairie dock, Silphium terebinthinaceum, cup plant, Silphium perfoliatum, and rosinweed, Silphium integrifolium, they stand tall with bright yellow daisy-like flowers that wave in the breeze. The name silphium comes from Greek meaning a resinous plant. The four plants we will look at today are found in a variety of habitats, and are all easily grown in our gardens.

Silphium perfoliatum, cup plant by Kerry Woods, 2007

Silphium perfoliatum, cup plant by Scott Zona, 2005

The cup plant likes sun and moist soil and can be found along stream and river edges, as well as in open woodlands and savannas. It is 4′-10′ tall, with a single, four-sided stem that only branches for the multiple flowers it supports. Leaves are opposite, about 4″x 8″ and join together on one side around the stem, forming a cup-like structure capable of holding water. Cup plants grow in large colonies providing an area for birds to rest out of the hot sun while searching for insects among the foliage and having drinking water readily available in the cups.

Silphium terebinthinaceum, prairie dock by Joshua Mayer, 2010

Silphium terebinthinaceum, prairie dock by Scott Zona, 2019

Prairie dock is found in wet or dry savannas. It has a vase-like cluster of leaves at the base of the plant with flowers on naked stalks from 3′-10′ high. A stout taproot extending nearly 12′ deep supports the plant. They prefer full sun and moist soil, but can tolerate drought well. Prairie dock often displays large, glossy black blotches on its foliage. These are formed by leaf beetles that lay their eggs on the leaf and cover them with a sticky substance that dries to a hard shell for protection. After the eggs hatch, the larvae will eat the leaf underneath while protected from above.

Silphium laciniatum, compass plant by Joshua Mayer

The compass plant, another species with a long taproot, grows 6′-12′ tall with leaves along the whole stem that gradually get smaller towards the top. A mature plant can live over 100 years, exhibiting up to 30 flowers in late summer for about six weeks. Young compass plants will align their leaves from north to south so they receive the cooler morning and evening sunlight. As early settlers crossed the prairie, they tended to use the alignment of the leaves for finding their way. However, older plants do not turn their leaves as readily, much to the woe of many wayfarers.

Silphium integrifolium, rosinweed by Frank Mayfield, 2006

Rosinweed has the shortest stature, standing 3′-5′ tall with a stout, central stem that branches at the base of the flowers. This is the only one of the four with a fragrant scent from the flower. Although it grows in sizable clumps, it is not an aggressive spreader from underground roots. Most clumps are composed of individual plants. The seeds are a favorite of goldfinch.

Silphium perfoliatum, Cup plant by Steve Hurst, ARS Systematic Botany and Mycology Laboratory, NJ, USDA-NRCS Plant Database

All of the silphiums are similar in appearance, with yellow flowers growing on tall stalks. They bloom in mid to late summer for four to six weeks. They are easy to maintain and resistant to drought, but may have a tendency to topple over when planted on slopes exposed to heavy wind. All are native to Illinois. Their foliage is rarely consumed by small mammals due to its coarse texture, but may be eaten by larger herbivores, including cattle. The disk florets, inner part of the flower, are sterile, while the ray florets, outer parts, are fertile. This is the exact opposite characteristic of that found in sunflowers.

Silphiums are a favorite of pollinator species including honeybees, bumblebees, miner bees, and ruby-throated hummingbirds. The flat, dark brown seeds are especially favored by goldfinch. Consider adding one or two of these plants to your garden for a bright background display.