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. 

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?

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/