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Winter Twigs
Signs of Four Seasons

From Hands-On Nature, by Jenepher Linbgelbach, Vermont Institute of Natural Science. Available from Whitman Distribution Center (603) 448-0317. Reprinted with permission.

When trees lose their leaves many people feel they also lose their identity, but a bare tree has its own stark beauty when its branching pattern and individual twigs become visible. Careful examination of its winter twigs reveals many distinguishing features about each kind of tree. The wide variety of shapes. colors, textures, and patterns are exciting to see and to learn about.

Twigs give a miniature account of the tree's past, present, and future. At the tip of the twig, or close to it, there should be a bud. Budsformed the previous summer, are miniature branchlets containing. next spring's leaves and flowers. These are protected by bud scales, the arrangement of which is characteristic for each tree species. Bud scales are really modified leaves serving to protect the delicate growing point within from drying out or from injury. Willows characteristically have only one bud scale which unzips and comes off like a hood in spring. Maples have several overlapping scales while oaks have many scales arranged in five rows.

Buds at the tip of the branch are called terminal buds. They mark the end of one season's growth and contain the embryonic stages of the next season's growth. Last year's bud scales are also evident. Look for a narrow band of fine markings around the twig; the distance between the new terminal bud and last year's bud scale rings show how much the twig grew in one year.

Oaks have a cluster of terminal buds. Aspens have a single terminal bud. Some trees, like staghorn sumac and elms, have pseudoterminal buds. These are actually the final lateral or side buds formed on the twigs during the growing season and are thus not centered at the end, but pointed slightly to one side.

Buds on the side of the twig are called lateral buds and may contain flowers or leaves. When two sizes of lateral buds occur on one twig. the larger usually contains flowers and the smaller leaves. The location of these buds in an opposite, alternate, or whorled pattern is useful in identifying specific trees. Opposite buds, for example, will open to become twigs, growing opposite each other. These patterns are reflected in the branching pattern of the entire tree. Only a few trees have opposite branching; an easy way to remember them is to think of the acronym MADCAP HORSE. The letters stand for different families: M -- maple: A -- ash; D -- dogwood; CAP -- Caprifoliaceae (the family of plants including honeysuckle, elderberries, and viburnums); and HORSE -- horse chestnut tree.

Before leaves are shed each autumn a corky layer develops across the leaf stem where it joins the twig. Called the abscission layer, it gradually cuts off the supply of water and food. When the leaf drops off only a scar is left behind on the twig. The shape of the leaf scar reflects the shape of the end of the leaf petiole or stem. In most trees it is an oval, a crescent, or a triangle, but in a few trees such as sycamore and staghorn sumac it is almost circular, enclosing a lateral bud. The veins that serve to conduct food and water between the leaf and the twig also leave scars (within the leaf scars). Referred to as bundle scars they vary in numbers and patterns specific to different types of trees. In examining twigs carefully, one can find very interesting leaf scars; the butternut scar resembles a monkey face, with the bundle scars forming the monkey's eyes and mouth.

Lenticels are the corky vents through which gases are exchanged between the tree tissues and the outside air. The size. color, and density of these marks vary: on white birches lenticels appear as dark horizontal lines, on cherry trees the horizontal lenticels are light colored and smaller than those of the birches. and on maple and alder twigs they are light colored dots. Color is another characteristic of different twigs. Some are red (dogwoods and striped maple), others are golden yellow (weeping willows), and others vary from soft greys and browns to deep purples and bronze greens.

Twigs have one distinguishing feature that can only be seen by cutting through the twig itself. The very center, called the pith, is soft, food storage tissue. It varies in color, shape, and structure. Years ago the large central pith used to be pushed out of the twigs of some trees, such as elderberry and staghorn sumac, to make spouts for sugaring or whistles.

Sometimes the odor of a bruised twig is a noseworthy feature. Spicebush, sassafras, and tulip tree twigs have an extremely spicy odor. Both black birch and yellow birch smell and taste like wintergreen. Cherry twigs have a Strong, bitter, almond-like odor and taste.

Winter trees may appear as lifeless skeletons against a sombre landscape, but careful examination of their twigs reveals the prophecy of spring and the history of seasons gone by.

Suggested References:

Core and Ammons. Woody Plants in Winter. Pacific     Grove, CA: Boxwood Press, 1973. Harlow, William M. Fruit Key and Twig Key to Trees     and Shrubs. New York; Dover, 1946. Rockcastle, Verne. Winter Twigs. Cornell Science     Leaflet, Vol. 58, No. 2. Ithaca. NY. Cornell Science     Leaflets. Cornell University 14853. 25¢/copy) Symonds, George W. D, The Tree Identification Book.     New York: William Morrow, 1958. Stokes, Donald W. A Guide to Nature in Winter.     Boston, MA: Little, Brown, 1976.

ACTIVITIES

Focus: The winter twigs of each kind of tree are unique, but some of the features common to all show evidence of seasons past, and promise for the coming spring.

Activities	Materials
Initial Question: How are twigs important to a tree?
TWIN TWIGS Objective: To become familiar with general differences in appearance among several kinds of twigs. Divide into groups of 5. One person from each group should select a "secret" twig from the duplicate pile, face away from the group and describe the twig. The rest of the group, with examples of the different twigs spread before them. chooses the correct twig from the description. Check to make sure the two twigs are twin twigs. Repeat to match other twigs.	matching sets of twigs 4 or 5 different kinds, 1 set for each group and an additional set for the duplicate pile
COMPLETE A TWIG Objective: To introduce the parts of a twig and their functions. Give each pair of children a twig to examine carefully. Two parallel lines representing a skeletal twig should be drawn on the blackboard and the leader should complete the twig from the children's directions, or the children could take turns filling in the details, based on their observations. Include terminal bud, lateral bud, leaf scar, bundle scar, bud scale rings, and lenticels. Children may draw their own complete twigs.	twigs twigs enough for each pair to have one blackboard and chalk or felt board and cut out twig parts
TWIG HUNT Objective: To match some common twigs to the correct species of trees. Divide into small groups. Each group should be given a set of twigs from the various kinds of trees found growing nearby. Have the children look carefully at each twig to see special features so they will know what to look for outdoors. Point out that those with opposite buds will have opposite twigs on the trees, alternate buds will have alternate twigs. Outdoors, find the trees to match the twigs, and if possible, collect a seed or a leaf from those trees. Note: In early spring children might tie a string to one twig and check it weekly to watch its buds open.	sets of twigs from trees found on school grounds