November 26, 2008
By Susan Benson,
CNHM Director of Education
When leaves fall off deciduous trees in the fall, it’s tempting to think that the tree is headed for a barren and lifeless winter season. But take a closer look — winter branches are not lifeless, but are in fact full of the promise of spring, even through the coldest stretches of winter. At the tip of each branch is a tiny bud, within which are future leaves, stems and flowers — folded, compressed, and covered by a waterproof coating of modified leaves called bud scales.
Through most of the year, tree buds enclose and protect the delicate growing tips of twigs and branches. During the winter, these buds act as protective cocoons, often sealed with wax and packed with moist cottony hairs to prevent the embryonic tissues from drying out.
Just as summer leaves vary in color and form, so do tree buds. In fact, in the absence of leaves, buds provide a good way to identify trees in autumn and winter. Their arrangement, size, shape, color, and the number, kind and arrangement of bud scales provide identification clues.
Buds provide for more than just the tree. Many animals rely on buds as an important food source during the winter, and particularly in the spring when the buds begin to swell. However, no great harm is done when a few buds are eaten; on a typical tree fully half the buds will not open in the season following their formation. If a squirrel nibbles away two or three future branches from a mature oak, for example, the nearest surviving bud will simply open to fill the void. Trees can also produce extra buds in areas of severe injury.
If you’re good at identifying trees by their leaves, try learning the differences among tree buds this winter. A good way to start is by finding a tree you can identify by some other means, say by the creamy white bark of the white birch, or a few characteristically lobed leaves still clinging to a red oak. Focus on the four common species first – oak, maple, ash, beech, birch, and aspen. Once you’ve learned these buds, move on to more challenging trees. On your next walk through the woods, get up close and look at buds for the unique traits they have.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its new facility in Cable at 13470 County Highway M or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Oak buds have many scales, overlapping in a spiral pattern like shingles on a roof. The buds are usually clustered near the tips of branches, where they are arranged in spiral patterns around the circumference of the twig.
Sugar maple buds have many scales arranged in staggered rows, the midpoint of one scale centered over the space between two lower scales. Sugar maple buds are brown and conical, resembling inverted ice cream cones but without the ice cream. \
Quaking aspens often feature a reddish-brown bud at the end of each twig, with smaller buds along the length of the twig. The buds can be slightly sticky to the touch, and have a glossy, varnished look.
White birch buds are tear-shaped, narrow and flattish, with one bud at the tip of each twig. The buds can be tacky or gummy to the touch.