Danielle Bell, FOCB Communications Chair
Most people look at a leaf to identify the species of tree or shrub they are admiring. But what about in winter? Our deciduous trees drop their leaves shortly after they senesce in the fall. When there are no leaves, we look to the small details of a twig to reveal the identity of woody plants. Winter buds are formed in late summer as the tree or shrub prepares to drop its leaves. These buds are “like tiny cocoons” as Barnes and Wagner describe them in their field guide, Michigan Trees. What a perfect analogy! You may be familiar with the transformation that moths and butterflies go through as they metaphorize from caterpillar larvae to adult butterfly or moth. But did you know that tree buds also transform from tiny protective shells to leaves, flowers, and twigs? All the future growth information a tree or shrub has is housed inside their tiny buds.
Nanny Berry bud scales opening, photo by Danielle Bell
The terminal bud is located at the tip of a branch and is the easiest to use to identify the tree species. It contains outer bud scales (if present), inner bud scales, embryonic leaves and the delicate embryonic growing point. The presence or absence of outer bud scales is the easiest characteristic of buds that aid in identification. Their color, size, number or arrangement is unique to each species. Nannyberry Viburnum has a pair of bud scales that are long and slender. Oaks have overlapping copper-colored armored scales. Bitternut Hickory and Witch Hazel, however, do not have outer bud scales at all. When no outer scales are present, they are called naked buds. Take your hand lens and you will see tiny leaves braving the long dark winter.
Elderberry flower bud, photo by Danielle Bell
Lateral buds are found along the stem above where the leaves were attached and are usually smaller than the terminal bud. These buds contain the coding for a new side branch with leaves or flowers. Some species have lateral buds specifically for flowers that are separate from the vegetative buds. Flower buds tend to be larger in size than lateral vegetative buds. Elderberry flower buds are some of the most impressive winter buds due to their large round size.
Leaf scars are another unique feature of twigs in winter. Located just below a lateral bud, they are the attachment sites of leaves during the last growing season. The size, shape and number of bundle scars are the three features that make leaf scars unique to a species. Bundle scars are where the vascular tissue connects the leaf to the roots. Black walnut leaf scars are one of my favorites!
It can be difficult to get outside in the winter with the limited daylight hours and chilly conditions but there are so many amazing wonders of nature to be discovered. Be sure to bring your hand lens on your next winter hike to fully appreciate the small details that reveal the secrets of woody plants. Or join Danielle Bell during our upcoming event Woody Plant Identification on January 25th at the Field Station and learn how to identify common woody species in winter.
