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Woody Plants

More Buds

2-24-16 buds  019

The previous “bud scale” post engaged readers to an extent that made me feel another post with additional buds to scrutinize would be welcome. Apologies to non-woody plant aficionados!

When identifying woody plants in winter, one takes advantage of everything a tree or shrub has to tell you: bud/branch arrangement (opposite/alternate), bark, silhouette and terminal buds. Buds are so revealing that they alone can immediately tell you what species you are seeking to identify. Is there one bud at the tip of each branch (willows) or multiple terminal buds (red oak)? Are there bud scales (no-witch hazel; yes- bigtooth aspen)? If so, what are their number (willows – one) and arrangement (overlapping, like shingles – red oak)? Are the buds red (striped maple), brown (witch hazel), yellow (bitternut hickory), green, or some combination of these colors? Are they pointed (bigtooth aspen) or rounded (willow)? Every species of tree has buds with a unique combination of these characteristics.  Now is the time to observe them, as some will soon start to open.

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Bud Scales

bud scales 147Much of this coming summer’s woody plant growth is contained in embryonic form inside a tree’s buds. Buds contain an undeveloped shoot, leaf, and/or flower. Formed last summer, these buds must survive the freezing and fluctuating temperatures, relatively dry air and the potential insect, bird and fungal damage that may occur during the fall, winter and early spring.

Bud scales, which are small, modified leaves, cover and protect many of these buds. The number of scales, their arrangement, color, presence or absence of hairs or sticky substances are often distinctive. Willows have one visible bud scale (actually two fused into one), whereas pine and fir buds may have anywhere from 100 to 350. The scales on a bud can either be arranged in pairs facing each other edgewise (American Basswood, pictured) or overlapping like shingles (Sugar Maple, pictured). Colors range from the wine-colored bud scales of Striped Maple to the mustard yellow Bitternut Hickory scales. The texture of bud scales has great variation, including the satiny-smooth hairy bud scales of Box Elder (pictured). Many bud scales, such as poplars, are covered by a gummy substance which serves as added protection.

A few trees and shrubs have buds that lack scales. These are referred to as “naked” buds, and often the embryonic leaves are quite hairy. Witch Hazel, Hobblebush and Staghorn Sumac (pictured) are species of woody plants lacking bud scales.

Most buds have multiple scales which, upon falling off when the bud opens, leave a series of horizontally-elongated scars on the surface of the growing stem. By means of these scars one can determine the age of a young branch, since each year’s growth ends in the formation of a terminal bud which produces an additional group of bud scale scars. Continued growth of the branch causes these scars to be indistinguishable after a few years so that the age of older branches cannot be determined by this means.

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Southwest-facing Sides of Trees Have Most Stress in Winter

1-19-16 sun scald by Ginny P1000772A tree’s cells are normally dormant in the winter because of the cold temperatures, but the side of a tree trunk that faces the sun on a clear day can warm up enough that the cells become active. Even on a cold day, bark can warm to more than 50 degrees with direct sun on it. Once active, the cells are unable to return to dormancy by the time the sun goes down, which is when the temperature drops and can cause the active cells to die, resulting in what is referred to as sunscald. Dark bark can be a detriment to trees in winter, in that it absorbs rather than reflects the sun’s rays, thereby promoting the freeze-thaw-freeze cycle of cells.  This phenomenon occurs less frequently in forests, where the proximity of other trees offers some protection. (Photo by Virginia Barlow)
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Good Winter For Meadow Voles – Not So Much For Woody Plants

4-16-15  meadow vole sign 009Warming temperatures have revealed the considerable amount of activity that occurred under the protective deep layer of snow this past winter. In addition to a multitude of exposed meadow vole runways, there are ample signs of the voracious appetite of this small rodent. Given that more than 90% of a meadow vole’s diet consists of vegetable matter, that it can eat more than its own body weight in 24 hours, and that it breeds throughout the year, it is no surprise that the bark of many woody plants was consumed this winter, resulting in much girdling, and thus the demise, of many shrubs and saplings.

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White Ash Winter I.D.

2-19 white ash leaf scar 007White ash, Fraxinus americana, is relatively easy to identify in winter, between its stout, opposite branches and buds and the corky ridges that form diamond shapes on its bark. There are several species of ashes, however, and one feature that distinguishes White Ash is the shape of its leaf scars (located beneath leaf buds) on well-developed branches. Each leaf scar (left by a leaf that fell off the tree) is round at the bottom and notched at the top, resembling the letter “C” on its side. (No other ash has c-shaped leaf scars.) It is often concave along the upper edge and the lateral buds are located within the curved portion of the leaf scar.

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Speckled Alder in Winter

2-3-15 speckled alder 166Speckled Alder is a shrub in the Birch family that is found growing in wetlands. It is named after the “speckles” on its bark — horizontal lines or lenticels (spongy openings for the transfer of gases). In winter, Speckled Alder branches are distinctive because they carry two kinds of buds as well as last year’s fruit. The male flower buds are in the form of inch-long catkins which appear reddish in winter. They begin to turn yellow in March just before they extend into long, yellow pollen-bearing flowers. The female flower buds are small and drooping just ahead of the catkins on the branch. They look like miniature unopened versions of the seed-bearing fruit they’ll become. Last year’s woody fruit, or “cones” are also present, having opened and had their seeds, or winged nutlets, dispersed by the wind last fall.

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Striped Maple Buds

3-11-14 striped maple terminal bud 132Striped Maple (Acer pensylvanicum), also known as Moosewood and Moose Maple, can easily be identified summer or winter by its greenish bark bearing vertical white stripes (hence, its common name). Because the bark is so distinctive, one needn’t rely on Striped Maple’s buds for identification purposes, but they are well worth investigating, nonetheless. Their graceful shape, smooth surface (few bud scales) and pinkish-red coloration distinguish them from all others. These buds and young branches that bear them are devoured by rabbits and hares, are frequently eaten by porcupines and beavers, and provide browse for deer and moose.

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