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Bark

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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Porcupine Artistry

1-5-16 porcupine incisor marks  634The patterns that a porcupine’s incisors leave when a porcupine has been removing bark down to the cambium can be a work of art. The way in which a porcupine makes these patterns is as intriguing as the patterns themselves. “The porcupine removes the bark in small triangular patches, each patch composed of five or six scrapes converging on an apex, like sticks in a teepee. The apex represents the position of the upper incisors, held fixed against the bark. The lower incisors scrape, moving over a fresh path as the lower jaw swivels in a narrow arc.” (Uldus Rose, The North American Porcupine) Fortunately, porcupine incisors, like those of all rodents, grow continually. Even though each incisor loses 100% of its length to wear in a year’s chewing, its length always remains the same. Juvenile porcupines leave a much less “organized” set of incisor marks (overlapping, randomly placed) than adults.

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Black Cherry – well known to most readers!

black cherry tree silhouette IMG_5114Black Cherry, more than most tree species, often has several identifying features even after it loses its leaves. The buds of Black Cherry have about ten scales, each of which is brown at the tip and green at the base. The bark of young Black Cherry trees is typically smooth, reddish in color and covered with grayish, horizontal lines called lenticels — small openings that allow the passage of gases in and out of the tree. The bark on older Black Cherry trees consists of squarish scales, curved outward at their vertical edges, somewhat resembling burnt potato chips. Black Cherry is one of several trees on which the fungus Apiosporina morbosa causes Black Knot Galls. Lastly, Black Cherry is the primary host for the Eastern Tent Caterpillar moth. These moths encircle Black Cherry branches with their egg masses, and the eggs hatch just as Black Cherry’s leaves emerge from their buds, providing food for the young larvae.

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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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Living Hollow Trees

12-31-14 hollow yellow birch 027Occasionally one comes across a living tree with a portion of its trunk, or its entire trunk, hollow. How is it possible for a tree to thrive even when its center, or heart, has completely decayed? It comes down to the different kinds of wood that are produced by a tree: sapwood and heartwood.

Sapwood (often light-colored) is the younger, living, outermost portion of a woody branch or tree trunk (just beneath the bark), while heartwood (often dark-colored) is the dead, inner wood. All wood in a tree is first formed as sapwood. Sapwood’s principal functions are to conduct water from the roots to the leaves (via xylem tissue) and to disperse nutrients made by the leaves to the rest of the tree (via phloem tissue). Heartwood (so called because of its central position, not because it is essential to the health of the tree) is basically non-functioning xylem tissue that has become blocked with resins, tannins, and oils. Although the dead heartwood can lend stability to a tree, it is no longer part of the transport system, and therefore, not vital to the tree.

Cavities and hollows typically result from an injury to a tree (usually caused by fire, storms, lightning, insects or birds) that exposes the heartwood. Bacteria and fungi lose no time moving in and beginning the decaying process, which can result in a hollow tree. Because the sapwood, and therefore the transport system, is still intact, the tree lives, despite the loss of its inner heartwood.

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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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Shagbark Hickory Nuts Ripening

11-19-13 shagbark hickory 043Shagbark Hickory, Carya ovata , a member of the Walnut family, is named after the shaggy appearance of the bark on older trees. Shagbark Hickory produces nuts which initially are covered with thick husks. As time goes on, the green husks turn brown and open, exposing the nuts, which fall to the ground if squirrels haven’t managed to eat them while they are still on the tree. It takes about ten years for a Shagbark Hickory tree to start producing nuts, but large quantities are not produced until it’s 40 years old. Nut production continues (a good crop every three to five years) for at least 100 years. Shagbark Hickory nuts are very sweet and highly nutritious. They were a staple food for the Algonquians and squirrels, raccoons, chipmunks, mice, bears, foxes, rabbits, wood ducks and wild turkey also feed on these excellent sources of protein, fats and carbohydrates.

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