Witches’ Brooms
If you’ve ever seen a tree or shrub that looks like its growth has gone haywire in one particular spot, you may have come across a phenomenon called Witches’ Broom. Witches’ Broom is defined as an “abnormal brush-like cluster of dwarfed, weak shoots arising at or near the same point.” This deformed mass of twigs and branches occurs in response to pathogens and insect pests (mites, aphids, nematodes, fungi, viruses, bacteria and phytoplasmas (parasitical bacteria)) as well as stressful environmental conditions.
Susceptible plants include alder, serviceberry, birch, cherry, elm, fir, hackberry, honey locust, juniper, red cedar, mulberry, oak, ash, willow and spruce, among others. Often Witches’ Brooms are relatively small — a foot or so in diameter. The one pictured required multiple years of growth to reach its current size. Most Witches’ Brooms are not fatal, just disfiguring.
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Red Bark Phenomenon
In the past five years an odd phenomenon has been observed on the bark of over twenty species of trees in New England — an intense reddish-orange coloration. It’s been determined that this is due to the presence of a microscopic green algae (Chlorophyta), tentatively identified as belonging to the genus Trentepohlia. A branching mat of thick-walled algal cells containing a bright orange-red pigment alters the color of the bark.
Red Bark Phenomenon is especially prevalent on White Pine, Eastern Hemlock, Red Oak and American Beech trees. Affected trees appear to be of varying ages and are often, but not exclusively,observed near bodies of water, such as swamps and rivers. Frequently (as pictured) only one side of a tree is affected.
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Next Year’s Buds Already Formed
Because tree buds tend to swell and increase greatly in size in the spring, this is often the season when we first notice them and assume that this is when they are produced. However, if you look in the axils of leaves on any deciduous tree right now, you will see full-size buds that were formed this summer. These little packages of miniature leaves, branches and sometimes flowers, will remain on trees all winter, tightly closed and often protected from the elements by modified leaves called bud scales. Come spring, when trees are once again taking up quantities of water, their buds will swell, scales will fall off (leaving bud scale scars), and tiny, pristine leaves or flowers will appear. (Photo is of American beech, Fagus grandifolia, bud.)
Just a quick reminder that the NC Calendar ordering deadline is November 10th.
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Basic Botany: Bud, Leaf and Branch Arrangement
In winter it is common to use the pattern by which branches and buds are arranged on a deciduous tree as a first, quick clue to the tree’s identity. There are two large groups of trees, those with alternate and opposite patterns, and a third less common pattern, whorled. Trees with alternate arrangement have only a single leaf/bud/branch attached at one location (node) on a branch. Those with opposite arrangement have two leaves/buds/branches attached at a node, opposite one another on either side of the branch. When more than two leaves/buds/branches arise from a node (rare) this is called a whorled arrangement.
At this time of year, when deciduous trees are bare, you can see the arrangement of buds, branches and leaf scars (where leaves have fallen off) clearly. Relatively few trees have opposite branching – Maples, Ashes, Dogwoods, and Horse Chestnuts – while a majority have alternate branching. More characteristics are needed to narrow a tree down to species, but noting its arrangement is an easy and quick way to eliminate certain species.
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Striped Maples Flowering
Striped Maple (Acer pensylvanicum), named after the vertical white streaks on its bark, is often associated with Moose and White-tailed Deer, both of which feed on its bark. In some places it goes by the name “Moosewood” for this very reason. The shape of its leaves give it another common name, “Goosefoot Maple.” In the spring when Striped Maples are nearly in full leaf, bright yellow bell-shaped flowers appear on long, pendulous strings, or racemes. (The flower stalks of the similar Mountain Maple also materialize after the leaves have matured, but these flower clusters are upright, held above the surrounding leaves.)
Striped Maples have the unusual ability to change sexes repeatedly over their lifetime (as does Jack-in-the-Pulpit), a phenomenon called gender diphasy. Among five study populations located in New Jersey, approximately one in four trees exhibited a change in the sex of its flowers between flowering seasons. The flowers of most Striped Maples are predominantly male. If changes occur in the canopy and new conditions seem favorable, a predominantly male tree can become predominantly female (and vice versa, if conditions deteriorate). Size, injury, and carbohydrate reserves are thought to impact the frequency and direction of gender change. Another unusual trait of Striped Maples is that the final sex of a flower is determined within one month of flowering, in contrast to most woody perennials which set buds the previous year.
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White Ash Flowering
In 1935 Walter Rogers wrote a book on tree flowers (Tree Flowers of Forest, Park and Street) in which he described White Ash (Fraxinus americana) in the following words. “The Ashes are important trees with interesting features of form and foliage, but their flowers are among the least interesting.” I am of a different opinion, at least regarding White Ash’s male, or staminate, flowers.
White Ash is dioecius – individual trees have all male or all female flowers. Just before and as the tree is leafing out, the flower buds, located on the shoots of the previous season, begin to open. Male flowers are more noticeable than female flowers, partly because of the size of their clusters — there are between 200 and 300 flowers in each cluster – and their vibrant color (which resembles the fall color of some White Ash leaves). Being wind-pollinated, White Ash’s flowers lack petals as they would impede pollination. The stamens are a purplish-red, raspberry-like color until they mature, at which time the pollen’s yellow color is predominant. The flowers are soon hidden by emerging leaves, so now is the time to see if you agree with Mr. Rogers!
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Distinguishing the Hornbeams
There are two trees, both in the Birch family, which, due to the similarity of their common names, are occasionally mixed up with each other. One is known as American Hornbeam (Carpinus caroliniana) and the other as American or Eastern Hophornbeam (Ostrya virginiana). Due to the hardness of their wood, they also both go by the name Ironwood, adding to the confusion. A perfect example of when Linnaeus’s binomial system, which gives each species two scientific names, one of which is unique to each species, is helpful.
While the fruits and leaves of both species are superficially similar, their respective bark is very different. Carpinus caroliniana’s bark resembles flexed muscles (see https://naturallycuriouswithmaryholland.wordpress.com/2012/10/30/american-hornbeam/ ), earning it yet another common name, Musclewood, while Ostrya virginiana’s bark (pictured) has a “shreddy” appearance, with the bark broken into small, narrow plates which curve away from the trunk. Look for C. caroliniana in valleys and along streams, and O. virginiana on well-drained slopes and ridges.
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Partridgeberry Fruit
Partridgeberry (the fruit is eaten by partridges, or ruffed grouse, as well as wild turkey, mice, foxes, skunks and deer) is a woody vine found creeping along the forest floor, often in large colonies. At this time of year there are bright red berries interspersed among the paired evergreen leaves. If you look closely at a berry, you will see two indentations at its tip. These are the result of the flowers’ unusual structure and the fruit’s development.
In late spring a pair of white flowers appears which share a set of sepals. Each small, fragrant flower has four white hairy petals that join to form a tube. The unusual aspect of these flowers is that they both must be pollinated to obtain a single berry. Each berry is the result of the fusion of the ovaries of the pollinated pair of white flowers. This fusion is what accounts for the two indentations on the surface of each fruit.
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Witch-hazel Cone Gall Aphids Laying Eggs
At this time of year there is a species of aphid, Hormaphis hamamelidis, that is laying eggs on Witch-hazel branches. Next spring female aphids will hatch out of these eggs and begin feeding on newly-emerged Witch-hazel leaves. The aphids inject the leaf with a substance that causes the leaf to form a cone-shaped growth, or gall, around the insect, providing it with both food and shelter. The galls are hollow, and have openings extending out through the leaves’ lower surfaces. Within the galls the unmated female aphids produce 50 – 70 young. Eventually the galls fill with winged female aphids which emerge through the cone openings, disperse, and repeat the process. The third generation of aphids consists of both males and females which mate and lay their eggs on Witch-hazel. The aphids that hatch from these eggs create the conical galls found on Witch-hazel leaves.
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Abscission Layers Forming
As the days grow shorter and the nights longer, cells near where a leaf’s stem joins a tree’s branch start to divide rapidly. This is the start of the creation of the corky layer of cells known as the abcission layer.
The annual growth of a tree ends with the formation of the abcission layer. This layer prevents the transport of materials such as carbohydrates from the leaf to the branch and it blocks the flow of minerals from the roots into the leaves. Chlorophyll, critical to the process of photosynthesis, breaks down with exposure to light and is replaced continually by the leaves during the summer. When the abcission layer forms, this is no longer possible. The chlorophyll slowly breaks down and disappears, revealing the underlying xanthophylls (yellow pigments) and carotenoids (orange pigments) that the chlorophyll was masking. These pigments, in addition to the red pigments (anthocyanins) that are manufactured from sugars trapped in the leaf, provide us with our brilliant foliage.
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More Buds
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
Much 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
A 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
Warming 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.
White 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
Speckled 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
Striped 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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Bitternut Hickory Buds
Habitat, silhouette, bark and buds can all be helpful when identifying a tree in winter. Occasionally a species has one characteristic that is so distinctive, it serves as a diagnostic feature. The sulfur-yellow coloring of Bitternut Hickory (Carya cordiformis) buds is such a characteristic. Both lateral and terminal buds have a powdery coating which gives them a bright yellow appearance. Look for Bitternut Hickory on moist lowlands (hence, its other common name, Swamp Hickory) and rich uplands. Although humans find the nut of this hickory inedible, the smoke produced by burning its wood produces the best “hickory-smoked” hams and bacon.
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Pileated Woodpecker Sign
Pileated Woodpeckers typically make rectangular holes in trees in order to reach the carpenter ants that live in galleries they’ve created deep within a tree. While ants are high on a Pileated Woodpecker’s list of preferred food, wood-boring beetle larvae are not far behind. Sometimes the exertion of jackhammering isn’t necessary in order to reach insect larvae – removal of the outer bark is enough to expose tasty morsels.
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Shagbark Hickory Nuts Ripening
Shagbark 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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Japanese Barberry Invading
Japanese Barberry, Berberis thunbergii , is very much like the shrub Burning Bush, Euonymus alatus – it comes into its own in the fall, turning many shades of red and orange, and thus has had great appeal as an ornamental. Birds, including turkeys, grouse, mockingbirds and waxwings, find the fruit of this woody shrub irresistible, and spread the seeds far and wide – a bit too far and wide, in fact. Like Burning Bush, Japanese Barberry has escaped from cultivation and is established and reproducing in the wild so successfully that it is classified as invasive. It is a particular threat to open and second-growth forests. An established colony can eventually grow thick enough to crowd out native understory plants, reducing wildlife habitat and forage, thereby increasing pressure on native plants by white-tailed deer and other herbivores. According to Pennsylvania’s Dept. of Conservation and Natural Resources, Japanese Barberry also acts as a nursery for deer ticks, which can transmit numerous diseases.
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Poison Ivy Thriving
Poison Ivy is in the Anacardiaceae family, which also includes cashews, mangos and sumacs. The sap of the stems, roots, fruit and leaves of many species in this family contains urushiol oil, which is what causes the allergic rash in 80% of humans that come in contact with these species. Poison Ivy is very sensitive to carbon dioxide, and even slightly elevated levels of CO2 have proven to increase its growth. In the past 50 or 60 years, during which time the amount of carbon dioxide in the atmosphere has increased by roughly 22%, Poison Ivy’s growth rate has doubled. The amount of urushiol oil has not only increased, but it is also more potent…leaves of three, let them be.
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Wild Cucumber Fruiting
Looking more like a miniature spiny watermelon than a cucumber, the fruit of Wild Cucumber (Echinocystis lobata) grows on an annual vine that can reach a length of 15 to 25 feet. The genus name Echinocystis comes from the Greek echinos for “hedgehog” and cystis for “bladder”, appropriately describing the prickly fruit. The puffy, spherical-to-oblong, green fruits with long, soft spines grow up to two inches long. Despite its common name, Wild Cucumber fruits are not edible, and can cause burning reactions in some people. When ripe, the fruit turns brown and dries up, bursting open at the bottom, ejecting four large, flat, black seeds.
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Partridgeberry Flowering
In many areas the forest floor is now carpeted with flowering Partridgeberry (Mitchella repens), the creeping, woody vine found in both deciduous and coniferous woods. The pairs of white flowers occur in two forms. In the first form (pictured) the pistil is short and the stamens are long; in the second form the pistil is long and the stamens are short. This structure prevents each flower from fertilizing itself. Both flowers must be pollinated to obtain a single scarlet berry. Each berry is the result of the fusion of each ovary of the pollinated pair of white flowers. As such, each berry has two bright red spots on its surface.
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