Sycamores (Platanus occidentalis), well-known for their patchwork bark, produce their fruit in balls suspended by long stems. The individual seeds clustered into these balls have brown hair-like structures at their base which help disperse them, but dispersal occurs gradually and the fruit often persist through the winter.
Although usually fruiting is prolific every year, there aren’t the number of Sycamores one might imagine sprouting near an established tree. This is in part due to the fact that Sycamore seeds don’t germinate unless they land on very moist soil with lots of sunlight and little competition from other plants. Once established, a Sycamore tree reduces competition by having fruits (and leaves) that produce compounds that inhibit the growth of other plants.
Oaks are generally divided into two major groups: red oaks and white oaks. Red oaks have bristle-tipped leaves, acorns with hairy shell linings and bitter seeds that mature in two seasons. White oaks have leaves lacking bristles on the lobes, acorns with a smooth inner surface that are sweet or slightly bitter and mature in one season.
Bur Oak (Quercus macrocarpa). also called Mossycup Oak, is in the white oak group and is easily identified by the corky ridges on its young branches, deeply furrowed bark and acorns with knobby-scaled caps (cupules) with a fringed edge. This member of the beech family (Fagaceae) derived its common name from the resemblance of its heavily fringed caps to the burs on a Chestnut tree, though the caps only half cover the nut. Common in central U.S., Bur Oak is relatively uncommon in New England, occurring in in central Maine, New Hampshire, the western edges of Massachusetts and Connecticut, and the Champlain Valley in Vermont.
American Basswood (Tilia americana) is known for the alluring scent and abundant nectar of its flowers, as well as its lightweight, odorless wood which lends itself to the production of food crates and boxes, musical instrument parts, yard sticks and cabinets. Equally distinctive are the nutlets that are borne on a stem bearing a persistent bract, or modified leaf, that aids in the wind dispersal of the fruit.
Most of the nutlets are eaten in the fall by chipmunks, mice, squirrels, porcupines and rabbits, but some persist until winter winds detach them from the tree and they fall to the ground. Basswood trees are not as dependent on seed germination as many other species due to their ability to put out new shoots from their stump or roots if cut down or damaged (self-coppicing).
The fruits of the Hophornbeam tree (Ostrya virginiana), also known as Ironwood for its strong, hard wood, are drooping clusters of papery, bladder-like sacs each containing a nutlet. The “hop” portion of its name refers to the resemblance of these fruits to those of true hops that are used in the production of beer. Hornbeam refers to a related European tree whose wood was used to yoke oxen; therefore, its American counterpart wood was also used as a “beam” with which to yoke “horned” beasts of burden.
Tamarack (Larix laricina), also commonly called Eastern or American Larch, grows and drops a new set of leaves every year, just like maples, birches, or other deciduous trees. Found in many bogs, it is the only native deciduous conifer in the Northeast and is known for its green needles which turn a showy yellow in the fall before falling to the ground as winter approaches. Equally dramatic, however, are its seed cones. They are the smallest of any larch (1/2” to 1” long) and have only 12 to 25 scales. At a certain point (right now) in their spring growth they are bright maroon and resemble tiny roses. They eventually turn brown and open to release the seeds, four to six months after pollination.
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.
One species of tree you might encounter if you’re in a floodplain is the Eastern Cottonwood (Populus deltoids), a member of the Willow family and the Poplar genus. Because it can tolerate flooding, it often grows near river banks and disturbed wet areas. The buds of Eastern Cottonwood are large and somewhat sticky, due to the resin that they contain. Resin exudes from the buds during the fall as well as the spring, and is evident even in winter when you see it frozen in droplets on the buds (see photo). In trees, resin serves to seal wounds and defend against bacteria, fungi and insects.
European Honey Bees discovered that the properties of cottonwood resin which benefitted cottonwood trees could also benefit them. They collect the resin from the outside of Eastern Cottonwood buds, mix it with wax and apply it to the walls of their nest cavity. This “bee glue” is referred to as propolis, and, as it turns out, serves as an antimicrobial barrier as well as a sealant. Various bacteria, fungi and other harmful microbes are kept at bay by the resin contained in propolis. It also directly reduces two diseases of Honey Bees, chalkbrood and American foulbrood.
Interestingly, if a mouse or small rodent happens to die inside a hive, and the bees can’t remove it through the hive entrance, they often seal the carcass inside an envelope of propolis. This prevents the hive from being affected by the mouse’s decomposition.
When the inner walls of cambium cells in a Black Cherry (Prunus serotina) tree (and other members of the Rosaceae family) are damaged by insects, enzymes can break down pectin, producing jelly-like lumps of clear sap that appear from beneath the bark. This “gum” is often the result of aborted attacks by bark beetles, particularly the peach bark beetle, for the tree uses it to seal off infection. Both direct feeding by insects as well as the process of egg-laying can cause this phenomenon called gummosis. Other factors, including fungi, stress and physical injury to a tree, can produce this reaction.
Black 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.
Eastern Larch, Larix laricina, is also known as Tamarack, the Algonquian name for the species which means “wood used for snowshoes.” This tree strongly prefers moist to wet sites in acidic soils and is a common sight in northern New England bogs. Eastern Larch is the only species of conifer in New England that drops all of its leaves/needles every year. The needles are borne on short shoots in groups of 10–20 and prior to falling off, they turn a beautiful golden color.
If you’ve noticed yellow clouds near pine trees recently, or a layer of yellow “dust” on your car or pond, you’ve witnessed the annual dispersal of pollen by male pine cones. Light and fluffy so as to be easily distributed by the wind (rather than insects), these minute pollen grains containing sperm cells can be found just about anywhere this time of year, including the nostrils of humans. All pines have separate male and female (seed) cones on the same tree. Male pine cones, which produce pollen, are much smaller, occur in clusters, are more papery, and remain on the tree for a much shorter period of time than most female pine cones. (By July they will litter the ground beneath pines before they quickly disintegrate.) Although it may mean a brief period of sneezing has to be endured by those allergic to it, this “golden smoke” not only creates beautifully intricate patterns for us to enjoy and makes it possible for pine trees to make the next generation of seeds, but it is also touted as an agent of increased testosterone and strong sexual libido, anti-aging, skin rejuvenation and improved immune systems for humans. Haste ye to a natural food store (or the closest pond!). (photo – Red Pine pollen & male cones)
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.
Witch Hazel (Hamamelis virginiana) is nature’s final fanfare of the fall. As colorful fall foliage disappears, the yellow strap-like petals of Witch Hazel’s fragrant flowers brighten denuded woods. These flowers are pollinated by moths that are still active this late in the season, and develop into small, hard capsules that remain dormant throughout the winter. During the following summer, these capsules develop to the point where they expel two shiny black seeds 10 to 20 feet away from the tree. The seeds take another year to germinate, making the length of time from flowering to germination approximately two years. (In photo, the yellowish-tan capsules were formed this summer, and the one brown, year-old capsule has opened and dispersed its seeds.)
The falling of a leaf is the final step in an ordered series of events referred to as senescence. This process allows trees to conserve resources, prepare for a dormant period, and shed inefficient tissues. When leaves become unable to produce food due to a lack of chlorophyll, a process of shutting-down and sealing-off begins. Leaves are shed through a number of biological actions which take place at the base of the leaf’s stem, or petiole. The walls of some cells weaken, while those of other adjacent cells expand. The expansion of the latter causes pressure against the weaker-walled cells, resulting in these two groups of cells tearing away from each other, causing the leaf to fall. The tree forms a protective barrier on the wound where the leaf had been attached to the branch, sealing it off from pests and the environment and leaving a leaf scar.
Even though it snowed in Vermont this weekend, there is something else white and fluffy that is also being blown about, and it doesn’t melt when it hits the ground. The tiny white bits of fluff that are floating in the air are the seeds of aspens (also referred to as poplars), primarily Bigtooth Aspen (Populus grandidentata), that are borne in capsules that develop along a 3 to 6-inch dangling stem. These former flower clusters, and the capsules and seeds they developed into, are referred to as catkins. The capsules split apart when the seeds are mature, releasing the cottony-tufted seeds that are well-designed for dispersal by the wind. Looking into the fluff-filled sky, it’s not hard to believe that a single Bigtooth Aspen tree can produce over a million seeds.
Tree buds are formed in the summer, so if you look at a tree today, it will have buds on it, in the axils of where the leaves used to be (on deciduous trees). There are two kinds of buds – leaf buds and flower buds (flower buds are typically fatter than leaf buds). Both are usually covered with scales which help seal in moisture to protect the bud from drying out during the long, dry winters when water is frozen and therefore unavailable. Different types of trees have different types and numbers of scales. There are a few trees whose buds lack scales completely; these buds are referred to as “naked.” Witch hazel (Hamamelis virginiana), bitternut hickory (Carya cordiformis) and hobblebush (Viburnum lantanoides) all have naked buds. In the photograph, a hobblebush leaf bud is on either side of a flower bud.
American Hornbeam (Carpinus caroliniana) goes by many names, including Musclewood, Bluebeech and Ironwood. Its smooth, gray bark that appears twisted and somewhat muscular is very distinctive. This member of the Birch family usually has several trunks, and is usually less than 30 feet tall. Its fruit is in the form of clusters of small nutlets, each attached to a papery bract. A good seed crop is produced every three to five years, at which time it benefits ruffed grouse, cardinals, evening grosbeaks and American goldfinches, all of whom prefer it over many other seeds.
Witch Hazel (Hamamelis virginiana) is in flower, one to two weeks early this year, just as last year’s fruit is mature and ready to explode, sending seeds flying. This shrub may have gotten its name from its association with dowsing, which was once thought to be a form of witchcraft. (Witch hazel’s branches were once the wood of choice for dowsing rods, whose purpose is to locate water, or “witch” a well.) The bark, leaves, and twigs of witch hazel are all high in tannins, giving this plant astringent properties. It has also been used for any number of medicinal purposes, from treating hemorrhoids to laryngitis.
Many plants practice “delayed greening” of their leaves, including this Red Maple (Acer rubrum). An initial lack of chlorophyll prevents the leaves from photosynthesizing and making food, which means they have little nutritive value, and thus, appeal, to an herbivore. Most plants that delay greening have reddish leaves due to the presence of anthocyanin, a pigment which appears reddish. A majority of herbivorous insects and invertebrates cannot detect colors in the red range of the color spectrum. Young leaves suffer the greatest predation from invertebrate herbivores. Red leaves would be perceived by these leaf eaters as somewhat dark and possibly dead – not a choice food material. It is possible that the red coloration of new leaves allows the plant to make them unappealing to the herbivores that would otherwise eat them.