Tree Party Express I: First of 3 Series

100Whether you ski, snowshoe, hike, or simply go for a regular walk, the winter landscape presents unique opportunities to observe and learn about our native ecosystems, of which, in the largely reforested northeast, trees can be said to be the cornerstone. However, many of our wooded areas are so dense in growth that for much of the year, foliage severely delimits the observer’s depth-of-field, sometimes to only a few meters in any direction, setting a formidable obstacle in the development of an understanding of the composition of the forested landscape, and with it, the information that particular communities of trees reveal about the geology, hydrology, and ecology of their locales.

Winter offers an opening, both literal and figurative, into the world of the forest and its constituents. In the absence of the relatively more facile identifiers of foliage and flower, however, we must often rely on the somewhat more esoteric – but hardly unlearnable – qualities of bark, twig and bud in order to give names to the various august presences that populate the sleepy west of the woody east.

Bark, the living skin of trees, is likely the most compelling and easily accessible of the lesser used identifiers. That said, one must also look to other clues to compensate for the fact that the texture, pattern, and color of bark change over the life of a particular species more often than they do not.

In some species, bark develops in such a manner that a common thread can hardly be found in the appearance of young, middle-aged, and mature tissues. However, one can very clearly see the transition if one scans the trunk from the top of the crown down to the trunk flare, a practice that is very helpful in distinguishing not only very similar species but also what may be called false cognates, unrelated species that can mimic each other at divergent stages of development. For instance, viewed only at eye-level, a middle-aged striped maple could easily pass for a mature downy serviceberry, but scanning the trunk will reveal the truth, since striping becomes more prominent with age in the serviceberry but more subtle with age in the striped maple, which more resembles its kin as it matures.

Easy Identifications

Evergreen Conifers

Of course, the easiest of all trees to identify in the winter landscape are those which still retain a large proportion of their foliage past autumn: the evergreen conifers. To add to the luxury of having foliage at one’s disposal as an identification tool, the process of elimination is facilitated by the fact that the number of species of native and introduced conifers found in our area composes a brief menu relative to the diversity of indigenous deciduous species. Moreover, in some instances there is but one commonly found representative of an entire genus, e.g. Tsuga canadensis, eastern hemlock. As is the case with any other organism, the distribution of each species is indicative of its relative level of adaptability to varied conditions.

Most common among the local evergreens is the eastern white pine (Pinus strobus). While one can find colonies of pitch pine (P. rigida) and red pine (P. resinosa), as well as occasional cultivated stands and windbreaks of scotch, Austrian, and jack pines, if one is a pine in New England, one is more than likely an eastern white pine.

While today’s stands are mere dwarves compared to the giants of the pre-colonial era, the trunks of even middle-aged trees are impressive for their arrow-straight orthodoxy; in their long, tapering forms, one can easily envision the masts of great ships, and instantly understand why, in an age when Europe had exhausted its own resources, the eastern white pine may arguably be the species that most made possible British naval dominance and its resultant Empire.

White pine has smooth gray bark when young and dark, brown, plated bark with deep longitudinal furrows when mature. The bark of red pine features more prominent plating and commonly has some red coloration with maturity, while pitch pine can easily be distinguished from the crowd by the unusual presence of foliage sprouting directly from its dark gray, scaly, deeply furrowed bark.

Eastern hemlock stands out for its very dark brown, scaly bark, which develops thick deep furrows, scaly ridges, and a cinnamon color as it matures.

While a quick glance at a very old trunk might evoke a pine, middle-aged bark resembles that of no other native conifer, and is only similar in texture to black cherry.

Likewise, balsam fir (Abies balsamea), a species whose presence I’m blessed to have grace my property, is one that is easy to identify by virtue of unmistakable brownish-gray, thin smooth bark that becomes scaly only over the most mature tissues.

In addition to its rarity in most of our area, occurring here only in transitional and true boreal forests at high altitude, its unvarying narrow-pyramidal form makes it easy to pick out in a crowd (plus, the scent can’t be beat).

Confusion ‘Round the Spruces

Conversely – and doubly so – identifying a spruce around here ought to be easy, but isn’t. While red spruce (Picea rubra) is the only common native species seen in our area, and again only in montane contexts – black spruce (P. mariana) occurs but is exceedingly rare, requiring not only boreal conditions but acidic, hydric soils to boot – an easy identification is complicated by the fact that the non-native, freely-reseeding Norway spruce (P. abies), has historically been employed in forestry in the region, sometimes in combination with red spruce, with which it may even hybridize. The two species are not easily distinguishable by bark, although there are subtle differences.
Again, this is a case when looking skyward helps, as Norway spruce has somewhat pendulous twigs and longer branches relative to those of red spruce. Still, under the congested conditions of an unharvested timber project, the normal characteristics of either species can be somewhat inhibited by the inherently unnatural level of competition for resources, muddying the visual evidence. In those cases, the truly inquisitive must resort to examining minor differences in the leaves, which I’ll remind you are called needles for a reason – they are really narrow and small! It almost takes me back to my days in entomology, identifying beetle larvae under a microscope by differentiating the pattern and number of hairs on their rear-ends.

A Cedar by any Other Name…

Would Be Preferable!

“Cedar” is perhaps the most misapplied common name in botanical science. At least three different North American genera, all members of the cypress family (Chamaecyparis, Juniperus, Thuja), are commonly – and mistakenly – referred to as cedars, largely through the influence of the marketing of timber products. True cedars, genus Cedrus, are members of the pine family. The only representative of the “false” cedars that one is likely to encounter in our region is eastern red cedar (Juniperus virginiana), perhaps more properly called red cedar juniper.

A species common to lowlands (but almost never encountered north of Sheffield), red cedar juniper is not a forest tree per se, but rather a component of old-field succession, the process by which abandoned agricultural land is reabsorbed into the forest matrix. It is a particularly early pioneer due to the fact that it is rather unpalatable to livestock, and is a common sight in disturbed areas such as the margins of highways. This species is easily identified by its brown, dry, shredding bark which exfoliates in a longitudinal fashion, and is distinguished by its un-ridged trunk from the slightly similar arborvitae (Thuja occidentalis), which though native in some small degree, exists more commonly in our region as cultivated specimens and the scions thereof. Red cedar juniper, while a very useful timber species, is an indispensible food source for many animals, particularly migratory birds.

Live Nude Trees!

Easy Deciduous I.D.s

Unlike most of the species previously mentioned, which generally occur in specific circumstances and niche locations, several easy-to-identify deciduous tree species are nearly ubiquitous in distribution, although most tend to be supporting, rather than predominating members of forest communities. Among these, none is distributed as widely as black cherry (Prunus serotina), an efficient colonizer of woodland vacancies produced via natural or human disturbance. A rapidly-growing tree, its modus operandi is still fully evident at maturity when its growth rate has stabilized: a tall, unbranched trunk, sometimes having grown up in a curvilinear, gravity-defying fashion, still evokes the feverish race to pierce the canopy.

To my eye, once recognized, black cherry can be confused with nothing else. Mature bark is very dark, scaly, and with even greater age becomes fissured to reveal reddish-brown underbark. Bark overlaying youngest tissues is reddish-brown, turning rapidly to a varied dark gray, of a visual quality similar to an India ink-wash, and marked with prominent horizontal, streaked markings (lenticels) that characterize the genus Prunus at large. In fact, if one could array them in some sort of monumentally scaled police line-up, one would notice many direct comparisons between this largest native member of the rose family and the smaller pin cherry (P. pensylvanica), the rare (in our region) wild plum (P. americana), the choke cherry (P. virginiana), and even the cultivated peach (P.persica). Another easy identifier of black cherry – common to many of its relatives – is the presence of black knot, a pathogen which causes the tree to produce strange burls which can grow to the size of a large pumpkin.

American beech (Fagus grandifolia), is the only easily identified native species in a family that includes some of the most difficult, the oaks. By contrast with them, American beech is unmistakable for anything else in the American forest. From top to bottom and from smallest twig to girthiest trunk, the entire tree is clad in thin, smooth, medium-gray bark, and as such is somewhat of an oddity among Nearctic trees. While young, often clonal colonies are common in mixed woodlands, one does occasionally encounter large specimens whose smooth, matte gray trunks suggest nothing so much as the legs of colossal pachyderms. Like its cousin the pin oak, beech trees often retain dead leaves until late in the winter, particularly when young.

Shagbark hickory (Carya ovata) is similarly easy to distinguish due to its rough, gray – and yes – shaggy bark which exfoliates in quite an unusual manner, separating from the surface in long, curving strips attached in the middle. Fortunately, this characteristic is evident in fairly young trees as well as in mature specimens, ensuring quick recognition in a family that features includes pignut hickory, bitternut hickory, black walnut, and butternut, all of which are difficult to tell apart in winter if fallen fruits are not present for examination.

American elm (Ulmus americana), once the king of the American street, is rarely encountered as a large, mature tree in the wild, but since Dutch Elm Disease, endemic since the 1920’s, does not normally affect trees until they have attained at least 6″ bole diameter, the elm remains a common presence in our forests, particularly in the Central Valley. Unlike beech, cherry and the hickories, elms rarely occur on the Berkshire Plateau. Although young trees do not possess the distinctive vase-like habit of the mature giants, they do already display the gray, furrowed, scaly bark that can be confused with few other native trees. Other trees with similar bark – such as ash and cottonwood – have other hallmark features such as coarse texture or large buds that make misidentification unlikely.

The sycamore, or American planetree (Platanus occidentalis), is just about the most dramatic tree to be found in eastern North America. With its smooth, chalky-colored bark, exfoliating in large flakes to reveal varicolored patches of underbark, it is impossible to mistake this species for any other. It is almost exclusively found growing in the alluvial soils of our lowlands, and given a stable streambank environment, is one of those species – like cottonwood – that can grow to simply awe-inspiring proportions.

Another common resident of the central valley, from forest to abandoned lot, is the opportunistic black locust (Robinia pseudoacacia). This species is thought not to be truly native to the area but proliferated from plantings introduced largely for the production and harvest of its highly rot-resistant wood, traditionally used for fence posts, for which purpose it exceeds nearly all other native hardwoods in durability, and compared to which pressure-treated wood products are a joke. Black locust saplings and twigs are pure evil, bearing strong, paired thorns around the leaf scars; they make for an easy identification, whether perceived by sight or by draught of blood. The bark of this species is also quite memorable, becoming dark, crosshatched and deeply ridged, forming massive buttress-like structures in old specimens. Black locust is the largest indigenous member of the pea family (Fabaceae), and like all legumes, utilizes specialized root organs to fix atmospheric nitrogen into a form usable by plants, thereby enriching the soil. While soil enrichment usually has positive connotations, it can sometimes threaten niche habitats such as pine-barrens that only exist in nutrient deprived substrates, producing an odd situation in which this tree, though a native species, has been listed in many states as a noxious, invasive weed.

By Terrence Trapp, Director of Horticulture

December 15th, 2011

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