Tree Party Express III – Final of 3 Series

205Although I will readily admit that I am expressing a fully illogical, wholly aesthetic reaction to a group of trees that perform innumerable keystone roles in their ecosystems, I cannot help but feel that, at the expense of the oaks, the American beech got all the looks in the family Fagaceae.

Genuine querciphiles will take me to task, but even to my fairly well-practiced eye, the oaks are as a group the most subtly differentiated – and thus, difficult to identify to the level of species – of all our native trees. If the birches may be likened to the Neville Brothers, the oaks could as well stand in for the Osmonds, because in parts of our area, one may indeed encounter at least as many species of oak as there are ivory-toothed, harmonizing Utahn siblings.

And not unlike dental records, the surest and quickest way to key an oak to species is by examining its acorns, each of which has a signature unique to its respective species. However, acorns are hard to come by when the ground is buried under feet of snowpack, and twigs are often out of reach as well. In winter, one must posit educated guesses at the identity of individual oaks based on other clues, such as bark, habit, habitat, and elevation.

The native oaks are easiest to identify by bark alone when they occur in pure stands, which, among all our indigenous deciduous tree species, the oaks are most apt to do. Part of the difficulty in seeing and identifying oaks in a mixed forest setting comes from the prejudices we associate with certain storied species. More often than not, the iconic tree we envision when thinking of oaks is the English oak (Quercus robur), admittedly the most visually memorable member of the genus, but still, it’s a sort of ironic cultural hangover, particularly given the broad diversity of North American species of oak. Even if we are familiar with the forms, habits, and haunts of some of our native American oaks, we usually imagine them as open-grown specimens, when, like maples, they can turn into colossal trees. However, even the most recognizable of the oaks, the pin oak, (Quercus palustris), whose unmistakable and efficient branching habit graces many a late twentieth-century carpark, assumes an entirely different visage given the competitive stresses of the forested setting.

Red Oak

Of course, as is the case with even the most difficult genera, the most prevalent species is always the easiest to identify. Among the native Quercus, red oak (Quercus rubra) plays this role predictably, but capably nonetheless, as the species that is most widely distributed throughout the varied micro-environments to be found in our ecologically diverse region. While most often found in acidic woodlands, red oak often dominates south-facing slopes with rich soil of varied chemistry. Red oak has dark gray bark that becomes roughly furrowed, with raised, scaly ridges. With advanced age, the eponymous red underbark is exposed, a dead give-away of its identity for anyone who has ever struggled to light a batch of flatlander firewood. Once again, this species provides another instance in which location, location, location, makes all the difference; for of the ten species of oak native to Berkshire County, red oak is the sole species of oak found on the Berkshire Plateau, and never at high elevation, essentially disappearing as the presence of balsam fir and red spruce increases in the landscape.

White Oak

White oak (Quercus alba), the second-most common oak in our region, is widespread throughout South County in dry woodlands, with a similar species, swamp white oak, occurring in fewer numbers along streams and in wet woodlands. White oak, and the white oak group at large, generally bears gray, shallowly and finely fissured bark that breaks when mature into loose scaly plates or ridges that contrast markedly with the deeply furrowed, generally dark-colored bark of the red oak group. Swamp white oak is the oddball of the group, developing a scaly texture similar to white oak, but unlike that species, the bark breaks to form deep fissures between ridged plates. Other members of the white oak group that may be encountered in the wild with occasional to rare frequency include bur oak (Quercus macrocarpa), chestnut oak (Quercus montana), chinquapin oak (Quercus muhlenbegii), and dwarf chinquapin oak (Quercus prinoides).

HortTopic: Plantings Under Oaks

All trees present challenges to the shrubs and perennials that one might wish to grow under them, but several species produce conditions and issues that require customized remedies. Maples, for instance, colonize the soil with a prodigious number of fine, shallow roots; while black walnuts secrete allelopathic compounds that suppress both germination of seeds and vegetative growth in many shrub and perennial species.

Likewise, oaks are not always overly welcoming of understory companions. Unlike maples, oaks do not have shallow roots, but like pines, they tend to monopolize water resources and produce foliage that decomposes at a relatively slow rate, producing a slightly acidic soil environment over time. The latter issue is not particularly significant, especially given the fact that excessive acidity is a rare complaint in our area; far more cultural problems are associated with excessive alkalinity.

For the greatest degree of success, one ought to consider native perennials that are frequently associated with oaks: Pennsylvania sedge (Carex pensylvanica), Allegheny spurge (Pachysandra procumbens), and Canadian ginger (Asarum canadense) are but a sampling. Nearly any kind of hardy fern will thrive in an oak woodland environment, while ephemerals such as purple trillium (Trillium erectum) often establish extensive colonies in the niches created by stands of red oaks.

Screen shot 2012-08-01 at 5.31.36 AMAlthough most perennials that will thrive in dry shade will do well under oaks, one ought to further refine the plant palette with maintenance in mind. If the space is to be largely cleaned of fallen leaves annually, one can install any plants that fit that basic requirement. In more naturalistic areas, one needs to bear in mind that accumulating leaves will smother most perennials under a foot in height. Exceptions to this rule include woodland ephemerals and bulbous plants that have evolved to rapidly penetrate layers of organic material in their race to flower and propagate themselves before the canopy closes, refoliated for another season.

Black Oak

Black oak (Quercus velutina) is in the red oak group, or rather, red oak is in the black oak group – the oak groupings are more driven by lumber grading than taxonomy – but regardless, it is the third-most common oak in our area, most often found on dry hillsides. Like red oak, its young bark is smooth and dark gray, maturing to form large blackish ridges deeply furrowed to reveal yellowish inner bark. Where they happen to co-exist, one must rely more on variations in acorn and bud morphology to differentiate the two species. Other members of this group that may be encountered in small populations in our area include the northern pin oak (Quercus palustris), scarlet oak (Quercus coccinea), and scrub oak (Quercus ilicifolia).

Reader Question:

Why does snow melt in expanding rings out from tree trunks? -submitted by J.W. Thomas, Windsor, MA.

Occam’s razor, also called the lex parsimoniae (the law of economy), is the somewhat obtuse title given to the truism that the simplest explanation to any unexplained phenomenon is usually the correct one. The most likely cause of seemingly early snowmelt around trees is the interaction between reflective and absorbent surfaces. Snowpack reflects sunlight onto bark, which absorbs the light, producing heat, which melts snow immediately around the trunk. Radiational cooling of the trunk at night extends the process so that it appears more or less continuous.

Of course, this explanation does not exclude the contribution of minor co-factors – such as the effects of meltwater running down trunks or the heat produced by the metabolic activity of the tree itself – but the preponderance of the evidence surrounding the phenomenon clearly points to the simplest explanation: these rings occur most often around single trees or trees in woodland edges and are most common once the light strengthens after January; are most prominent around large, dark-colored trees; and although consistent in margin, are always centered on the face of the trunk that receives the greatest solar exposure.

Maples, particularly larger specimens, tend to produce larger rings and seem to do so before other trees, a red herring that might lead one to believe that the phenomenon must be produced by the heat of rising sap – after all, these rings appear right around sugaring time. However, the difference between a maple and, for instance, a young white pine is one of surface area. Plated bark, such as that of maples, has a far greater capacity to capture and radiate thermal energy than smooth bark, such as occurs on young pines, thus augmenting the melting of nearby snowpack.

True Rarities

One other member of the beech family occurs frequently throughout our region, although few people notice it nowadays due to its diminished state and impoverished role in the landscape. Once a vital source of food for wildlife, and a climax species throughout the eastern forest with seemingly endless commercial applications, the American chestnut (Castanea dentata) was not extirpated by the fungal blight introduced in 1904, but it was nonetheless neutralized by the disease. Like the American elm, young chestnuts are unaffected by blight, but unlike the case with Dutch Elm Disease, the blight kills all top-growth before sexual maturity, resulting a repeating cycle of rapidly growing and precipitously dying stump sprouts. Since the sprouts of chestnut are as smooth-barked as most saplings, they can be quite difficult to identify out of leaf.

AmChestnutBoleDepressing as the story of the collapse of the American chestnut may be – for it was an early casualty of globalization – there is now reasonable hope for the future of the species and its role in the American landscape, due in large part to the efforts of the American Chestnut Foundation. Since its inception in 1983, the Foundation has sought to produce a highly disease-resistant American chestnut by breeding our native species with its Chinese counterpart (Castanea mollissima), and then backcrossing the resulting offspring with pure American stock in order to remove all traits of the other species except for disease resistance. With plans underway to establish production orchards for the purpose of future introduction into the wild, the American chestnut may in fact enjoy a rare second-act, thanks not to gene-splicing but rather to the gentler manipulations of plant breeding that remain unchanged from the day when Gregor Mendel opted to play with his peas rather than eat them.

However, every once in a long while, one stumbles – sometimes literally – across something so exceedingly rare, that it seems the most likely way of having found it was accident itself. Such is the sentiment that possessed me upon the entirely casual revelation of a mature, healthy American chestnut growing within a quarter-mile’s walk from my doorstep, discovered by no other tactic than moving at an animal pace and maintaining open reception to perception. Perhaps this tree, like others said to keep vigil in these woods, keeps dodging the inevitable infection that will eventually lay it low; or perhaps this tree and its ilk possess quirky genes that allow them to scoff at pandemics. Whatever the case, its secret is safe with me.

The Takeaway

Becoming intimately familiar with our trees is the first step to understanding our varied forest communities and the panoply of organisms that depend upon them – not to mention our own species’ varied ethnobotanical traditions centered on woodland plants small and great, from rhizomes and tubers to wood and sap, the respective flesh and blood of trees. While an even cursory investigation of the place that forests occupy in our history and culture quickly reveals that the story is about so much more than lumber, syrup and nuts, when one begins to look a bit deeper into the subject, it becomes clearer still that trees, and more importantly, healthy, unfragmented forests, are the key to restoring a world that has fallen out of equilibrium.

And while learning about our surroundings is enjoyable and enlightening, perhaps this exploration begins to get at the nut of why we find plants in general, and trees in particular, so very bewitching: unlike we animals, trees exhibit various stages of growth in simultaneous harmony; while they titans be, some part of them is always but an infant. It is not too far a leap to suggest that somewhere within us burns a bit of envy for creatures that seem to continuously renew themselves, and can boast some part of their appearance that still resembles that of their youth, without the intervention of a surgeon’s scalpel or Faustian bargain. We must take comfort in the idea that perhaps our inability to access the willow’s indomitable vitality produced the compromise that enabled us to roam the world and cultivate our minds to our wills’ content, shackled only by the scope of our inspiration and imaginations.

By Terrence Trapp, Director of Horticulture

January 2nd, 2012

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