As winter brightens into spring and we all suffer through the “spring forward” time change, the trees and shrubs in our landscape are beginning to awaken from their winter dormancy. But until bud burst, you can still get out there and learn to recognize more of our Nantucket Flora in winter condition — let’s hope, with gradually warming weather and some pleasant sunny days!
The February Winter Botany forest tree ID blog article was quite popular, so here’s an introduction to some of our local shrubs before they are decked out in leaves and flowers. Since there are many more shrub species on Nantucket than tree species, this article includes only a sampler, and we hope to write about more shrubs in winter condition next season.
A great place to start in getting to know our shrubs is black huckleberry (Gaylussacia baccata), one of the most common bushes of open areas on Nantucket. Like blueberries, huckleberries produce edible fruit prized by humans and wildlife, although black huckleberry fruits are glossy and black, and are a bit less sweet and have larger seeds than their blueberry “cousins.” How can you tell a black huckleberry in winter? Look for large areas of densely growing, upright stems. While black huckleberry twigs can be brown or gray, the upper branches often have a bright red cast that seems to grow more pronounced as winter shifts into spring. Buds on this species are tiny and nondescript, coming to an angled point rather than rounded like those on high bush blueberry. You can find large patches of this clonal shrub growing with scrub oak in the Middle Moors (AKA Serengeti). Clonal shrubs reproduce by sending out underground runners that make new upright stems, so that they often appear as dense patches of growth all of one kind.
Common high bush blueberry (Vaccinium corymbosum) is also abundant and widespread on Nantucket, but mainly in and around wetlands and ponds. High bush blueberry seems to take its name very seriously, growing in tall mounded shapes, sometimes reaching 10 or 12’ tall. Larger “old growth” blueberry shrubs have gnarled, spiraling stems that form interesting contorted shapes with more flaking, textured bark. Like black huckleberry, twigs of high bush blueberry are often bright red, but it’s easy to tell them apart, because high bush blueberry has large plump rounded buds (also often red) that are pointed at the tip. The bud scales that protect the flowers and leaves often have a lighter colored edging so that you can see the individual scales quite easily on high bush blueberry. Note: sometimes the twigs are green or brown, so don’t be fooled by a lack of red–get to know the buds and the growth form of the trunks and branches (top picture).
Sweet Pepperbush (Clethra alnifolia) is also extremely common on Nantucket and found growing in dense thickets ringing ponds and wetlands, as well as in moist forest. The scent of sweet pepperbush’s creamy white flower spikes is most often described as “overpowering or cloyingly sweet.” Sweet pepperbush perfume is strong enough to drown out the smell of the landfill if you are driving down Madaket Road during the short time this species is in bloom! In winter, sweet pepperbush may be confused with neighboring clumps of maleberry (Lyonia ligustrina), but you will find that sweet pepperbush’s woody capsules are neatly arranged on a central stalk, creating a spike-like shape. Each woody capsule has a persistent style that protrudes, making it look more like a bird with a beak, rather than a rounded ball-shaped capsule as in maleberry. Flower clusters of maleberry are irregular, rather than an upright flower stalk.
Often found growing with sweet pepperbush and high bush blueberry is Swamp Azalea (Rhododendron viscosum). Another common name for this species is clammy azalea, for the sticky glands that grow all over its flower tubes. In winter, there is nothing clammy about it, and you will recognize it mainly by the fact that it grows with branches in whorls similar to the spokes on an umbrella. You can also easily recognize the large round buds (much larger than those of the other shrubs discussed here) with pointed tips that contain the season’s new foliage and flowers. The buds are usually tan or greenish, with darker chestnut brown and a white fringe edging each scale. In late spring or early summer, swamp azalea’s white blossoms begin to appear just after sweet pepperbush and offer a lighter jasmine fragrance. Squam Farm, Squam Swamp, and Sanford Farm are great places to view these wetland species along the trail.
Sumac (Rhus copallina, R. glabra, and R. hirta) are clonal shrubs that can rapidly colonize abandoned agricultural fields and vacant lots. On Nantucket they are also found in shrublands, sandplain grasslands and heathlands, though their distribution is patchy and they are not generally dominant species there. Sumacs are highly visible in the fall with their incandescent red or orange foliage, and clusters of fuzzy deep burgundy fruit that top the upper branches. In winter, remnants of the fruit remain, after being picked over by birds and pummeled by the weather. You can also recognize sumacs by their stout twigs and fat buds, which alternate on the stem.
Winged sumac (R. copallinum) is most common on island and may be found growing in large patches at the UMass Nantucket Field Station on Polpis Road. Its leaves have wings along the petiole, and it can be distinguished from other sumacs by the leaf scar, which surrounds the buds only less than halfway. Smooth sumac (R. glabra) has leaf scars that make a U or C shape around each bud, and its twigs are smooth and hairless.
Staghorn sumac (R. hirta), looks much like smooth sumac, except that it has fuzzy twigs, like the velvet on a buck’s antlers. Smooth sumac is found in several locations around the island, while staghorn sumac is quite rare and known to occur in only a couple spots. Interestingly, staghorn sumac is very common and widespread on the mainland.
As with trees, dormant season botanizing to learn shrub ID is a fresh way to see our shrubs in a new light and start to notice the roles they play in our island ecosystem. Plenty of time to get out there before leaf-out!
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If you happen to be wandering through Squam Swamp or Squam Farm as autumn gives way to winter, you may notice that while most of the trees have already shed their foliage, oaks (Quercus spp.) and American beech (Fagus grandifolia) may still retain old dried leaves rattling spookily in the wind. Some individuals seem to remain almost fully dressed, while others have only tattered remnants. This penchant for retaining leaves into the winter is called “marcescence,” and there are a few theories that have been proposed to explain why some trees display this trait and others don’t.
Nantucket Conservation Foundation's Science and Stewardship Department 