Guest Contributor: Georgia Silvera Seamans, Founder, Local Nature Lab; Director, Washington Square Park Eco Projects
All photos courtesy Georgia Silvera Seamans
Winter is the most wonderful time of the year to notice some of the features of deciduous trees that are overshadowed by showy flowers and brilliant autumn leaves in other seasons. Bark! Buds! It’s always easier to identify species like Platanus x hispanica or Betula nigra at a glance because of their striking bark. However, other trees require a slower gaze to pick out less ostentatious bark. Coming to a standstill and looking closely is required for buds cosseting future leaves and flowers.
With the fall of deciduous leaves, evergreen plants take center stage in the winter. In contrast to the incredible range of broadleaf types, the expressions of needle-leaf species are less diverse, so it’s easier to identify coniferous trees, at least, in terms of their genus. Abies (fir), Picea (spruce), and Pinus (pine), for example. Have you noticed how rhododendrons curl their leaves in winter? The leaves resemble needles. The curling strategy reduces the leaf area exposed to cold air. A Juniperus virginiana is unmistakable in winter: lush, with blue-colored, berry-like cones. Actually, fruit is a useful ID clue in winter — but this topic is for another article!
I don’t claim to be able to identify every tree in the landscape in the summer, much less in the winter. I am still learning about trees’ expressions in all seasons (and stages). There’s so much to learn about winter tree ID that many people have written books about the topic! A classic is Winter Botany: An Identification Guide to Native Trees and Shrubs, by William Trelease. While not marketed as a winter tree guide, Bark: A Field Guide to Trees of the Northeast by Michael Wojtech also focuses on the most conspicuous feature of deciduous trees in winter.
In Bark, Wojtech breaks down bark biology and provides a typology of bark types. Wojtech defines bark as “everything outside a thin ring of tissue called the vascular cambium.” The vascular cambium is responsible for annual growth rings, xylem (water pipes), and phloem, aka inner bark (sugar and nutrient flows). Phloem is the innermost of the two major layers of bark. The second primary zone of bark is the triple-layered periderm. The response of the periderm to wood growth determines the bark type we see. Trees present us with seven types of bark: peeling horizontally in curly strips; lenticels visible; smooth, unbroken; vertical cracks or seams in otherwise smooth bark; broken into vertical strips (length is at least three times width); broken into scales or plates; and with ridges and furrows. The latter is further divided into intersecting; broken horizontally; and uninterrupted.
Once the ornamental cherries have dropped their jaw-dropping flowers, I can focus on their bark lenticels. Especially pronounced in the species Prunus serrulata ‘Kwanzan’, the orange lenticels resemble pursed lips. New Yorkers dread the sidewalk “litter” of the Styphnolobium japonicum’s faded flowers and seed pods. I look forward to finding young trees with pronounced blonde lenticels on pale gray bark.
We don’t need alligators in NYC. Look at the bark of a Cornus florida — the small scales are practically reptilian.
Twigs have bark too. The twig bark of the Liquidambar styraciflua, sprouting corky ridges, is a great winter field mark for this species. There is a grove of Carpinus betulus in Washington Square Park. Not too far from the park are native hornbeams. Carpinus caroliniana doesn’t make joining the gym a New Year’s resolution. Their bark skin is always toned!
More Metasequoia glyptostroboides and Taxodium distichum than ever are being planted in parks and along sidewalks in the city. Both conifers are deciduous, so bark clues are key to winter identification and differentiation. The species are “look-alike cousin[s],” writes Arthur Plotnik in The Urban Tree Book, but their bud arrangements are different (see next paragraph). Their bark is also dissimilar. Metasequoia glyptostroboides’ russet bark peels in thick, uneven, vertical strips. On the other hand, Taxodium distichum has more brown in its bark, and although the bark peels, the strips tend to be thinner and narrower.
Another feature to use in winter ID is the bud. An important first step is to discern if the buds are oppositely arranged (directly across from each other on the twig) or alternately arranged. There are a handful of woody plant species with opposite bud/leaf arrangement: maple, ash, dogwood, honeysuckle and horse chestnut (the pneumonic is MADCapHorse). If your tree has oppositely arranged buds, you can focus on a shorter list of species. You can also start by looking at the features of the buds. Do they appear seamless? Do they have overlapping scales? Are they fuzzy? Are they large and sticky? Your answer to these questions can help you refine the number of species you have to consider. It can be hard to photograph a bud well. Trelease, author of Winter Botany, uses black and white drawings of twigs to show the intricacies of the bud, leaf scar, and pith.
I really enjoy looking at dormant buds. I love getting even closer than usual to trees to peer at these structures that protect the potential of next year. The look and feel of magnolia buds are like no other. I visit the Magnolia stellata and M. x soulangeana in Washington Square Park throughout the winter. There isn’t an Aesculus hippocastanum in the park, which is fine—I am rooting for a Celtis occidentalis—but if there’s a horsechestnut near you, I recommend touching the terminal buds. You won’t mind the stickiness factor. I always admire the clusters of buds at the terminal end of oak stems. The buds match the lobes! White oaks have rounded buds while red oaks have pointed ones.
My favorite tree is Liriodendron tulipifera. I love everything about this species. Its bud is composed of two dusky purple scales that meet seamlessly and resemble a duck’s bill.
My tree familiars are Northeastern species. To hone in on trees and other nature in the region, I choose regional field guides. If you are seeking a guide to Eastern trees for all seasons, consider Identifying Trees of the East by Michael D. Williams. The book has all the essential information and hits a visual sweet spot with photos of leaf, flower, fruit, bud and bark.
A tree is more than any of its parts. A tree is a being unto itself. A tree sustains others, whether lichen or wasp larvae or sapsucker. Most times learning to identify a tree is reduced to its leaves. Let’s consider other ways of getting to know our local trees. I hope this short article has inspired you to give trees a second look in the winter.