Here in Boston, after a long and uncharacteristically balmy autumn, it’s finally starting to feel like winter. Before the big storm last weekend, I decided to take a walk around the Arnold Arboretum and photograph some plant anatomy. By the time I reached the Arb, the temperature had dropped well below freezing, dark clouds had moved in, and the first flakes were beginning to fall. Luckily, I was able to spend a few hours wandering around with frozen fingers, and make some decent photographs despite the frigid wind.
Winter is a fantastic time to observe trees. There’s a particular poetry in the image of a mature tree silhouetted against the snow and gray sky. Without foliage obscuring our view, we can observe the history of each plant through its unique growth characteristics, the intricacy of its mature bark, the marks of disease and trauma, and its relationship to nearby organisms. Whatever color remains in the landscape smolders against the wintry backdrop.
We usually think of winter as a time of dormancy, hibernation, and senescence–a moment of pause before an explosion of spring activity. While animals become scarce or disappear completely, and the metabolism of plants slows down dramatically, there is still plenty to see. Evergreens continue to photosynthesize, their foliage protected by waxy cuticles. Many trees and shrubs retain their fall fruit, and provide food for the small mammals and birds that stick around through winter. Most woody species have already produced buds containing the primordia that will become the earliest leaves and flowers of the coming spring. These precious organs are encased in scales and other protective measures that help them survive freezing temperatures and drying winds. Come spring and rising temperatures, these buds will swell and eventually open, releasing the first flushes of flowers and foliage.
Above, the male catkins of the Szechuan filbert (Corylus heterophylla var. sutchuenensis) have bright colorful scales. They formed during the growing season and will wait in dormancy throughout the winter. These catkins are really just clusters of tiny male flowers that will open and release pollen in early spring, before leafout.
Many species of Corylus can be coppiced, resulting in a stand of juvenile saplings as seen in the image above. Coppicing is a technique used for thousands of years to grow long, narrow staves that can be harvested and used in cooking, construction and tool making. It relies on a plant’s particular response to trauma, which causes it to send up a number of sprouts (or suckers) from the base. By continually cutting back saplings every few years, an abundance of lumber can be produced without disturbing the surrounding land. In nature, saplings produced in response to trauma will grow to form natural circles of mature trees, sometimes called “fairy rings”.
Kuma bamboo grass (Sasa veitchii), an evergreen, retains its broad foliage into winter. There are many species of bamboo growing around the Arboretum, all of which I’m sure are managed meticulously, as bamboo has a habit of spreading rapidly and persisting stubbornly.
The flaring base of the dawn redwood (Metasequoia glyptostroboides) is an impressive sight. Redwoods growing on the West Coast, in native humid conditions, reach incredible heights. While the species will survive in New England, its growth will be considerably restricted.
The bright red fruit of winterberry (Ilex verticillata) is a common sight in New England, especially around swamps and wetlands. It is prized as a ornamental species, and its boughs are harvested throughout the holiday season for use in traditional decoration.
The bark of this dragon’s claw willow (Salix babylonica “tortuosa”) is covered in what looks like burls. Burls are layered growths of tissue that form in response to damage caused by disease, insects, weather, etc. Typically, burlwood is full of dormant buds that can form suckers in response to stress. I’m not entirely sure what caused the bulbous formations on the tree here. With its fine, twisting branches and gnarled trunk, this tree has an ominous presence in the winter landscape.
A more benign sight is that of the striped maple (Acer pensylvanicum ‘erythrocladum’), with its bright, colorful striations.
The psychedelic winter buds of the Manchu striped maple (Acer tegmentosum) are something else. The banding on this twig represents the scars where leaf petioles and bud scales were attached in past seasons. Counting bud scale scars can sometimes be used to determine the age of a branch.
The foliage of this Fujiyama Rhododendron (Rhododendron brachycarpum) looks to be wilting, possibly from a lack of precipitation or the rapid changes in temperature. The Rhododendron genus is vast, and different species respond to winter conditions in different ways. Some experience color change, and some show no signs of change. On this plant, next season’s prominent flower buds can be seen clearly.
Magnolias buds are gorgeous, sporting a thick layer of protective hairs and colorful twigs. The buds of this anise leaf magnolia (Magnolia salicifolia) look delicate, but underneath their fur coats are thick, weatherproof layers. I recently learned that the protective organs surrounding these buds are not scales, but actually stipules–leaflike outgrowths that have evolved to serve a variety of purposes
The Chinese fringetree (Chionanthus retusus) produces delicate puffs of white flowers and bright blue berries. It is native to China and Korea and is prized as a ornamental species in North America.
The London planetree (Platanus x acerifolia) aka American sycamore is a common street tree planted throughout the northeast. Its characteristic mottled bark is able to rejuvenate and shear off, making it well suited to dealing with urban pollutants.
The fruit of the planetree forms a tight ball, which gradually comes apart to release fine, wispy seeds that are carried by wind and animal. I had a hard time finding this single fallen seed ball, although many had been retained on the tree.
I came across a millstone buried near a grove of beeches. Millstones are common artifacts in New England, relics from a bygone agricultural era. Today, they are used as lawn ornaments and architectural details. The snow on top had already melted, possibly as a result of the granite stone retaining more heat than the soil around it.
This bigcone dragon spruce (Picea asperata var. ponderosa) has a beautiful profile. I looked around for cones but couldn’t find any. In the foreground of this image, you can see piles of branches recently cut by the Arboretum groundskeepers. Winter is an excellent time for pruning, as trees enters dormancy and the majority of their energy has moved into trunks and root systems.
I found traces of maintenance all over the arboretum. The oriental cherry (Prunus serrulata ‘Washi-no-o”) shows a large cut where a major branch was removed some time ago. The wood has already begun to dry and contract. Eventually, growth from the cambium will wrap around the edges of the wound, sealing it off.
Specks of fungus can be seen growing on the cut surface of the cherry tree. At one time, horticultural knowledge dictated that wounds be covered with hydrophobic, tar-like substances to encourage rapid healing. Today, we know that such treatments can actually trap and incubate pathogens, causing rot. Healthy trees are more than capable of healing wounds naturally.
The unknown species in the bottom picture was cut all the way back, and will hopefully produce a flush of juvenile shoots come spring.
The fruit of this Soulard crab apple (Malus x soulardii) had been almost completely retained on its branches. Nearby, another crab apple had completely lost its fruit. I’m not sure of the exact cause of this phenomenon, but I’m sure it’s related to the different species used in these hybridizations.
This thicket of red twig dogwood (Cornus alba ‘Sibirica’) is a brilliant color. Cornus alba has recently become incredibly popular and can be seen in many front yards.
I found some nice-looking patterns in the ice near the dogwoods. It seems that the surface debris had a significant effect on the formation of the ice.
The paperbark maple (Acer griseum) is incredibly striking, and stands out in contrast to the surrounding maples. Its flaky, colorful bark gives it a glowing appearance.
I had initially planned on photographing the winter buds of the species that the Tree Spotters monitor throughout the year. Unfortunately, it was too cold, windy and dark to make many good bud images, so I ended up wandering for most of the afternoon. I did manage to photograph some branches against the gray sky.
One exception was this photo of a yellow buckeye (Aesculus flava) bud. I’m planning on visiting the Arb again soon, depending on the weather, so keep your eyes open for a bud-centric post!
Thanks for reading,
Here are more images from the day: