American Sycamore:
A Hospitable but Somewhat Lonely Tree

By Jane Hill

Sycamore Islander, February 2000

Sycamore Island's namesake, the American sycamore (Platanus occidentalis L.), is a tree of noble and ancient lineage. It is also big. On rich bottomlands, it can reach 150 feet in height and 12 feet in diameter. No eastern hardwood tops it, except the tulip tree, and none outdoes it in girth.

The most venerable sycamores encountered by the early settlers were 500 to 600 years old, with decayed, hollow interiors. Pioneers could stable a horse, cow, or pig in one, or shelter a whole family until the log cabin could be raised. Canoeists should know that a dugout canoe fashioned from sycamore by the early French in Illinois measured 65 feet long and, depending on which version of the story you believe, weighed or could carry 9,000 pounds.

The useful Sycamore.
Pioneers used hollow sycamore trees for shelter.
This small example grows a short walk above
the Island, near Lock 7, by the riverside.
The ancient giants are no more, but many of their descendants now exceed 100 years. The hollow interiors of these youngsters could hardly house a horse, let alone a human family (though see cover photo), but they make comfortable quarters for smaller animals, including raccoons, opossums, owls, and Wood Ducks. For years, a pair of Barred Owls has roosted in a cavity atop a sycamore along the C&O Canal in Cabin John. Sycamores are also hospitable to animals in other ways. A pair of Bald Eagles maintains a perennial nest in the crotch of a large sycamore near Great Falls, Maryland. Birders eye leafy sycamore canopies to catch glimpses of colorful warblers, orioles, and other songbirds that favor this species. In the northern and western parts of Maryland, Yellow-throated Warblers prefer tall sycamores for nesting.

Barred Owl sunbathes in Sycamore
crotch next to the canal (arrow).
Sycamores also host swimmers, who know that a massive trunk leaning out from the riverbank makes a perfect support for a rope swing: Climb out the trunk, grab the rope, swing out, and let go! The trunk's lean arises after repeated flooding scours away the soil around the tree base. The tenacious roots hold fast to the remaining soil, and the trunk, undercut on its river side, lists riverward. (The same happens to silver maples and willows.)

Sycamore foliage, like the trunk, is generously proportioned. The tree's genus name, Platanus, may come from the Greek platys, meaning broad, for the wide leaves. The species name, occidentalis, meaning western, is a designation that the famous eighteenth-century taxonomist Carolus Linnaeus, who named the tree, used more than once to distinguish North American plants from their European cousins -- in this

Eagle's nest above Great Falls.
case, from Platanus orientalis L., the Oriental plane tree. (The "L." at the end of the scientific names indicates that Linnaeus named them.) The common name sycamore is thought to be derived from the Greek words sykon, meaning fig, and moron, mulberry--probably in reference to sycamore's dangling fruits.

As good a host as sycamore is, its generosity does not extend to its flower or fruit structure. Its tiny blossoms are clustered in balls, both sexes on the same tree, male clusters separate from female. The meager blooms, which are dull in color and scentless, make no attempt to lure pollinators with nectar or flashy colors. Sycamore casts its pollen to the wind, and must produce plenty of it to ensure that some reaches female flowers on neighboring trees.

Many other eastern trees, including oaks, beech, walnut, birches, and elms, are also wind pollinated. Along with sycamore, they belong to an evolutionary line that arose from primitive, insect-pollinated flowering plants more than 100 million years ago, in areas that had alternating wet and dry seasons. In adapting to that climate, the trees became deciduous, shedding their leaves each dry season. During the leafless periods, the flowers were exposed to wind, and these species adopted wind pollination. These characteristics permitted the trees to venture out of the tropics, where flowering plants had originated, to drier, colder, temperate regions. There they were leafless during the cold season. Plants were sparse in these cool regions, and wind-pollinated ones quickly expanded their range and diversified, eventually dominating. But by about 80 million years ago, insect-pollinated plants also began to adapt to temperate climates. Their efficient exploitation of insect pollinators drove wind-pollinated plants into a decline in numbers and diversity. As insects and flowering plants continue to co-evolve, wind-pollinated trees may become even more restricted, yielding to plants with scented and showier blossoms, pollinated by insects. Thus, sycamore flowers may not be dressed for success over the long haul.

"Our" swing tree, a short walk, paddle,
or swim upstream from the Island.
An ominous sign is that sycamore has few living relatives. Platanus is the only genus in its family, Platanaceae, and there are only about eight species of Platanus worldwide. Botanists suspect that small, distinctive families such as Platanaceae and the other families of wind-pollinated flowering plants once had many more members and are now relicts.

The Potomac valley in winter reveals one of sycamore's more distinctive features: The bark on the upper trunks and branches is smooth and mottled, pale greenish-gray to yellowish or chalky white (some call it "camouflage" bark), in contrast to the drab grays of the other trees. Older bark of sycamore is dark, thick, and fissured. Stream valleys can be traced in winter by the zones of white-crowned sycamores lining them.

Sycamore fruits, clustered in balls that dangle from long stalks into the winter, are also distinctive, and, like the flowers, spare and dull colored. The tiny nutlets (technically, achenes), so tightly packed in the balls, cast their lot with the wind, like the pollen. They are not fleshy, like pawpaw or persimmon, which reward a hungry animal who takes the trouble to carry off a fruit and its contained seeds to new sites. Each sycamore nutlet has a fringe of brown, silky hairs at its base to help send the nutlet sailing on the breeze when the ball begins to break apart in late winter or spring.

White trunks stand out in winter, showing
the profusion of Sycamores in the bottom-land.
Palisade above Little Falls, looking from Virginia.
The wood of sycamore is unusual, too. With a beautiful figure of dark freckles in a cream to pink background, it intrigues woodworkers. It is hard, heavy, and fairly weak, and, with its interlocked grain, difficult to work, which limits its commercial value. Yet it has found its way into veneer, baskets, tobacco boxes, paneling, barrels, pallets, crates, butcher blocks, furniture, Pullman cars, and buttons (hence the old vernacular, buttonwood, for sycamore).

Appropriately enough, Sycamore Island's eponymous tree still grows abundantly there. Since the canoe club's founding in 1885, many of the island's trees have been allowed to grow, so some are even becoming venerable and hollowed out. Rocky, the island's resident raccoon, knew all about it.

Jane Hill, on the waiting list, especially enjoys swimming from the Island. She is a botanist and an accomplished birder, and for the last few years has been known as "The Voice of the Naturalist" for the Audubon Naturalist Society.