Platanus occidentalis Seeds | American Sycamore

Patchwork peeling bark in cream and olive on the trunk of an American sycamore — American Sycamore (*Platanus occidentalis*): Platanaceae, river banks and flood plains of eastern North America.

LATIN NAME: Platanus occidentalis

COMMON NAME: American Sycamore

Plant Profile

American sycamore is the tree that lines the creeks of the eastern United States, and it is recognised long before it is identified. The trunk is the giveaway: bark that peels away in irregular plates, leaving a patchwork of cream, olive, grey and tan, so that a mature tree looks as though it has been whitewashed and then rained on for a century. The leaves are broad, three- to five-lobed and maple-like, but they are alternate on the stem, which separates the tree from any maple at a glance. Fruit hangs in round balls on long stalks through the winter and breaks up in spring into a fluffy mass of seed. It grows fast and large, thirty to forty metres in the bottomlands, with a massive spreading crown and a trunk that can hollow out while the tree is still alive and bearing. It is a river tree, and it wants water.

Science & Biotechnology

Platanus occidentalis is a diploid, 2n = 42, and it hybridises readily with the oriental plane, P. orientalis, to give the London plane, P. x acerifolia, which is the tree of city squares in Europe. The three are separated by small characters: the American species usually has a single fruit ball per stalk, the oriental two to six, and the London plane two to three with a deeper leaf sinus. The peeling bark is a structural adaptation: the outer layers are shed as the trunk expands, which removes epiphytes and may reduce the load of moss and lichen in humid bottomlands. The species is hit hard by anthracnose, Apiognomonia veneta, which browns the young leaves in wet springs and can defoliate a tree in a bad year, though it rarely kills an established one. Seed is small and light, dispersed by wind and water along flood lines.

Uses & Benefits

The timber is heavy, hard and difficult to work, and it is used for butcher’s blocks, furniture frames, flooring and veneer, but it is not a major commercial species because the logs are often hollow. Its great value is in shade and stabilisation: it holds riverbanks, tolerates periodic flooding and grows fast enough to be a quick canopy. In the garden it is a large tree for a wet corner or a pond edge, planted for the bark and the winter fruit, and it is worth growing only where there is room. It is also a pollen source in spring and a host for the sycamore tussock moth. The name is a trap for English readers: in Britain sycamore means Acer pseudoplatanus, a maple, and the American tree is a plane.

Growing from Seed

Sow seed in autumn, either fresh into a seedbed or after three months of cold, moist stratification at 4 degrees; germination is often staggered over two springs, so do not throw the tray away. Surface-sow into a loose mix, cover lightly, and keep moist in bright light. The seedlings are fast and large, and they transplant well when young because the root system is fibrous rather than taprooted. Pot on or line out in the first year, and plant out at sixty centimetres to a metre in autumn, in deep, moist soil in full sun. Water through the first two summers, and give it space: the crown will eventually be twenty metres across. It tolerates hard pruning and pollarding, which is how it has been kept to size in parks.

Our Take

A fast, big river tree for wet ground, grown for the patchwork bark and the winter balls. Plant it only where there is room for a thirty-metre crown.

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