Appreciating and Conserving the Platanus — the Planetree or Sycamore
by Gerry Gilmartin
The American sycamore is North America’s largest native broadleaf tree. Sycamores belong to one of the planet’s oldest family of trees and can live 500 to 600 years. They have been planted extensively for centuries in the Hudson Valley as shade trees and for their decorative appearance. They are widely valued for their beneficial ecological impact, particularly in the urban environment. The London planetree, the hybridized cousin of the American sycamore, ranks as the tallest street tree in NYC, the oldest in Central Park, and the most common in Brooklyn.
Species include: Platanus occidentalis — American planetree or Sycamore, the largest of the Planetree family which can grow to more than feet tall with a similar spread; Platanus x acerifolia — London planetree; and Platanus orientalis — Oriental planetree.
Planetree leaves are large, coarse, and Maple tree-like, 4 to 10 inches long and wide, with sharp teeth on lobe edges and veins that meet near leaf base. The middle lobe of the American sycamore is broader than long, whereas the London plane leaves are often longer than broad.
Fruit grows in pendulous, ball-like clusters that ripen in the fall. The fruit of P. occidentalis occurs singly on the stem. That of P. x acerifolia is generally borne 2 or 3 together on a slender stem. The fruit of P. orientalis usually appears in clusters of 3 or more. The fruit head contains hundreds of tiny seeds with hairy tufts.
The outer bark is mottled and ranges in color from reddish, dark-brown or olive-green to creamy-colored. Trees grow so large that they continuously shed their bark. A distinguishing feature is the color of the inner bark after exfoliation. The American sycamore displays distinct, almost-white upper branches, and brown, scaly bark on the lower trunk. The inner bark of the London planetree is smoother and becomes a lighter brown, gray or olive-green with no scales, hence earning it the name of “army” or “camouflage” tree.
Planetrees prefer a rich, moist soil, but are very adaptable. They grow best in full sun. They are not particular about soil pH and will even withstand seasonal flooding, drought, and compacted soil conditions. They have been used extensively as street trees because of their tolerance of harsh conditions.
Trees enrich and improve the environment in many ways. They clean and cool the air, lower stormwater runoff, and conserve energy, in addition to raising property values, beautifying communities, and enhancing personal well-being. Their benefits are directly associated with tree size: the larger a tree, the more respiration and transpiration that occur because of the canopy cover and leaf surface area. These trees:
• Clean the air by absorbing carbon dioxide and gaseous pollutants in their woody tissue and by capturing particles such as dirt, dust and soot.
• Reduce energy generation and conserve natural resources by lowering air temperatures through transpiration and by providing shade, and by limiting heat loss from wind.
• Improve water quality by capturing rainwater on their leaves and branches and by absorbing contaminated stormwater runoff through their roots; and
• Provide food and shelter for wildlife.
(The above was excerpted from the conservation exhibit about platanaceae, trees of the Planetree family, for GCI’s 2010 Gilded Cage Flower Show.)