By Rob Paratley

Sycamore is certainly among the first trees that anyone learns to identify. People first notice its mottled bark that sluffs off, giving way to a creamy white appearance in the higher trunk and upper limbs. It is a common sight along stream courses, farmsteads, parks and city streets. Sycamore is native to eastern United States (and lowest Ontario Canada), ranging north to the upper Midwest, the north shores of Lakes Erie and Ontario, to southern New England. It ranges far into the South but doesn’t quite make it to the Gulf Coast. Sycamore follows the major river courses into the Plains states

Sycamore is a tree of wet soils, found naturally along streams of all sizes, as well as the margins of wetlands and in upland seeps. It is often seen clinging to a streambank with its roots exposed on the muddy bank. Unlike true swamp dwellers though, its roots cannot remain inundated indefinitely, tolerating up to about two weeks of flooding. Nevertheless, it is on the alluvial soils of the lower Ohio River and Mississippi, and other southern bottomlands, that sycamore attains its greatest size. Because sycamore is both fast-growing and potentially long-lived, trees 100 feet tall and 4 or 5  feet in diameter are not uncommon. Sycamores over 12 feet in diameter have been recorded! In the South it grows in floodplain forests with sweetgum, sugarberry, elms, pecan, green ash, silver maple, willow, and a number of bottomland oaks. In the upper Midwest, sycamore lines streams with American elm, red maple, black ash, and cottonwood. Also in the north, sycamore can be found in poorly drained mucky or even peat soils. In these situations it does not attain great size.

Sycamore’s Latin name is Platanus occidentalis. It has several additional common names in use in various parts of its range: buttonwood, buttonball tree, or, in comparison to the London planetree, American planetree. The London planetree looks very similar to our sycamore, and is in fact a hybrid with sycamore as one of the parent species (It is Platanus x acerifolia; the other parent is an East Asian species called Oriental planetree). North America has two other species of Platanus- one in California and one in Arizona. Both are found in cool shady canyons or along streams, like their eastern cousin.

The plant family containing all these is the Platanaceae. Although it is a very small family comprised of the single genus Platanus,  it has an interesting prehistory. Planetree fossil leaves and even fruit impressions are quite common in the fossil record from the later part of the Cretaceous Period, the last age of the dinosaurs, (100 million years ago) to the present. This makes its fossil record 10s of millions of years older than the maples, elms, oaks, and ashes that it associates with in our eastern forests. Recent DNA work has confirmed that the sycamore family is in fact an ancient one. But the patterns seen when researchers compare plant molecular “fingerprints” have provided some unexpected results. Before molecular tools were used in taxonomy, the sycamore family was thought to be related to a group of mostly wind-pollinated families containing sweetgum, elms, oaks, birches, and such. But in fact the sycamores are only very distantly related to these trees.  Its closest living relative family is the Southern hemisphere protea family (Proteaceae), common enough in Australia and South Africa, but only found in California and Florida gardens in North America. The proteas resemble our sycamore hardly at all. Many plant researchers are still scratching their heads over that connection. 

The reproductive pattern in sycamore is typical of bottomland trees, which often have a “weedy” life history. This means that the tree reaches reproductive maturity rather young, flowers profusely, and produces very numerous light & aerodynamic fruit. Sycamore produces compact balls of tiny, single-sex flowers. The males and the females are in separate parts of the same tree. Wind pollination is the rule. When fertilized, the females develop into a round cluster of very light 1-seeded achenes. The perianth of the flower (what in a plant with showy flowers might be the sepals & petals) is in sycamore highly modified into a cluster of hairs. This brush-like structure helps the light fruit catch the wind and potentially travel long distances, allowing  sycamore to colonize disturbances along stream courses.

The wood of sycamore is heavy and hard. This is somewhat atypical for a fast-growing floodplain tree. The wood is somewhat strong but difficult to work and can warp when seasoned. It has no odor and gives off no taste or stain. It has many uses. In the past, butcher blocks were almost exclusively made of sycamore wood, a testament to its durability and strength, and to its lack of odor or taste. Today, sycamore wood is used for furniture, veneer, interior finish, musical instruments, and also for lower end uses-  rail ties, posts, crates and boxes. Sycamore wood is prone to rapid decay. The heartwood of mature sycamores is very often rotted out. In pioneer times, settlers stored grain and smoked meat in these large hollowed-out trunks when sawn into convenient lengths. Many birds or mammals use these cavities for nesting and denning sites. Imagine pioneers in southern Ohio or Indiana taking shelter themselves in the  hollowed out trunk of a giant until the cabin could be built.  Settlers also stabled animals in them!  Other historical uses included the wide wooden panels in Pullman passenger train cars, taking advantage of the large girth of mature trees. Piano and organ cases were also made of sycamore wood. My favorite historical use was for wooden washing machines! Was there really such a thing? Apparently so, you can find pictures of early 20th Century wooden washers on the Internet.

Sycamore is also an important ornamental tree, although its cousin (and offspring) the London planetree is more frequently used. Both grow rapidly, and, once established, can thrive on a wide variety of soils. Best growth is on consistently moist soils. Typical of bottomland trees, sycamore is tolerant of the compacted heavy clay soil so common in urban and suburban areas. It is also somewhat tolerant of urban conditions like air pollution, although it is sensitive to ozone. London planetree is apparently even more tolerant of urban conditions. Sycamore needs a lot of space. An open grown tree can have a canopy spread of over 100 feet, even wider than it is tall. Although very handsome when fully grown and wide-spreading, sycamore is considered messy and high maintenance. It consistently drops branches, leaves, and fruit clusters. Another serious downside is the tree’s susceptibility to insect damage and disease. A leaf spot disease and a sycamore anthracnose (a fungus) take their toll, the latter creating much dieback and deformities like witches’ brooms (dense tangle of deformed branching).  Another fungus causes a trunk deformity called cankerstain. Sycamore is plagued by insect pests like the sycamore tussock moth, aphids, bagworms, and thrips. London planetree fairs somewhat better, but is also prone to cankerstain.  

Photography

1. Sycamore leaves (P. Griffin, Public Domain)
2. Two sycamore trees near Scovell Hall on University of Kentucky campus (N. Williamson)

About the Author

Rob Paratley is an Agriculture Research Specialist in the University of Kentucky Department of Forestry and Natural Resources. Rob has taught several courses at the University of Kentucky including Taxonomy of Vascular Plants, Economic Botany, and is the Curator of the UK Herbarium. Email Rob at rparatl@uky.edu.