ETSU Arboretum
Tree of the Week
Sycamore
(Platanus occidentalis)
Our
native Sycamore is a common yet distinctive sight in both natural and
planted landscapes. It's bark— a “camouflage” pattern
of peeling patches, like tan, gray and brown puzzle pieces—eventually
turns to a smooth white on the mature trunk and branches. Sycamores often
grow in the sandy soils along streams and rivers. They can grow into massive
trees, with towering white trunks visible from afar, and stand out brightly
in the leafless winter landscape. Sycamores hold the record for the broadest
trunk of a native tree: over ten feet in diameter at four feet above the
ground. Along riversides one may see old trees with hollow trunks, caused
by canker and wood-decaying organisms, providing animal dens or playhouses.
Sycamores grow quickly and can live for hundreds of years. They bear large,
stiff leaves resembling maples in shape, and make excellent shade trees
for urban settings.
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| Medium
sized Sycamore tree in spring, growing in parking lot near ETSU
Public Safety Office and University Parkway. |
Sycamore growing in parking lot on a winter's morning with full moon. |
The
American Sycamore is native to the eastern and central United States,
occurring in all states east of the great plains except for Minnesota,
and also in the mountains of northeastern Mexico. It’s botanical
name, Platanus occidentalis, derives from “platy,”
Greek for broad, and “occidere,” Latin for “to set,
as in the sun,” meaning of the west. An old world species, Platanus
orientalis (orientalis, Latin for “rising” or of the
east), occurs from Asia Minor to the Himalayas. Hybrids between these
two species are known as the London Plane Tree, (Platanus x. acerifolia
or Platanus. x hispanica). These hybrids are the most common
street tree in major European cities like Amsterdam, Barcelona, Paris,
and Hamburg. The London Plane tree is highly tolerant of urban pollution,
can be cut back or coppiced repeatedly, and provides good shade for city
streets and sidewalks.
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A
common name for our native Sycamore is Buttonwood tree, referring to the
fruits, which grow in one-inch balls hanging from stringy three to six
inch stalks. The seed balls hang on the Sycamore all winter, then fall
apart in early spring to disperse their many small seeds, leaving a hard,
button-like core where the seeds were attached. Tufts of hairs on each
seed act as parachutes, scattering seeds widely. The seeds are also eaten
by birds and carried by water. The seed ball developed from the head of
female flowers which formed in the previous year. Male flowers are also
grouped in heads or spheres. Both male and female flower clusters occur
on a the same individual, so the tree is “monoecious.” Look
for these inconspicuous inflorescences in mid-spring. The American Sycamore
bears its seed balls singly on each stringy stalk. The oriental plane
tree produces three or more seed balls on each hanging stalk. The hybrid
London Plane tree typically bears two to three balls per stalk.
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There
are seventeen American Sycamore trees growing on the ETSU campus. A group
of fairly mature Sycamore trees grows along Gilbreath Drive between Gilbreath
Hall and the University School. The line of newly planted Sycamores or
London Plane trees is planted in front of the new Center for Physical
Activities. Tall Sycamore trees can be seen growing alongside the duck
pond at the Veterans Administration Mountain Home campus. In winter it
is very easy to spot native Sycamores at a distance or from the car window,
growing along streams and in bottomlands. The ETSU Arboretum has one young
specimen of the oriental plane tree Platanus orientalis, planted in 2003
on the north side of Gilbreath Hall.
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Sycamore trees can be bought from some local nurseries, such as Evergreen of Johnson City, which sells five foot trees in five gallon pots for about $40. They are occasionally available from outlets like Lowe's and Home Depot. Because our native sycamore is susceptible to leaf blight from spring anthracnose disease, tree experts recommend growing resistant hybrid cultivars such as ‘Columbia’ or ‘Bloodgood.’ A specimen of the attractive variety ‘Columbia,’ selected by the National Arboretum, is planted at ETSU just northeast of Gilbreath Hall. The cultivars mentioned above are available from mail-order nurseries such as Forest Farm (www.forestfarm.com) , for about $15 to $50 in one and five gallon pots.
While sycamores make magnificent, fast-growing shade trees, a couple down-sides warrant note. The large leaves make for autumn raking work. Also, the fuzzy brown stellate (star-like) hairs on the young leaves and stems can be irritating to the skin and eyes, especially in late spring when this pubescence is shed from the leaves.
Recommended Web Links for Platanus occidentalis:
USDA Silvics Fact Sheet, Platanus occidentalis (Sycamore)
Floridata, an internet plant encyclopedia, Platanus occidentalis entry
Additional photos of Sycamore tree, bark, leaves, and fruit can be found on the web site of Steven J. Baskauf.
Google Images of Platanus occidentalis
See past Trees of the Week
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ETSU Arboretum
Department of Biological Sciences
Box 70703
East Tennessee State University
Johnson City TN 37614Tim McDowell
(423) 439-8635
email: mcdowelt@mail.etsu.edu
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