Platanus occidentalis L.
by Scott VanHoveln
Other common names include: American planetree, buttonwood, American sycamore and buttonball-tree
Sycamore occurs abundantly along streams and bottomlands, but is also tolerant of drier sites. It is common to all states east of the great plains except Minnesota, extending from southwestern Maine west to New York, through southern Ontario, central Michigan, and southern Wisconsin; south in Iowa and eastern Nebraska to eastern Kansas, Oklahoma and south central Texas; east to northwestern Florida and southeastern Georgia. Sycamore is also found in the mountains of northeastern Mexico (Burns and Honkala, 1990).
Sycamore is tolerant of a wide range of climates with average annual temperatures ranging from 40 to 70 F with annual extremes between 105 and -30 F. Average annual precipitation generally ranges from 30 to 80 inches with between 100 and 300 frost free days per year. The natural occurrence of this species is most probably limited by frosts in the North and by dry climates in the West (Burns and Honkala, 1990).
Bottomlands and alluvial soils along streams are sycamore's preferred rooting sites. It is most common on Entisols, Inceptisols, and Alfisols, and occasionally found on Vertisols, Histosols, and Mollisols. Sycamore is tolerant of wet soil conditions but cannot withstand flooded conditions for prolonged periods. It grows on depressions having slow drainage, as well as on wet muck land, shallow peat soils, and those soils associated with river bottoms and flood plains. Generally, this species grows best on sandy loams or loams with and good supply of ground water that drops often enough to give sufficient drainage and aeration during the growing season (Burns and Honkala, 1990).
Production and Growth
Sycamore flowers appear from March to May. The tree is monoecious; the male flower clusters grow on short stalks on branchlets of the previous year and female flower clusters appear on the older branchlets. They have round, drooping heads with numerous, minute individual flowers. Male heads are yellowish green and female heads are rusty to dark red (Brown and Kirkman, 1990).
Fruit /Seed Production and Dissemination
The mature sycamore fruit is a round seedball about 1" in diameter, comprised of many closely packed achenes. The seed itself is long and narrow with a light brown, hairy, thin but hard seed coat. The fruits ripen and the wind disseminates the seeds (although water may carry them and deposit the seeds on mud flats where conditions are favorable for germination) in September and October, but they often remain on the tree over winter, falling off the following spring. Fruiting may occur as early as age 5, and continue for as many as 200 years, Good seed crops usually occur every other year with the seed count being approximately 200,000/lb. Late spring frosts commonly kill flowers, leaves and even twigs, reducing seed production (Burns and Honkala, 1990).
Yield and Rotation Length
Sycamore is a large, fast growing tree, often attaining heights of 100 feet or more. Diameters as large as 15 feet have been recorded. Height growth of 20 feet in ten years is common on some sites. Sycamore in a North Carolina stand had an average D.B.H. of more than 9" and an average height of 70'. Volume in this stand was 32.3 m3/ha of sawtimber and 75.6 m3/ha of pulpwood. At age 22 this stand is expected to have 140 m3/ha of sawtimber. Plantation growth potential seems to be greater than that of natural stands. In an eleven-year-old Georgia plantation, annual yield was 17.2 m3/ha while a 4 year coppice rotation in the Georgia Piedmont yielded from 24 to 32 m3/ha. These figures are slightly higher than average yield for typical southern mixed hardwood stands. In general, these stands were not managed to optimum intensity and are probably not indicative of maximum obtainable yield (Burns and Honkala, 1990).
Some tree improvement has been conducted on sycamore with resulting gains in early growth rate. Geographic variations in sycamore are pronounced, with trees of southern origin having faster growth than those of more northern origin when planted very near or even slightly north of their seed source (Burns and Honkala, 1990). It has been suggested that seeds be transported no more than 100 miles north of their origin (U.S.D.A.).
Seeds are generally sown without any pregermination treatments, resulting in a large percentage of sound seeds germinating. Germination is epigeal, and light-dependant. Under the necessary direct sunlight, sycamore seedlings develop strong, spreading root systems and can grow 36 to 48 inches in height the first year (Burns and Honkala, 1990).
Many insects feed on sycamore, but generally the only serious damage is done to ornamental or less vigourous trees. The more important insects are the sycamore lacebug, the flathead sycamore-heartwood borer, and the sycamore tussock moth. Other assorted leaf feeders, borers, beetles, moths, and caterpillars, as well as ants can also attack sycamore. Most diseases are not a problem in the nursery (Burns and Honkala, 1990).
International Forest Seed Company cites a cost for genetically improved sycamore seed as $150 per pound. Seedlings from Superior Trees Incorporated will cost $140 per 1,000.
One-year-old seedlings may be successfully used for reforestation or initial establishment. Direct seeding will fail on most sites due to level of moisture necessary to insure germination (U.S.D.A.). Coppice reproduction is very good in sycamore, especially in short-rotation pulpwood plantings harvested in March. Cuttings from young stems will work with the best groeth comming from those cut from near the root collar. Cuttings from mature trees require modified rooting methods (Burns and Honkala, 1990).
Wood Properties and Uses
Sycamore has a green specific gravity of 0.46 and a dry specific gravity of 0.49 (Haygreen and Boyer, 1989).
Haygreen and Boyer (1989) give the green and dry MOE of sycamore as 1.06 and 1.42, respectively. The MOR is 6,500 green and 10,000 dry.
With fast initial growth on a wide range of sites, sycamore is being used more and more for fiber (Burns and Honkala, 1990). It has relatively hard wood, hence its use as implement handles, boxes, meat cutting blocks, crates and woodenware. Sycamore is also used for veneer and particleboard (Brown and Kirkman, 1990).
Brown, Claud L. And L. Katherine Kirkman. 1990. Trees of Georgia and Adjacent States. Portland, Oregon: Timber Press.
Burns, Russell M. and Barbara H. Honkala. 1990. Silvics of North America Vol. 2. Forest Services, United States Department of Agriculture.
Haygreen, John G. and Jim. L. Bowyer. 1989. Forest Products and Wood Science: An Introduction. Ames, Iowa: Iowa State University.
-------------------------------. Trees for Reclamation: Platanus occidentalis. Forest Services, United States Department of Agriculture.