American sycamore (Platanus occidentalis)
Platanus occidentalis var. attenuata (Fern.) Sarg.
CONFIRMATION STATUS: Confirmed.
TAXONOMY: The currently accepted scientific name for sycamore is
Platanus occidentalis L. There are no accepted infrataxa. The London
plane tree (Platanus X acerifolia [Ait.] Willd.) is a hybrid of Oriental
plane (Platanus orientalis) and sycamore.
NATIVE STATUS: Native, United States and Canada.
GENERAL BOTANICAL CHARACTERISTICS: Sycamore is a native,
deciduous tree. Although not the tallest, it is amoung the tallest trees of
eastern deciduous forests. Mature heights range from 60 to 120 feet
(18-37 m). Reported diameters range from 2 to 6.6 feet (0.6-2 m). The
bark of young trunks has small scales. Bark at the base of large trunks is
deeply furrowed and up to 3 inches thick (7.6 cm); on the upper portions
of the trunk the bark exfoliates in patches, leaving areas of inner bark
exposed. The leaves are 4 to 10 inches (10-25.4 cm) long, often as broad
or broader than they are long. Sycamores form widespread, strongly
branched root systems. The fruit is a plumed achene; numerous fruits are
tightly aggregated into a ball-shaped fruiting head 0.8 to 2 inches (2-5 cm)
in diameter. Sycamore is characterized by rapid growth throughout its life;
it is also long lived (over 250 years). A sycamore measuring 140 feet (43 m)
tall and 120 inches (305 cm) dbh has been reported; a specimen from
Indiana was reported as 168 feet (51 m) tall and 33 feet (10 m) in circum-
ference. Open-grown individuals can achieve a crown spread of 100
feet (30 m) or more. A survey of big trees in seven mid-southern states
reported that the second and fourth largest trees (of all species) were
sycamores. The largest sycamore in these states was a Tennessee tree
140 feet tall (42.67 m) and 65.9 inches (167.4 cm) dbh, with a circum-
ference of 207 inches (525.8 cm), the largest circumference of any
tree in these states.
REGENERATION PROCESSES: Sycamore is monoecious. Plantation
-grown sycamores are usually sexually mature in 6 to 7 years. Natural
stands of sycamore usually produce appreciable numbers of seed at
approximately 25 years; optimum seed production occurs from 50 to
200 years of age. Seed production is not dependable from trees over 250
years old. Good seed crops are produced every 1 to 2 years. Sycamore
seeds are dispersed by wind and water. They have a relatively rapid rate
of descent for light seeds; the estimated lateral travel distance in a 6 mile
per hour (10 km/hr) breeze is 223.7 feet (62.8 m). Since seed dispersal
occurs at a time of year when water levels are declining after spring floods,
water dispersal often results in seed deposition on muddy flats that are
highly conducive to germination. They do require very moist conditions for
good germination and are tolerant of inundation. Soaking seeds in water for
up to 32 days did not reduce germination rates; the seeds did not germinate
during the soaking period. Sycamore seeds germinated at a significantly
higher percentage in light than in dark; they do not germinate well in heavy
litter or in deep shade. Sycamore seeds did not germinate in laboratory
tests at temperatures lower than 59 degrees Fahrenheit (15 deg C); they
germinated well at temperatures between 59 and 86 degrees Fahrenheit
(15-30 deg C), with maximum emergence at 68 degrees Fahrenheit (20
deg C) in the wetter part of a moisture gradient. Sycamore seedlings
require direct sunlight for good growth and establishment. At the end of
their first year, sycamore seedlings on clay soil showed better height
growth in partial shade than in full sun. On alluvial soil or loess, height
growth was better in full sun. Seedling roots penetrate the soil quickly
and grow deeper in loess soils than in alluvial or clay soils. Young syca-
more stems sprout readily from the stump. Sycamore can be vegetatively
propagated by cuttings.
SITE CHARACTERISTICS: Sycamore is primarily a species of alluvial
soils along streams and in bottomlands, but occurs occasionally as a pioneer
on drier upland slopes . It occurs on a wide variety of soils, including both
sands and clays. Its best growth occurs on sandy loams or loams with a good
supply of ground water but it also occurs on wet muck, shallow peat and
other, more poorly drained bottomland soils. Sycamore occurs on a variety
of wet sites, including shallow swamps, sloughs, and very wet riverbottoms
where soil is saturated 2 to 4 months during the growing season. Sycamore
seedlings survived almost 2 months of continuously waterlogged soils.
Sycamore is more tolerant of poorly drained soils in the northern parts
of its range. Sycamore is rated as moderately tolerant of flooding. In the
Northeast, sycamore occurs on sites with greater than 98 percent
probability of flooding in any given year. Sycamore is intolerant of flooding
during the growing season and will die if the entire tree is inundated for
more than 2 weeks. Saplings may be more resilient than mature trees due
to their higher sprouting capacity. Seedlings are less tolerant of flooding
than larger plants simply because they are more likely to be completely
covered by water during active growth.
The elevational range of sycamore extends from sea level to 1,000 feet
(305 m) in the northern parts of its range and to 2,500 feet (762 m) in
the southern Appalachians.
SUCCESSIONAL STATUS: Sycamore is intolerant of shade. Seedling
growth is greatly reduced in deep shade (defined as 5 percent of full
sunlight). Sycamore occurs in forest types that are pioneer, transitional,
subclimax, and climax. Sycamore will pioneer on sand and gravel bars and
other newly formed land, often persisting through later seres, such as
sugar maple (Acer saccharum) - bitternut hickory (Carya cordiformis),
particularly on wet sites. It is an occasional pioneer on upland oldfield
sites, particularly in the central parts of its range. In Illinois, sycamore
was the most common tree species present as seedlings in local old fields.
In southern Illinois, 1- to 5-year-old sycamore seedlings were most
common on newly formed land, then on old fields, in cottonwood-willow
communities, and in soft mixed-hardwoods (elms, ashes, birches (Betula
spp.), silver maple, and red maple (Acer rubrum)); there were no
seedlings present in hard mixed-hardwood communities (oaks and
hickories). Sycamore usually replaces willows (Salix spp.) and eastern
cottonwood (Populus deltoides). The sycamore-sweetgum - American
elm type usually succeeds cottonwood on river fronts, but may pioneer
on heavily cutove sites or old fields in bottomlands. This type may persist
as a subclimax type where repeated disturbances such as flooding occur.
It is usually succeeded by swamp chestnut oak (Quercus michauxii) -
cherrybark oak or sweetgum- willow oak (Liquidambar styraciflua -
Quercus phellos). In the North Carolina Piedmont, sycamore and river birch
(Betula nigra) usually replace alders (Alnus spp.) and willows on small
islands or spits in streams after the land becomes stable and moderately
well drained. Sycamore and river birch are usually followed by elms
(Ulmus spp.), ash (Fraxinus spp.) and red maple. The presence of
sycamore in upland climax forests may be a function of disturbance
rather than a function of moisture or drainage regime; its establishment
in these woods may require larger disturbances than those produced by
single or multiple tree falls.
SEASONAL DEVELOPMENT: Sycamore flowers appear in May in
the northern parts of its range, and as early as late March in the South.
Late spring frosts will kill flowers, leaves, and twigs. The fruits ripen
from September to October or November, and usually remain on the tree
over winter, breaking up or falling off the following spring from February
GENERAL DISTRIBUTION: The range of sycamore extends from
southwestern Maine west to extreme southern Ontario, southern Wisconsin,
Iowa, and extreme eastern Nebraska; south to south-central Texas; and
east to northwestern Florida and southeastern Georgia. It also occurs in
the mountains of northeastern Mexico. Sycamore has become naturalized
to some extent from plantations outside of its native range, chiefly in
southern Maine, southern Michigan, southern Minnesota, and eastern
and southern Iowa.
SKY MEADOWS DISTRIBUTION:
Tree specimens can be found on trails marked in red.
Appalachian Trail/Old Trail
South Ridge/North Ridge
Rolling Meadows/ Lost Mountain
HABITAT TYPES AND PLANT COMMUNITIES: Sycamore is
found in quantity only in bottomland forests, particularly of elm-ash -
cottonwood (Ulmus spp. - Fraxinus spp.-Populus deltoides) types,
and cottonwood-willow (Salix spp.) types. It usually occurs singly or
in small groups. Sycamore is found occasionally along intermittent
streams within upland stands of oak-hickory (Quercus spp. - Carya
spp.) communities. It is a major pioneer species in the floodplains of
large rivers. In the Southeast pure stands of 40 to 100 acres (16-40 ha)
are sometimes formed; it rarely forms extensive pure stands in the
northern parts of its range. In the northern states sycamore is rarely
the dominant species; it increases (replacing silver maple (Acer
saccharinum)) with decreasing latitude.
IMPORTANCE AND USES: Sycamore does not provide much food
for wildlife, although the seeds are eaten by some birds including the
purple finch, goldfinch, chickadees, and dark-eyed junco, and by musk-
rat, beaver, and squirrels. Sycamore is rated as medium in suitability for
waterfowl habitat and low in suitability as deer or turkey food. Overall
sycamore is rated only fair for wildlife use. As sycamores age, they may
develop hollow trunks which provide shelter for a number of wildlife
species; some large, old individuals have formed cavities large enough to
be used as dens by black bear. Cavity nesting birds include the barred owl,
eastern screech-owl, great crested flycatcher, and chimney swift. Wood
duck use sycamores as nest trees.
The bottomland forests in which sycamore occurs are very important
wildlife habitat, sheltering numerous animal species including wood duck,
other waterfowl, upland game birds, and deer. In Indiana, riparian forests
in which sycamore occurs are important habitat for the endangered Indiana
bat, which uses these areas for nursery colonies.
Sycamore occurs naturally on disturbed sites if there is sufficient moisture
for seedling establishment. It occasionally occurs in mostly pure, well-
stocked stands on naturally regenerated strip-mined lands in the central
states. In addition, sycamore is often found in pure stands or in mixtures
with other hardwoods that pioneer on spoil banks, in waterway disposal
sites and in channelization projects. Sycamore saplings have also been
observed in small numbers on unreclaimed limestone quarries. Sycamore
is recommended for planting on all types of strip-mined land in many
northeastern and central states and in Florida, sycamore was planted on
a phosphate mine site for a wetland reclamation project.
Sycamore is a valuable timber tree; its wood is hard, with a twisted and
coarse grain, but not very strong. It is used for furniture, interior trim,
boxes, pulpwood, and particle and fiber board.
Sycamore is planted as a street tree, although it is highly susceptible to
ozone damage and is susceptible to foliar injury and reduced growth
when exposed to salt spray. The London plane tree is more resistant
to air pollutants and is more commonly planted as a street tree.
Crooked Run Valley