Sycamore, American Sycamore, or American Planetree

(Platanaceae - Planetree Family)

Form

• large shade tree
• maturing at about 80' tall by 60' wide under urban conditions, but much larger in the wild
• upright pyramidal to upright oval growth habit in youth, becoming upright irregular and spreading with age
• rapid growth rate

Culture

• full sun to partial sun
• prefers moist, deep, rich soils in full sun, but is very adaptable to a wide variety of soils, including dry soils, wet soils, compacted soils, poor soils, and soils of various pH
• propagated primarily by seeds, but also by rooted cuttings
• Planetree Family, with several minor disease and pest problems; however, anthracnose (Gnomonia veneta) is a serious disease that causes severe dieback of the emerging stems and foliage in afflicted trees in mid- to late-Spring, and a resulting "witches' broom" of subsequent whorled stems that emerge in early Summer
• low availability, in ball and burlap form (although Platanus x acerifolia, London Planetree, is abundantly available)
• Anthracnose (when present) often afflicts the same trees year after year, while other trees of the species may go relatively unscathed in most years; however, the disease is most devasting in Springs which are above average in rainfall, or in microclimates where air circulation is poor (such as in areas where surrounding trees are dense and/or the lower Sycamore branches are close to the ground)
• Sycamore is somewhat sensitive to being transplanted in Autumn, and care should be taken to amend the soil, fertilize, water thoroughly, mulch liberally, and avoid Winter salt spray, to enhance survival chances during the first Winter

Foliage

• green-gray to medium green, alternate, three- to five-lobed with incised margins, about 6" long and slightly wider, having a truncate base with a 4" long petiole, and with an overall shape that resembles a large Sugar Maple leaf
• leaves are pubescent on both the upper and lower surfaces when young (contributing to the grayish Spring color), but are only pubescent on the lower leaf veins by Summer (at which time the glabrous upper surface turns to a medium green color)
• the large, thick, wide foliage often flutters in the breeze, and turns an unnattractive brown-yellow to chartreuse color in Autumn

Flowers

• monoecious (separate male and female flowers on the same tree), in April with the emerging foliage, and ornamentally insignificant

Fruits

• usually occurring as a single fruit on a 3" long pendulous peduncle
• the round tan fruits occur as furry balls, with the "fur" attaching to each of many interior seeds for subsequent wind dispersal

Twigs

• gray-green, pubescent on first-year growth, and with alternating ovoid tan Winter buds
• stems from the terminal leader, branch tips, or watersprouts are straight and very fast-growing, while those from older branches grow at a medium rate and are often semi-pendulous and zig-zag
• large branches spread very wide with maturity and often arch downwards under their tremendous weight, and eventually become prone to lightning, wind, or ice storm damage over the long life of the tree

Trunk

• the white, cream, and olive-green interior bark is exposed on an annual basis as the tan-gray exterior bark exfoliates in rolled-up, tube-like sheets every mid-Summer
• the brown-gray lower trunk is composed of small blocks and plates, and is not ornamental as compared to the lightly-colored exfoliating upper trunk and spreading branches of the canopy
• mature specimens can reach 3' to 6' in trunk diameter
• in spite of its very large size, Sycamore rarely has basal trunk flare or surface roots, unless it is improperly sited in a restricted root zone (such as when used as a street tree) or some of its roots are exposed due to erosion (such as at a stream embankment)

ID Summary

• although American Sycamore (Platanus occidentalis) and London Planetree (Platanus x acerifolia) are often difficult to tell apart at first glance, the following features, especially in combination, can be used to differentiate between them:
  • London Planetree is now the preferred choice of nursery growers due to its relative Anthracnose resistance, and is found much more often in an urban site where it has obviously been intentionally transplanted
  • Sycamore is native to Eastern North America and is a predominate tree found along streams, rivers, bottomlands, and neglected wastelands, while London Planetree rarely escapes to the wild
  • London Planetree has relatively smooth bark, with an inner bark that is primarily olive green, while Sycamore has a bark that strongly exfoliates in mid-Summer to expose an interior bark that is a mottled combination of white, cream, green, and gray
  • London Planetree usually has its fruits borne as two per stalk, while Sycamore usually has its fruits borne as one per stalk
  • Sycamore is susceptible to leaf and stem Anthracnose in Spring, while London Planetree is prone to cankerstain (a fungal disease of the bark and cambium) and frost cracks (originating as fissures of the bark and cambium in Winter)
  • London Planetree is quite tolerant of poor soils and aerial pollution, whereas Sycamore prefers rich, deep, moist soils and no pollution
  • only London Planetree will develop many small knobs on its smooth trunk with maturity which are not associated with healed-over branch stubs, while both Sycamore and London Planetree may each have large knots on their trunks with maturity that represent sites of previous branch attachment

Function

• shade, specimen, or focal point tree in large open areas (it should not be used as a street tree, or as a shade tree for small lawns)

Texture

• bold texture in foliage and when bare
• average density in foliage and open density when bare

Assets

• rapid growth and establishment
• exfoliating ornamental bark on middle to upper trunk and branches
• bold texture, especially in Winter outline
• wet- or dry-site tolerant

Liabilities

• Anthracnose is a serious potential cosmetic disease, causing defoliation in Spring
• exfoliating bark litter in mid-Summer, and stem litter year-round
• storm damage that adds up over time for a very large tree
• poor fall color, with large leaves as leaf litter
• gets much too large for many urban sites

Habitat

• native to moist or wet bottomlands of the Eastern United States
• zones 4 to 9

SELECTIONS

Alternates

• trees with highly ornamental bark (Acer griseum, Betula nigra, Betula papyrifera, Carya ovata, Fagus sylvatica, Platanus x acerifolia, etc.)
• very large shade trees (Ailanthus altissima, Celtis occidentalis, Liriodendron tulipifera, Populus deltoides, Quercus macrocarpa, Quercus rubra, etc.)
• large trees for continuously moist to wet sites (Fraxinus pennsylvanica, Gleditsia triacanthos, Juglans nigra, Nyssa aquatica, Populus deltoides, Quercus palustris, Salix alba, Taxodium distichum, etc.)

Variants

• Platanus x acerifolia - London Planetree - a hybrid of Platanus orientalis X Platanus occidentalis, similar to American Sycamore in many morphological and cultural aspects, with the subtle differences noted above under "ID Summary"; however, London Planetree is abundantly available, and has been long propagated and transplanted for its supposed resistance to Anthracnose, especially the cultivar 'Bloodgood'

NOTES

Translation

• Platanus is the Greek name for Planetree.
• occidentalis refers to the Western Hemisphere origin of the American Sycamore.

Purpose

• Sycamore is a very large and spreading shade tree with showy white, cream, olive, and gray exfoliating bark, which is visible even when clothed in foliage due to the openess of its coarse branching habit.

Summary

• Platanus occidentalis is known as a massive shade tree that is native to bottomlands of the Eastern United States, having ornamental exfoliating bark in its middle and upper canopy, adaptability to wet or dry soils, and bold texture.