Description and habitat

American Sycamore (Platanus occidentalis) is a large deciduous tree in the Sycamore (Platanaceae) Family, reaching up to 40 m tall at maturity, forming a broad, spreading crown. Old American sycamores often have massive thick trunks, often >1 m in diameter. The term “Sycamore” refers to a very wide variety of trees worldwide, including the Sycamore Maple (Acer pseudoplatanus), the Sycamore Fig (Ficus sycomorus), and several other trees worldwide. The other common name for the Ontario’s native Sycamore is American Planetree. It is also known as a Buttonball Tree. There are around 13 species of Sycamores in the world. The centre of diversity is found Mexico, with only a few species in Eurasia, most notably the Oriental Planetree (Platanus orientalis).

The leaves of Sycamore are 10-30 cm long, with an equal or greater width, making them among the largest tree leaves in Ontario. Planetrees have alternately arranged, palmately lobed leaves. These leaves are light green, with toothed leaf margins. They usually emerge later than other hardwoods, at the end of May. Autumn foliage is yellow or rusty brown, like elms (Ulmus. sp), giving the tree a more subtle appearance compared to the showier displays of other hardwoods such as maples and ashes. Sycamore bark is comprised of horizontally peeling plates, which expose the multicoloured inner bark. It can be various shades of brown, green, grey, brown, orange, or beige. Very old Sycamore bark is sometimes comprised of grey, squarish ridges divided by narrow. Flowers appear in late spring, with the fruit ripening in September.

Across North America, Sycamore has a large distribution. It found from Ontario’s Lake Erie Region west to Iowa, south to Texas and Florida. Throughout it’s range, it is by far the most common in bottomlands, riparian areas, and floodplains, rarely found as an upland tree in Ontario except when planted. However, Sycamore can establish in old fields on uplands, but is usually outcompeted by shade-tolerant mesophytic hardwoods later in the forest succession process. In it’s preferred riparian habitat, it does persist as a component of old-growth forests due to it’s tolerant of wet sites and long lifespan in ideal growth conditions. Common associates with Sycamore in bottomland environments include Black Walnut (Juglans nigra), Cottonwood (Populus deltoides), Hackberry (Celtis occidentalis), White Elm (Ulmus americana), and Bur Oak (Quercus macrocarpa). Along larger watercourses, it is abundant directly along riverbanks, usually with Cottonwood and sometimes Black Willow (Salix nigra). It is occasionally found in swamps, alongside Silver Maple (Acer saccharinum), White Elm, and ashes (Fraxinus sp.). The understory of Sycamore forests typically consists of flood-tolerant shrubs, ferns, and wildflowers.

Wildlife importance

As large Sycamore trees age, the heartwood often decays, providing cavities to a wide variety of species, especially small mammals and birds. The branches often provide nesting habitat for many riparian bird species. The seeds are consumed by wildlife, serving as a valuable winter food source when other options are scarce. Sycamore serves as a valuable tree for erosion control, stabilizes floodplains and riverbanks. The foliage is an important food source for some insect species, including the Sycamore Tussock Moth (Halysidota harrisii), Drab Prominent Moth (Fentonia ocypete), and Sycamore Lace Bug (Corythucha ciliata), the latter being a common pest species, though it provides a valuable food source to other species of wildlife.

Fun facts

• American Sycamore is commonly referred to as the largest deciduous tree in Eastern North America, in trunk diameter (though Tuliptree, Liriodendron tulipifera, is the tallest)
• Some sycamore seeds actually went to the moon in 1971, as part of the Apollo 14 mission! These seeds were returned to Earth, sprouted, and subsequently planted in many locations across North America.
• Sycamores are quite resilient trees, tolerant of air pollution, compacted soils, and wet conditions. This species and London Plane, the popular natural hybrid with Oriental Sycamore, are popular choices for urban planting. 
• Due to the peeling bark, some Sycamore trees appear as “white trees” in the winter, making them especially aesthetic in both natural and manicured landscapes

 

Written by Matthew Palarchio, HBSc in Environmental Sciences, Western University

Photos L-R:
Growth form © Matthew Palarchio
Bark © Matthew Palarchio
Leaves – Stock Photo retrieved from Canva
Winter tree © Matthew Palarchio

 

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