American Sycamore

I have been interested in trees for quite awhile now. I remember buying a copy of Audubon’s Guide to Trees in North America before I really delved into bird photography and identification. I have since lost that guide and got a better one, and am excited about getting back into figuring out what is what. This is a good first tree to learn in this series, since it is now one that I see everyday. It has begun dropping a lot of leaves already, but I am proud to have one of the largest American hardwoods literally in my backyard.

What is it? American Sycamore

What do the nerds call it? Platanus occidentalis

Who is it related to? It is in Platanaceae, or the plane-tree family, which typically have large scaly trunks and lobed deciduous leaves that broadly resemble the iconic maple leaf. The American Sycamore is the only native plane tree in Eastern North America, with the rest found all over the world. A similar looking hybrid, the London plane tree is planted in cities due to its resistance to pollution, and are often heavily pruned to make their canopies high and shady. Of similar name (but in different families all together) there is a tree called sycamore maple here in the US (and just sycamore in Europe), as well as other species called sycomore, of biblical fame.

How can you tell it is what it is? The most identifiable characteristic is the peeling bark. At the very base of the tree, the bark looks more or less like you would expect some other deciduous trees to look – a grey brown that is more on the scaly side. This particular species, however, is extra scaly, and as you go up the tree, the more scaly it gets. It gradually will get lighter and lighter, revealing more and more of the lighter colored underbark. This scalyness is shared with a very similar tree, the London plane tree, which is a hybridization of the American sycamore and a tree called the Old World sycamore. The main difference is that the London plane often has its peeling bark go down to the base of the tree instead of being a graduation from more solid bark, as well as usually having two flowers/seed pods to a stem, while the American sycamore has one.

The leaves are broadly maple-shaped, though they have a rounder appearance, with each lobe being less jagged and deep than the typical sugar maple shape. The seed pods, sometimes called sycamore balls, are golf ball sized sized pod that is spiky and is produced in the winter, falling in the spring.

Discussion: This tree first appeared on my radar last summer as a host tree for nesting eastern kingbirds and orchard orioles, which we learned about on a nesting course run by Leonard Weber of Eliza Howell Nature Walks. Barred owls and screech owls have also been known to make use of any hollow cavities. The largest cavities can support black bears as well, though what an experience that would be if one started living in our backyard here in metro Detroit.

These large cavities supposedly housed old-timey colonizers for a night or two in their travels (the largest found American sycamore is 15 feet in diameter, located in Ohio). In current times, their wood is most famously used as butcher block material, as its resistance to splitting make it suited for end-grain-up chopping. American sycamores can also be tapped for sap to make syrup like you could with a sugar maple, however it does not produce nearly as much sap and it is a bit harder to extract, often needing a vacuum pump.

The peeling bark is a unique phenomenon that is not well understood by scientists. Basically, it is too brittle to stretch to accommodate the fast-growing trunk and branches underneath it, eventually flaking off pretty much year-round. Why this developed evolution-wise is pretty much anyone’s guess. Some speculate it is to keep fungi and blighting insects out, or perhaps that a rock-solid bark is not needed to keep moisture in due to its naturally wet environment. A very convincing theory is that when the bark flakes off, the white underbark is now allows the trunk and branches to photosynthesize even when there are no leaves on the tree, which could also contribute to its speedy growth.