Sycamores in Winter

The American Sycamore trees in Eliza Howell Park may not be very evident during the summer months or in the fall color season, but they stand out from November to April, when most deciduous trees are leafless.

In old growth North American forests, sycamores grew massive trunks, up to 10 feet or more in diameter at times, perhaps the largest trunks of any native hardwood tree. These trunks, often hollow, were used by Chimney Swifts for nesting and roosting before large chimneys were built – and large trees were cut down.

Sycamores thrive in moist woods and near rivers, which makes Eliza Howell Park a great location for them. The sycamores in the park are not old growth, of course, and are no larger than other trees. It is the bark of the branches, not the size of the trunk, that calls attention to the sycamore in winter. The upper part of the tree often appears nearly white.

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The sycamores are not the most common tree in park but are scattered, both in the woods and in the open area. As with other trees, in the open, when they do not have to stretch high to get sunlight in the woods, their branches spread more. Note that the trunk close to the ground does not look noticeably more white than most other species.

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Sycamores are sometime used as shade trees in yards and along streets and this winter a neighbor called my attention to a fascinating phenomenon. One street in our Detroit neighborhood is lined with sycamores on both sides for several blocks. In the very cold spell in early January, many of them had large vertical splits in the trunk, often more than six feet long.

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Based on a little research, I think these are “frost cracks.” They occur, usually on the sunny side of the tree (south, or southwest) in very cold sunny weather, on thin-barked trees like sycamore.

The cracks normally close over as the weather gets a little warmer and are not fatal to the tree, though they may re-open in other winters and they leave a callous over the crack.

The next picture is of the same tree as above and was taken in the middle of February, exactly one month after the picture above.

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I had never seen such a frost crack in the sycamores in Eliza Howell, but after viewing the neighborhood trees, I went back and took another look. Not a single one that I checked in the park showed any evidence of such cracks, this year or in the past. This one is typical of the sunny side Eliza Howell sycamores.

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So what is the explanation? Why are the street-lining sycamores more susceptible to frost cracks than those in the park? I don’t know. But I do have an initial hypothesis. Trees planted in the narrow berm between street and sidewalk are not in as healthy of a growing environment – drier and with more rapid changes in temperature – as those in a woods or park. They are more susceptible because of these stresses.

That’s my working hypothesis until I learn more. What I do know is that I continue to enjoy viewing the sycamores in Eliza Howell Park even this late in winter, when I am looking for early spring birds.

3 thoughts on “Sycamores in Winter

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