Photo by urbpan. This mulberry tree, growing in the parking lot of the Brookline Water and Sewer Division, had its entire top cut off, and has produced new, bush-like foliage.
Urban species #311: White mulberry Morus alba
When I was teaching myself to identify all the weeds and trees that were growing in my Brighton, Massachusetts yard, years ago, I nearly drove myself crazy with this one. My tree field guide was organized by leaf shape--whether the leaf was toothed around its margin, or lobed, or simple, round or long. This one tree had leaves that were simple (more or less round) or were mitten-shaped (asymmetrically lobed) or were sort of oak leaf like (symmetrically lobed all around); I didn't know where to begin. This was one of the many times that a field guide to urban species would have been helpful. As it turned out, that field guide concentrated on native species anyway, so trees from Eurasia were either not covered or marginalized, even though in North American cities they make up a huge percentage of the tree population. When, in summer, the tree produced copious amounts of fruit, drupes shaped like blackberries, it became clear what the tree was.
White mulberry is exceedingly common in many cities. It was introduced from east Asianin order to feed silkworms, for a silk industry that never got off the ground. Once it was established, birds were happy to gobble up the fruit and spread the seeds all over the New World. The berries are edible for humans, though you may have to sample the fruit of many individuals before you find some that aren't basically flavorless. The color of the fruit also varies from tree to tree. Some individuals produce fruit that is white, and never darkens to a more enticing color. Others bear fruit that is white, red, and nearly black, all at the same time. Red mulberry (M. rubra) is native to the northeast of North America, and may account for some of the better-tasting urban mulberries. All species of mulberry hybridize readily, and produce fertile offspring, so it may be difficult to ascertain whether a given tree is a pure white or some kind of hybrid.
White mulberry is an uncommonly hardy tree, enjoying many urban locations. Frequently it grows from bird droppings along a fence line or in a sidewalk crack. Like Ailanthus, it appears to be a simple weed at first, and then quickly develops in to a difficult-to-remove tree. It may develop as a shrub, or as a small, apple-sized tree. Many kinds of butterfly and moth larvae will fed on mulberry leaves, and they are a favorite staple of hobbyists raising silkworms and other caterpillars.
Mulberry in fall colors, at the Longwood trolley stop in Brookline.
Summer mulberry leaves at the shore of Leverett pond.
I would appreciate it if a reader would post a photo of the berries in the comments--can you believe that I didn't get a picture of mulberry fruit this year?