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Sycamores are among the West’s most biologically useful trees. They line creek-cut canyons in the desert, extending a green and gracious welcome to the human traveler and to whole plant and animal communities with their shade and shelter and, not least of all, the holes in their trunks. 

It’s one of those oddities that work well: they’re prone to developing hollow spaces when a branch breaks or falls off, and many of those holes are nicely suited to house squirrels and woodpeckers and even fancier birds. They’re the favorite housing option of elegant trogons, for example.  

The elegant trogon (yes, “elegant” is part of the name; it used to be “coppery-tailed trogon”) is the northernmost relative of the resplendent (yes) quetzal, Central America’s nearly mythical emblem. Trogons get into southern Arizona, and those sycamore canyons are where to see them, and Cave Creek Canyon near Portal is the sycamore canyon to try first. It’s a birder’s haven, lively and inviting and full of hummingbirds and other treats. And trogons.  

We drove there years ago, looked in vain for trogons in the evening, and crawled into the tent when it got dark. At some ungodly hour of the morning, we jolted awake at the distinctive “Gowp gowp gowp” we’d been hoping for, shot sheet-clad out of the tent, and focused on that incredible blue, no, green, no, blue iridescent back and intense red belly, and another bird, a soft-brown and coral female, following closely from hole to hole in the trees above us. 

We were watching part of their courtship, in which the male takes the female around to every available tree hollow he can find and says, “This one? This one? How about this one?” until she decides on their home for the season.  

Unfortunately I’ve never heard a report of a trogon in Berkeley, in spite of our numerous sycamores. Maybe we have the wrong ones. Mostly what we have, like innumerable other cities, is Platanus X acerifolia (or Platanus X hispanica, depending on what book you’re consulting), called London plane. The species is from Spain, and was cultivated and crossbred there and in Oxford, so I guess it has some academic cachet too.  

This has become a wallpaper tree, ubiquitous and taken for granted; one guide calls it “more at home in city than in country environments.” It’s something of a plain Jane in this climate, as it doesn’t even manage to turn yellow in fall. It does have its virtues as a street tree, though: relatively well-behaved vis-à-vis sidewalks; tough about air pollution; tolerant of drought and water and assorted kinds of drainage. It has a handsome profile, and the bonus of good looks up close, with its platy, mottled bark. It’s adaptable to pruning, too, including stunt-pruning like pollarding. 

There are several double rows of pollarded planetrees on the UC campus, one right by Sather Gate. This poodle-ish practice had a practical origin, as a way to harvest firewood every year without killing trees. After early training to a strong profile, a tree is cut back every winter to the same few limbs, and in spring it sends out a spray of shoots from each of those. After a few years, those points become huge knobs, which give an interesting winter profile to the tree. It’s important not to cut behind those knobs—and to choose your species carefully, as this is a mutilation that not every tree can tolerate.  

Sycamores, including planetrees, are susceptible to anthracnose, a fungus infection that hits the leaves late in the year and makes them look gray and listless and nasty. Of course it sets the tree back a bit. It’s also allergenic, a big consideration when you’re planting lots of the same species in a small space with lots of humans. Fortunately, tree mavens have bred resistant cultivars, and those are being planted.  

Some of our tame sycamores demonstrate the virtue of having trees—any trees—in cities, as vertical habitat. When I’m working at the Ecology Center in winter (which is starting now in bird terms) I can always look out a window to the median strip on San Pablo and see yellow-rumped warblers darting around in the planetrees. 

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