This piece on galls was published quite some time ago, but it seems timely especially now, since I keep seeing galls!
Have you ever noticed, among the nuts the squirrels have left behind on the lawn, small, peach-colored, fuzzy balls? How about pocked-looking, speckled spheres at the foot of the oak tree out in front? If you look, you’ll see many other assorted shapes and sizes, hanging off trees, clinging to leaves, scattered along the curb. Galls are everywhere, but most people know little about them.
Galls are growths formed by the reaction of a plant to mechanical irritations or chemicals produced by insects, bacteria, fungi, and viruses. Insect larvae live inside the protective shells of insect galls, growing to adulthood over the winter before emerging to the outside. Insect galls are generally more benign than the other varieties, some of which can cause ugly and sickly results for the plant.
There are more than 1500 types of insects in the United States that form galls. Wayne’s Word, an online natural history textbook by biology and botany professor Wayne P. Armstrong, describes the vast, and sometimes outlandish, variety of these phenomena: “Galls may be smooth, spiny or fuzzy, and resemble everything from marbles and ping-pong balls to dunce caps, saucers and sea urchins.” (See some of his intriguing photos here.)
In 2007, gall wasps had a baby boom in southern Maine. Residents were perplexed by a sudden abundance of small, fuzzy balls in their yards. The wasps inside these spheres, not the stinging kind, emerged to procreate and die, leaving behind a new generation and a new crop of galls to protect the infants.
These tiny galls, commonly called “fuzzy oak” galls, are only one example of what insects and trees can do together. Oak galls as big as basketballs have also been reported. Willow trees can grow what appear to be “pine cones,” quite puzzling to passerby, which are actually galls caused by tiny gnats. Christmas trees may also sport “cones” that are not what they seem.
The benefit of galls to insects is obvious, but humans have also found ways to use these creations. Fisherman break open goldenrod galls to get to the tempting larvae bait. Tannic acid is a gall-derived product, and fine inks are also made from galls. Galls have also been used as a spice, (mostly in the Near East), and as food for livestock. A good tip for campers–dry galls make excellent tinder.
Once you start seeking galls, they “appear” everywhere. Wayne’s Word reported that almost every individual sand aster in one 50-acre grassland area in southern California had a swollen stem tip gall on it. It’s hard not to become a fan of these diverse creations, perhaps even more so if you get to see them “hatch”. You can bring them inside for viewing—be sure you provide a jar with some moisture—and see what (well, who) emerges.
The photos of galls below are my own–not the most beautiful or technically precise images, but literally home-grown!