Oaks, Acorns and You

Image Gallery Mark Moffett/Minden Pictures

MOTHER's Nature

Jerry Krautwurst

Magnificent oak trees and their acorns sustain countless wild creatures.

BLAM! BONK-BLAM! BLAM! For days on end at our house, this is early autumn's tune—a slow, staccato solo for pickuptruck percussion in A (for annoying) minor. No matter where I move my truck in our tree-covered driveway it sits beneath an oak, and acorns come raining down on it like oversized hailstones on a tin roof.

As startling as each resounding impact is to me, it must be a truly jarring experience for the little weevil larva curled inside the meat-filled shell. By summer's end many acorns carry the larvae, one to a nut, deposited as eggs in tiny pinholes drilled by feeding adult weevils. The jolt of an acorn's fall to the ground signals to the larva that the time has come to bore its way out of the shell. Once hatched, the larva burrows as much as a foot deep into the soil, where it remains for up to five years before pupating and emerging as a full-grown acorn-sucking beetle. The slam against unforgiving truck metal has to be a whole different kind of wake-up call.

Equally as eye-opening to biologists and ecologists, though, is the reverberating environmental impact of acorns—the countless billions that land with a gentle thud, and a collective bang, on soil and leaf litter from coast to coast. Scientists are only beginning to unravel the extraordinarily complex interplay between plants, wildlife and acorns in woodland ecosystems.

IN A NUTSHELL

Like other nuts, an acorn is a seed, an embryonic tree-to-be wrapped in a hard shell. But only the lower end of an acorn's innards is occupied by a rudimentary root and stem; the rest is nutritive tissue loaded with protein, carbohydrates and fat. Its purpose is to sustain a sprouting seedling until the infant grows green leaves and can stock its own larder via photosynthe sis. But far more often than not, a forest creature gobbles the nut and its stored nutrients first.

Upwards of 100 species of birds and animals include acorns in their diets. For many—including gray squirrels, blue jays, black bears, chipmunks, ruffed grouse and deer mice—nuts are the main food source, a critical element of day-to-day survival. For many more, acorns are a lifeline to spring and beyond. Without the benefit of the nuts' energy, those birds and animals will starve or fail to reproduce successfully.

Fortunately, the United States is blessed with roughly 58 species of native oaks. I say roughly because many oaks readily hybridize, producing pesky crosses that feed the fires of the ongoing debate among biologists over what, precisely, makes a species a species. Scientists will likely never agree on the exact number of different oaks. Regardless, they all produce acorns. The nuts range from peasize (willow and pin oaks) to whopping jawbreaker-size (bur and white oak). In a good year, one tree can produce thousands of acorns, and an acre of oak woodland can yield a quarter-ton or more of nuts. And there, in a nutshell, is an important environmental catch: not all years are good years.