One can’t help but admire an acorn’s economy of form. The rough-textured cap is an enlarged and stiffened version of the small, overlapping leaves that protected the female flower before it blossomed. The smooth-textured acorn is the flower’s ovary, grown large and hardened into a protective shell around the single seed within.
A white oak (“Quercus alba”) 24 inches in diameter can produce 2,000 or more acorns per year. But several years may pass without any hard mast at all. Scarlet and chestnut oaks produce a decent crop about every four to five years. This is because it takes a lot of energy to bear fruit. Oaks and many other plants “discovered” that it’s generally most beneficial to fruit profusely one year, saturate the environment, and then lay low for a few years. This strategy contributes to lean mast years that harm numerous animals which are highly dependent upon acorns. Before the American chestnut was eliminated as a significant mast producer during the early twentieth century, it helped to alleviate this situation. Chestnut trees tended to bear more evenly from year to year, thereby offsetting the oak’s lean-year cycles.
We know that numerous plants and animals have evolved relationships that are mutually beneficial. None is more effective than the one forged between gray squirrels and oaks. Unlike red squirrels (also know as “boomers”), which primarily feed on seeds from conifers like eastern hemlocks, a gray squirrel at work seems to have been trained to propagate oak trees. It carries each seed from 50 to 100 feet from its parent, scratches a hole of just the right depth in the soil, deposits the seed therein, and covers it with soil. This process is repeated endlessly so that gray squirrels never recover via smell and memory all of the acorns they plant. The second-most prolific distributor of acorns is the blue jay, which can carry two acorns at once: one in its throat pouch and one in its mouth.
There are, of course, many other animals that eat acorns: bears, raccoons, birds, and us human critters. Humans aren’t big acorn eaters these days, but the early European settlers and all the Indian tribes once consumed them in great numbers, having devised different methods for leaching out the bitterness. They were buried in wet ground or sometimes soaked in streams until the tannic acid was mostly gone. According to Thomas E. Mails’ The Cherokee People (1992), that tribe used acorns “dried, hulled, and pounded. The meats were then put into a leaching basket, and a cloth was tied over the top. Water was dripped on the cloth throughout the night, soaked into the meal, and then ran out through the bottom of the basket. The strong, bitter taste of the original acorn was removed, and the final product could be rendered into bread.”
Acorns in the white oak group (rounded leaf lobes) contain less tannin than those in the red oak group (sharp-pointed leaf lobes) and are preferred. Acorns are rich in both fats and carbohydrates. If you’re interested in current methods for rendering acorns into palatable foodstuffs, consult Rebecca Rupp’s Red Oaks and Black Birches: The Science and Lore of Trees (1990), pp. 18-21.
Have you ever noticed the numerous tiny holes in acorns? Like squirrels, humans experienced in acorn gathering don’t harvest those with small holes in them because they indicate the presence of acorn weevils and moths. Female acorn weevils drill holes in acorns with elongated snouts and lay eggs therein. These hatch into grub-like larvae that feed on the acorn before emerging through yet another hole and falling to the ground. Then, along comes a female acorn moth that lays its eggs in the weevil entrance and exit holes. These hatch into larvae that feed on what’s left of the acorn. Accordingly, it’s not surprising that hollow acorns are often encountered.