Regional Gardening Reports :: National Gardening Association

In the Garden:
Middle South
September, 2011
Regional Report

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This handful of green acorns, which fell from white oak trees 6 to 8 weeks early because of drought stress, are less than mature size.

All Acorns Not Created Equal

Where the weather is concerned, it seems the only thing we can count on these days is the knowledge that we can't count on anything. Though it's typically hot and dry in my area in late-summer, the weather has been brutal since mid-July when temperatures soared to three digits and all signs of precipitation disappeared. Though the heat has abated somewhat in recent days, there is still no rain and many trees are dropping leaves prematurely.

Unfortunately, oaks are dropping their acorns early too. The circular driveway in front of my house, sheltered by towering white oaks, is currently littered with green nuts that are roughly half their mature size.

My two small dogs love the novelty of this new prize and continually try to pick them up in their mouths, which is not a good thing. Acorns are a keystone food for wildlife, but they contain tannin, a compound which is poisonous to most domestic animals and livestock.

Pigs, as you may know, are the exception. In Spain, "acorn-finished" pork is highly prized and sold for astronomical sums. Farmers in the U.S. might remember that acorn foraging was common here, too, until the 1940s, when it was discouraged as poor forest management.

Nonetheless, acorns are one of the most important resources for wildlife in the deciduous forests of our region. Rich in protein, carbohydrates, fats, and a number of minerals and vitamins, they're a staple for bears, deer, turkeys, ducks, woodpeckers, squirrels, mice, and many other animals and birds.

Not all acorns are created equal, however.

The white oak acorns that litter my driveway are usually large, meaty, and relatively tasty, but they contain only a fraction of the nutrients found in the acorns of red oaks, which are much smaller and more bitter. As you would expect, the white oak's sweeter-tasting acorns are quickly eaten or cached in autumn.

Acorns from red oaks, which take two growing seasons to mature as opposed to the one of white oak acorns, are more bitter because they contain a higher percentage of tannin. The compound which makes them unpalatable, however, also acts as a natural preservative, protecting them from bacteria and insects once they fall to the ground.

As months wear on, the tannin, which is water-soluble, leaches from the red oak acorns. So by the end of winter, when food for wildlife is especially scarce, this nutritious fruit is finally fit to eat.

Even humans can eat acorns when tannin is removed, and many do. Native Americans blanched the tannins from oak nuts by bagging them and putting them in a flowing stream. Today, those who collect and process the wild edibles boil them repeatedly, until the water no longer contains any trace of brown.

After tannins are removed, acorns have a mild, sweet taste. They can be eaten dried or roasted, or coated with sugar to make candy. In past years when coffee prices were exorbitantly high, roughly ground acorn served as a substitute, but it never proved to be popular. Most people find the nuts more useful when ground into a fine meal and made into breads or cakes, or used in soups or stews.

Although acorn production of both white and red oaks is predictable, it is never dependable. Even when the weather is favorable, trees may or may not produce large quantities of nuts. This seed production strategy, known as "predator satiation," periodically limits nut production to reduce animal populations, and then produces a bumper crop so some seeds can escape predation and germinate to perpetuate the species.

This year would have been a good one for acorns, but drought stress has made it too costly for the trees to expend more energy on the production of seeds that cannot sprout in bone dry weather, so the trees are aborting their current crop for the chance to produce viable seeds in the next growing season.

Rain is in our forecast thanks to a tropical storm in the Gulf of Mexico, but will it be too little, too late? Only time can tell. If there are not significant numbers of mature acorns falling from both white and red oaks in October, it could be another long, hungry winter for wildlife.

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