Organic gardeners have more to sneeze at

If you steer clear of synthetic fertilizers and insecticides, compost religiously, and dig up your garden beds by hand, you're certain to have more earthworms than non-organic gardeners will. That's a good thing overall, since earthworm activity naturally loosens and aerates deep layers of the soil, and earthworms make soil nutrients more readily available to your plants. But, earthworms can be troublemakers, too. Turns out they have a lot to do with the tall stands of giant ragweed presently in bloom -- and, by extension, the accompanying hay fever many of us must suffer through.

For more than 10 years, Emilie Regnier, an Ohio State University weed ecologist, has researched the connection between nightcrawler behavior and ragweed's ability to survive -- and even thrive -- despite the fact that the mature plants don't produce many seeds. "Earthworms help ragweed thrive by systematically collecting and burying its seeds in their burrows. In fact, we've found that more than two-thirds of all giant ragweed seedlings emerge from earthworm burrows," Regnier says in a recent news release from the Weed Science Society of America.

Regnier, along with Ohio State's Kent Harrison and entomologist Clive Edwards, discovered that nightcrawlers seek out seeds and carry them deep underground, averaging 127 ragweed seeds per earthworm burrow. That works out to 450 seeds per square foot, so it's no wonder ragweed fares as well as it does. (Unfortunately, when the weed runs rampant, corn and soybean farmers are also hard hit. According to the Weed Society of America, farmers have reported yield losses of up to 75 percent in some cases!)

Researchers still aren't sure just why the worms fuss with all those seeds, but it's possible they're feeding on the seeds' tough exteriors or using them to strengthen their burrow walls. What's more, nightcrawlers inadvertently "farm" more than just giant ragweed. They're fond of several other seed varieties, including the bur cucumber and sunflowers. Still, giant ragweed's primarily to blame for farmers' crop losses and our own runny noses and itchy eyes. So, should you spot any of the plants growing in your garden, try to yank them long before they can set their seed.