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Attack of the 50-foot weeds?


It's not even April and I've already found myself, on hands and knees, weeding in my garden. In particular, I've been poking around the asparagus and strawberry beds for signs of life. All I've found so far are the dried stubs of last year's asparagus stalks, several delicate strawberry crowns, and lots and lots of baby weeds. There are diminutive violet corms, scores of wild onion, and dandelions so small that they could actually be considered "cute."

The dandelions and wild onions, anyway, are edible at least. (As long as they haven't been sprayed with herbicides or pesticides, and as long as they're not full of pollutants from the nearest major highway, that is.) Most spring greens do taste best when picked while they're still tender and young. That's also the time to cull other kinds of weeds as well -- before they have the chance to crowd out the veggies, herbs, and perennial flowers we're actually trying to grow. But information from the U.S. Department of Agriculture's Agricultural Research Service suggests the weeds in our yards and gardens are becoming more robust and aggressive, thanks, in part, to global warming.

The USDA's Dr. Lewis Ziska studied the effects of rising carbon dioxide levels and warmer temperatures on weeds, and he determined that weeds grown in city settings grow to "four times the height of those in a country plot 40 miles outside the city," according to a news release from The Weed Science Society of America. "Additional work by Ziska also suggests that even recent increases in carbon dioxide during the last 50 years may have led to bigger poison ivy plants with a more virulent form of the oil that causes people to break out in a rash," the release continues. Worse yet, of the 45 major crops in the U.S., over 400 different types of weeds grow in conjunction with them -- and, while plants generally become more vigorous with increased carbon dioxide levels, Lee Van Wychen, the director of science policy for The Weed Science Society of America, states, "the impact of rising carbon dioxide seems to be far more pronounced in the weeds that compete with crops than in the crops themselves."