Scientists have long been mystified by the rapid spread of giant ragweed since it produces relatively few seeds. Now research shows the lowly earthworm is one of the culprits.

“Earthworms help ragweed thrive by systematically collecting and burying its seeds in their burrows,” says Emilie Regnier, weed ecologist at Ohio State University. “In fact, we've found that more than two-thirds of all giant ragweed seedlings emerge from earthworm burrows.”

Until now, nightcrawlers have had a stellar reputation among growers since their burrows promote water filtration and their eating habits help make nutrients more available to crops.

“We found the worms collect and bury 10 types of seeds in the same size range (as giant ragweed),” Regnier says. “But they have three special favorites: giant ragweed, burcucumber and sunflower.”

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