11 September 2008

Earthworms are the Culprits in the Spread of Ragweed Says the Weed Science Society of America

Here's an interesting tidbit you may have missed.
The Weed Science Society of America released this report.


Weed scientists discovered that “underground gardening” by earthworms is contributing to the spread of giant ragweed, a plant that causes sneezes and sniffles and is one of the nation’s most irritating weeds.

Earthworms help ragweed thrive by systematically collecting and burying its seeds in their burrows, said weed ecologist Dr. Emilie Regnier of Ohio State University.

In fact, we’ve found that more than two-thirds of all giant ragweed seedlings emerge from earthworm burrows.

The study focused on Lumbricus terrestris worms – commonly known as nightcrawlers.

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. The worms feed on plant litter they collect from the soil surface and store inside their narrow, underground homes. As the litter softens and decays, it improves the availability of nutrients in the soil. Now, though, it appears there is also a dark side to the earthworm’s work.

Our study shows that nightcrawlers are some of nature’s most effective weed farmers, Regnier said. They actively forage for weed seeds, pull them into their burrows and then ‘plant’ them under up to several inches of soil.

In fact, researchers found that worms collected and buried more than two-thirds of the seeds dispersed by a stand of giant ragweed. Each burrow examined in the study contained an average of 127 ragweed seeds, or 450 seeds per square foot.

While nightcrawlers collect seeds from other plants as well, giant ragweed is definitely on their preferred list.

We found the worms collect and bury 10 types of seeds in the same size range, Regnier said. But they have three special favorites – giant ragweed, bur cucumber (Sicyos angulatus) and sunflower (Helianthus annuus).

The link to the story came to me on the
National Gardening Association's blog.

1 comment:

Dee/reddirtramblings said...

Eeek!!!~~Dee