Crabgrass Carries On Chemical Warfare

Click here to listen to this podcast

Lawn enthusiasts love a lush, green carpet of grass. Which is why they hate crabgrass. And now, they may have one more reason to despise the weed. Because crabgrass isn't just faster-growing than the rest of the lawn. It may actually be poisoning the lawn, by pumping herbicide into the soil. That's according to a study in the Journal of Agricultural and Food Chemistry. [Bin Zhou et al, Crabgrass (Digitaria sanguinalis) Allelochemicals That Interfere with Crop Growth and the Soil Microbial Community]

Researchers crabgrass hydroponically, so they could easily capture any chemicals released by the plant's roots. Then they dripped that hydroponic solution into pots of wheat, corn and soybean seedlings. Two weeks later, they dried and weighed the seedlings. And sure enough, the crabgrass solution had significantly stunted the seedlings’ growth, compared to control plants. And since corn is in the same family as lawn grasses, the crabgrass toxic effect may also spell bad news for your beautiful Kentucky bluegrass.

The researchers still aren't exactly sure how crabgrass' chemical weapons work. But the weed can wipe out beneficial bacteria and fungi in the soil, too. So it’s possible that crabgrass poisons its neighbors directly, by releasing toxins, and indirectly, by creating inhospitable soil. Either way, it's bound to make lawn owners crabby.

—Christopher Intagliata

[The above text is a transcript of this podcast]

Follow Scientific American on Twitter @SciAm and @SciamBlogs.
Visit for the latest in science, health and technology news.

© 2013 All rights reserved.