Advice from the Help Desk of the
Master Gardeners of Contra Costa County
Client's Request: I've been noticing this “weed” growing in my garden lately. At least, I think it's a weed although the leaves seem to resemble some garden geraniums. Is it a weed, and if it is, what do you suggest I do to get rid of it? Some JPG photos I took of the “weed” are below. ... and (editor's addendum) can you eat it?
MGCC Help Desk Response: Thank you for the photographs. The plant is a type of Mallow, probably “Little Mallow” (Malva parviflora), often also commonly called Cheeseweed for the "small wheels" of cheese like fruit it produces. And yes as the common name implies, it is a winter-sprouting annual weed or sometimes a biannual weed. It quickly develops a deep taproot, making it difficult to eradicate. Pulling them up or hoeing them off as soon as you notice them is the best way to control their spread.
Cheeseweed can also be toxic to cattle and can reduce egg quality if fed to laying hens.
Additional information on this weed and its control can be found at the University of California's website http://www.ipm.ucdavis.edu/PMG/WEEDS/little_mallow.html and http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74127.html.
As above, early-on mechanical (hoeing) and cultural control (weeding) are about the only effective controls for home gardeners. Control by herbicides has not proven effective. In fact, this mallow is one of the few weeds not controlled by glyphosate (i.e., RoundUp™).
I hope that this information is helpful. Good luck on controlling it. I've had them in my garden off and on for years and can't seem to keep them out although I find that if caught early enough they aren't hard to keep them at bay and aren't that much of a pest.
HOrT COCO Blog Editor Addendum: It's been brought to my attention that Cheeseweed is edible... and by quite a few cultures... but not by this gardener/editor... see the various comments on its use as greens, etc. by Googling "is cheeseweed edible?". You are on your own for that adventure though...
Help Desk of the Master Gardeners of Contra Costa County (JL)
Note: The UC Master Gardeners of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: firstname.lastname@example.org, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/blogcore/blogroll.cfm).