Urban Agriculture
University of California
Urban Agriculture

The Case for Removing Weeds From Growing Areas

One point I always make is that the sooner you control annual weeds, the better. This reduces crop-weed competition, along with a host of other issues caused by weeds (we'll save that for another blog). But the real key to forward-looking weed management is to kill the weed before it produces seeds. Once seeds are produced, they contribute to the seed bank, pretty much ensuring that the weed population will be a continual problem.

But suppose you miss some weeds that are starting to flower but the flowers aren't open yet? I think most growers will just pull or cut the weed and leave it in or near the field.  

I want to show you a time-lapse video I took. I cut the flowering stem off of an annual sowthistle plant and took a photo with a special camera every minute for 6 days. As you can clearly see, even though the stem was no longer receiving water or nutrients from the soil, at least the flower bud continued to mature and produce seeds. Now, having said that, I have not germinated the seeds to see if they are viable, but there is a good chance they are. Click HERE for video. It's about 1 1/2 minutes long, but most of the action happens in the first 50 seconds.

So the take home message - if the weeds have flower buds starting to open, remove them to covered piles, trash cans, or other area where they will not be a source of new weed seeds. 


Posted on Monday, April 13, 2015 at 2:18 PM


A plant is only a weed in the eye of the beholder. Many "weeds" are edible and medicinally useful. Perhaps an article on the identification and cultivation of plants that may sometimes be called weeds because they are not known to the grower?

Posted by Harriette on May 3, 2016 at 11:31 AM

If you would like more information about weed identification, please these useful online tools from the UC Integrated Pest Management Program and the UC Davis Weed Research and Information Center.  
http://ipm.ucanr.edu/PMG/weeds_intro.html (click on "Broadleaf Identification", "Grass Identification", or "Sedge Identification")  

Posted by Valerie Borel on May 5, 2016 at 9:52 AM

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