UC Master Gardeners: Keeping vegetable gardens weed-and herbicide-free

Q: The area planned for my vegetable garden is now full of weeds. What’s the best way to get rid of them and avoid herbicide use? 

-— Rick Lewis, Morro Bay 

A: You’re right in thinking you’ve got to eliminate weeds — they will compete with veggies for sunlight, water and nutrients, and likely win the competition. If you haven’t already planted, cultivate the top two inches of soil; rake to remove uprooted weeds; irrigate deeply; wait 10 to 14 days for new weeds to appear; cultivate again. This would give you a comparatively weed-free beginning to your garden.

If you’ve already planted, you need to start hand-weeding and hoeing—hard but satisfying work. Eliminate maturing weeds right away — each can spread hundreds of seeds that may remain viable in the soil for years. With persistence you can eventually arrive at a nearly weedless plot. Chemical herbicides are not recommended for home vegetable gardens. 

Mulch the garden after clearing out your weeds. Mulch starves seedling weeds and also saves water. Coarse mulch (bark, straw, etc.) should be spread three to six inches deep, and finer mulch (grass clippings, sawdust, etc.) spread one to three inches deep. Keep the mulch well away from plant stems to avoid rot. Organic mulch (straw, bark, etc.) may contain weed seeds, but weeds that appear after mulching can usually be easily pulled. Synthetic mulch (black plastic, etc.) works well against weeds but lacks the benefits of organic products and may interfere with air and water circulation. 

Elimination of weeds may also be achieved by “soil solarization,” a process that kills seeds by heating the soil for 40 to 60 days during the summer. Local Master Gardeners can provide information.