Weeding Nirvana or Weeding Neurosis
By Master Gardener Stephanie Wrightson
The most sustainable actions to PREVENT weeds include:
- Don’t bring weeds into the garden (use clean seed and soil; only composted manure; clean tools)
- Do not allow weeds to flower and reseed; pull, or cut at or below the soil line (crown)
- Use targeted drip irrigation to your ornamentals and crops during the dry season (weed seeds cannot germinate without moisture in the soil)
How we CONTROL weeds depends on whether they are annual weeds that live 12 months or less, biennial weeds that live for 2 years or perennial weeds that live more than 24 months. Plus, we want to control weeds by applying environmentally sustainable principles: minimally disturbing the soil, using targeted irrigation, avoiding the use of herbicides, recycling organic matter to use as mulch and choosing the right plant for the right place which promotes healthy plants that are better at withstanding the negative impact of weeds.
Some of the annual and biennial weeds in our Sonoma County gardens include, but are not limited to, chickweed, bur clover, bitter cress, groundsel (can be a perennial in coastal areas), crabgrass, mallow (sometimes a short-lived perennial), prickly lettuce, poa annua, filaree, spurge, purslane, scarlet pimpernel and bristly oxtongue. In a new garden bed, you may choose to “sprinkle-sprout-hoe.” That is, after an initial weeding, water your bed, allow the weed seeds to germinate and, when they are small seedlings, pull them or lightly hoe them (disrupting their root systems). Avoid bringing buried weed seed near the surface of the soil where they can germinate.
For annual and biennial weeds, take the following actions:
- Shallowly cultivate (hoe) or hand-pick weeds, AND
- Mulch at least 3 to 4 inches (to block sunlight)
Perennial weeds are usually viewed as “simple” or “creeping.” An example of a simple perennial weed is a dandelion. For these:
- Be persistent with hoeing/digging out; do not leave root segments
- Mulch helps, but some weeds persist through the barrier
- Ideally, remove perennial weeds as seedlings; if possible, leave no root segments or tubers; perennial weeds often require repeated cultivation which can starve roots over a number of years; some are impossible to obliterate in an organic garden—you only may be able to keep them at bay.
- After weeding, add a barrier (e.g., overlapping cardboard, burlap sacks or 6 layers of newspaper) along with 3 to 4 inches of mulch on top. Roots may survive and come up as the barrier material and mulch deteriorate, requiring your weeding diligence. Use of black plastic as a permanent barrier is discouraged as it kills organisms living in the soil, restricts air and water movement and, in general, does not improve soil condition.
Soil solarization may be used in extremely weedy situations when other non-toxic methods of control have failed—noting that is not very effective with field bindweed and other weeds with deep rhizomatous roots. Also note that, in sustainable gardening, we encourage a thriving population of beneficial organisms in the soil. With solarization, beneficial organisms are killed along with any pathogens, although the soil will be recolonized eventually.
Hopefully, being armed with knowledge and an action plan has reduced your weeding neurosis. Remember the basic rules for dealing with weeds:
- NEVER LET WEEDS GO TO SEED! NEVER!
- MULCH 3 to 4 inches to exclude the light required for seed germination and weed plant photosynthesis
- EMPLOY REGULAR AND RECURRING CONTROLS; eradicate weeds throughout the year
FOR MORE INFORMATION:
- Quick Guide to Sonoma County Weeds, Sonoma County Master Gardener website
- Weed Key, UC/ANR Integrated Pest Management
- Weed Photo Gallery, UC/ANR Integrated Pest Management
- Information by Specific Weed, UC Weed Research and Information Center
- California Noxious Weeds, California Department of Food and Agriculture, Plant Health and Pest Prevention Services