Pests in Gardens and Landscapes: Quick Tips

Weeds in Landscapes

Published   6/23

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A sharp scuffle hoe will cut weeds near the soil surface. Photo by Jack Kelly Clark.

A sharp scuffle hoe will cut weeds near the soil surface. Photo by Jack Kelly Clark.

Yellow nutsedge growing through a shallow layer of mulch. Photo by Jack Kelly Clark.

Yellow nutsedge growing through a shallow layer of mulch. Photo by Jack Kelly Clark.

Weeds will invade any bare area in a landscape including pots, raised beds, or anywhere space and soil are available. Prevent weeds by planning ahead for new planting areas and using a combination of competitive plants, mulches, and weed removal by hand. Removing aggressive perennial weeds before they set seed is especially important. You should rarely need herbicides.

Before and right after you plant:

  • Prepare the site and control existing weeds.
    • Dig out weeds or remove by hand. Follow up by irrigating, then removing newly emerged weed seedlings right before planting.
    • Solarize the soil if conditions allow.
    • If necessary, use a systemic herbicide for difficult-to-control perennial weeds.
  • Check your soil for compaction and amend if needed. Make sure new soil comes from a reputable source and doesn’t contain weed seeds.
  • Establish new plantings as quickly as possible to cover bare areas and shade out weeds.
  • Consider drip irrigation in permanent plantings.
  • Apply mulch.

Mulch is the key to weed-free landscaping.

  • Mulches prevent weed seed germination by blocking sunlight. Properly apply mulch and replenish it so it continues to suppress weeds.
  • Organic mulches (e.g., wood chips, bark chips, compost) are attractive but must be replenished once they break down. Choose a medium-sized mulch (3/4 inch) and keep at a depth of 3 to 4 inches.
  • Natural inorganic mulches (e.g., sand, gravel, pebbles) are more stable than organic mulches but difficult to keep clean.
  • Landscape fabrics are porous and long lasting and vary in how long they remain effective. Cover with organic mulch.
  • Black plastic is not preferred since it can restrict air and water movement and promote root rots.

When weeds invade your landscape:

  • Remove young weeds by hand before they flower and set seed.
  • Use a dandelion knife or similar tool to dig up all roots and underground parts of perennial weeds without overly disturbing the soil.
  • Use shallow cultivation or hoeing to remove annual weeds from ornamental plantings.
  • Consider devices such as string trimmers for large areas.
  • Apply mulch to weed-free areas to prevent further invasions, and regularly remove new weeds as soon as they appear.

What about pesticides?

  • In general, existing landscape plantings don’t need herbicides; hand weeding and mulching usually control weeds.
  • Use herbicides for special weed problems or for difficult-to-control perennial weeds.
  • Herbicides can injure desirable plants in the landscape, so use these products with great care.

Read more about Weeds in Landscapes.

Minimize the use of pesticides that pollute our waterways. Use nonchemical alternatives or less toxic pesticide products whenever possible. Read product labels carefully and follow instructions on proper use, storage, and disposal.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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