NDSU Extension - Stark & Billings County


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Controlling Garden Weeds Without Chemicals

A good reason to grow your own vegetables is to have an excellent source of nutrition with minimal or no use of chemical pesticides. In most instances, weeds are not a major problem if you practice good sanitation. This means weeds in the garden need to be controlled early because they often bring insects that alternately feed on them and your developing vegetables, causing damage and transmitting diseases.

Annual weeds generally have long simple taproots and can often be easily killed by hoeing or hand pulling. Annual weeds cannot be completely eliminated as the soil is loaded with seeds. One of the best approaches is to use various mulches to suppress annual weed emergence and growth.

Perennial weeds often have complex horizontal root networks and can’t be easily removed via tillage, hoeing or hand pulling. Prevention is key. Start clean and don’t plant into established perennial weeds. Dig to remove the plants, roots and all. A garden fork works well to loosen roots. For bad patches, cover soil with clear plastic and allow to solarize over a summer. Otherwise, smother with heavy mulch or weed barrier, then remove emerging shoots immediately and often-starve the roots.

What to use as a mulch?

  • Plastic mulch (clear, black or colored) is relatively inexpensive and suppresses most annual weeds well.
  • Straw or hay needs to be several inches thick and decomposes relatively quickly, adding nutrients. Either can contain weed seeds, and may harbor pests.
  • A dense stand of annual weeds can be cut or pulled and used as a mulch. A weed mulch will suppress weeds and break down, adding nutrients to the soil.
  • Wood chips or shredded bark suppress weeds at 2 to 3 inches deep. They also will moderate temperatures, keeping plants cooler during summer and warmer during winter.
  • Grass clippings are good mulch for gardens, however do not use lawn clippings unless you know the history of their exposure to herbicide. In most cases, lawns should be mowed at least three times before using the clippings for mulch.
  • Other mulch suggestions are deciduous tree leaves, newspaper and cardboard.

Do not use rock mulch, which is a heat trap. Rock mulch harms the soil as its heavy weight compacts the ground and destroys air pockets needed for roots to grow.

Filed under: mulching, mulch, Weeds
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