Weeds are just plants growing in the wrong place. They are not inherently evil, but they multiply rapidly and compete with desirable plants for water and nutrients. They can crowd out seedlings and harbor insects and diseases that spread to other plants. As a result, serious gardeners pay attention to weed control.
There are many approaches to weed control including the use of selective and broad-spectrum herbicides. Although there is a time and place for use of these chemicals, non-chemical methods can hold weeds in check while protecting the environment. Here are just a few ideas.
Avoid bringing weeds into your garden. Buy weed-free seed and mulch; remove any weeds that arrive with newly purchased plants.
Do not put weeds in your compost pile. Home composting temperatures often are not high enough to kill weeds or their seeds.
Minimize open spaces in your garden with one of the following:
• Take steps to increase the vigor of desirable plants so that they grow well and fill up the available space. Select plants that are suited for the climate and the site and care for them properly. Space plants at the minimum recommended distances to shade and further crowd out weeds.
• Apply organic and inorganic mulches. Organic mulches such as sawdust, bark, straw and pine needles when applied in a layer 2-5 inches deep will inhibit the emergence of weeds. Inorganic mulches such as black plastic and newspaper inhibit weed growth by blocking sunlight and preventing photosynthesis.
• For annual vegetable or flower beds that lie fallow during the fall and winter, consider sowing a cover crop. But don’t let the cover crop go to seed in the spring because the cover crop itself can become a weed.
Deprive weeds of what they need to grow. Directed watering (that is irrigating your garden in such a way that only the desirable plants receive water) and careful placement of fertilizers close to desirable plants inhibit the germination and growth of weeds.
Study your gardening enemy
If weeds appear, take quick action. The first step is to identify the weed and how it spreads.
Annual weeds germinate, flower, set seed, and die within a single year. Little bittercress, chickweed and lambquarters are examples of annual weeds.
All annual weeds spread only by seed. Therefore, the best non-chemical method for controlling annual weeds is to prevent their flowers from going to seed by pulling or cutting the weed at ground level before it flowers. In a pinch you can prevent future generations just by removing the flowers themselves. (But with the latter approach, the weed might continue to produce flowers and will still compete with your desirable plants for water and nutrients.)
Perennial weeds are plants which live for many years, and do not die after flowering. All perennials have underground parts that store food over the winter and allow them to reemerge in the spring. Scotch broom, Canada thistle and bindweed are examples of perennials.
Perennials spread by seed and underground parts of the plant (such as roots, tubers and rhizomes). Preventing their flowers from going to seed and removal of underground parts will theoretically control perennial weeds. Complete removal of roots, tubers and rhizomes, however, is extremely difficult and weeds often spring from the bits and pieces left behind.
A better approach is repeated mowing of the above ground portions of the weed which will deplete the weed’s food reserves. When undertaken while the weed is actively storing sugars in the roots and repeated for several seasons in a row, this approach can successfully weaken even the most stubborn perennials weeds.
Weeds spread quickly. Prevent them from ever appearing in your garden and take quick action when they do. Through a combination of prevention and control measures and a little persistence, you will prevail.
Jeanette Stehr-Green is a WSU-certified Clallam County Master Gardener.