Some of the plants which grow in our garden are the ones we planted, and others - frequently much more numerous - are plants that grow on their own, taking advantage of the ecological niche of open soil and fertility that we provide. These are often considered weeds.
For successful gardening it is useful to know the weeds and their habits. Get a good plant identification book and read, for example, Stalking the Wild Asparagus by Euell Gibbons to gain an appreciation of these plants.
Not all weeds are alike. Some weeds, like lambsquarters (which indicate fertile soil) and purslane are found in almost every garden and are as tasty and nutritious as many of the vegetables we cultivate. Many weeds like red-root pigweed and ragweed grow very fast and will shade out vegetables like carrots and onions which need lots of light and grow slowly. Low, slower growing weeds like chickweed or groundsel, growing among corn, or pole beans, have little effect except to shade the soil. Weeds like leguminous clover growing in the corn will actually help the corn grow by adding nitrogen to the soil.
Weeds such as the perennial grasses can be hard to pull out, whereas young pigweed and lambsquarters pull up very easily. If you leave a piece of the stolon or root of quack grass or mugwort in the ground it will grow a new plant. Mint, a valuable herb, spreads the same way and can become a weed if not contained. Cut off just below the soil line, other weeds will die. And sometimes a weed turns out to be a beautiful and desirable new plant.
Most plants that are considered weeds produce vast quantities of seeds with a very long viability. These seeds sit in the ground just waiting for the right conditions to germinate, grow and reproduce. Cultivation (with a sharp hoe soon after the weed seeds germinate) cuts off the plants and stops most growth. The bigger the weeds get, the more likely that they will compete with our flowers and vegetables for sunlight, water and nutrients. The bigger they get, the more likely their root systems will become entangled with the roots of crop plants, making it harder to pull them out without disturbing other established plants. Weeding after a rain is always a good idea.
Chemical control of weeds in the garden with herbicides doesn't work. We want to grow too many different kinds of plants in the garden, and although some vegetables may not be killed by the chemicals, they may be weakened. Plants are too important for our continued existence on this planet for us to risk using chemicals which kill them. And herbicides are probably dangerous to our health.
A good strategy for controlling weeds is to mulch your garden. Traditionally, straw (the stems of grain plants) is used, because it is a natural product which is free of seeds and breaks down to nourish the soil. Hay is easier to get and works too, although it may introduce grass seeds into the garden. Grass clippings from a lawn free of herbicides make a good mulch. They are easy to apply because of their fine texture, and they provide some nutrients to the garden as well. Wood chips and sawdust will extract nitrogen from the soil to assist in their decay and may stunt the growth of vegetables. In dry times, the weeds you pull out can be laid on the soil as mulch. Unfortunately, if it rains or you irrigate, some of them will grow again. Any weeds not used this way, should be added to the compost pile (unless they have gone to seed) in order to return the nutrients they contain to the soil. All of these mulches encourage beneficial earthworm activity, and allow rain to penetrate. Black plastic mulch is sometimes used, but it is ugly, has disposal problems and doesn't let water penetrate.
Weeds can feed us, nourish and protect our soil, and tell us about its fertility. The more we learn about weeds, the better we can manage them for a more successful garden.
This is Bill Duesing, Living on the Earth
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