Plants must meet two criteria to be considered for admittance into that elite group of plants known as weeds. First it must specialize in growing in soil that has been disturbed by human activity. Equally important it must cause humans some annoyance (if it doesn’t then it’s merely a pioneer species). This definition of weeds takes us beyond the familiar annual or perennial species, to include woody shrubs such as Blackberry and Broom, or even trees like Cottonwood, Birch and Mesquite.
Weeds are nature’s first line of defense against soil degradation and have an essential role in maintaining and increasing soil fertility. When she quickly covers your newly dug planting bed with a vigorous crop of weeds, she is telling you that you should never have left the surface of the soil bare. You should always cover it with something.
The importance of weeds
Weeds are natures soil-improving crops and they should be ours too. Deep-rooted weeds are beneficial in that they mine minerals from the subsoil and bring them to the surface where they become available to other plants. Tap rooted species can break up compacted subsoil and when they die and decay these become channels for aeration and soil life. The accumulator plants have the ability to forage for scarce nutrients and concentrate them in their tissue.
A flush of weeds makes a useful self-sown cover crop to protect and enrich the soil. The hardier species can act as a cover crop, to protect the soil and store nutrients over the winter. These should be dug in or composted before they set seed in spring.
Weeds also provide cover and food for wildlife, including predatory and pollinating insects, birds, toads and more,
Fast growing weeds produce an abundance of organic matter, which feeds and stimulates soil organisms.
Weeds are useful as companions and nurse plants. They help to camouflage crop plants and hide them from insect pests and can even act as trap crops. For example many Brassica pests are more attracted to wild Brassicas (with their abundance of pungent oil) than to the rather insipid cultivated varieties.
Many common weeds are edible and / or have medicinal properties (maybe mother earth decided to give us some consolation for the hassle of weeding). Dandelion, Winter cress, Plantain, Lambs Quarters, Chickweed, Burdock, Amaranth, Purslane are all great food plants, if gathered at the right time and prepared properly (most have actually been cultivated at one time or another). When you start to use the edible weeds, you realize they are often fully equal in flavor to the crops you are trying to grow and a lot more nutritious. It’s actually pretty silly planting and pampering your spinach and then ripping out the equally good (or better) Lambs Quarters or Pigweed.
Weeds should be looked upon as another productive layer for the garden and are especially significant because they grow without you having to do anything. In fact you would be removing them anyway, even if you didn’t eat them (and eating them is better than composting them.)