Are Weeds Completely Useless?
A weed is any plant that is growing where we don’t want it to grow. For example, such weeds as dandelions and crab grass spoil the looks of lawns. Weeds hurt crops because they take minerals and water from the soil.
Some weeds grow tall and shut off sunlight from the plants that we try to cultivate. Many plants whose seeds scatter easily are called weeds, because they come up unwanted in many places.
Weeds are not, however, completely useless. Some weeds serve as food for wildlife. Weeds help to keep soil from washing away after heavy rains.
A number of weeds, such as the dandelion and lamb’s quarter, are edible, and their leaves or roots may be used for food or herbal medicine. Burdock is common over much of the world, and is sometimes used to make soup and medicine in East Asia.
Some weeds attract beneficial insects, which in turn can protect crops from harmful pests. Weeds can also prevent pest insects from finding a crop, because their presence disrupts the incidence of positive cues which pests use to locate their food.
Weeds may also act as “living mulch”, providing ground cover that reduces moisture loss and prevents erosion. Weeds may also improve soil fertility; dandelions, for example, bring up nutrients like calcium and nitrogen from deep in the soil with their tap root, and clover hosts nitrogen-fixing bacteria in its roots, fertilizing the soil directly.
The dandelion is also one of several species which break up hardpan in overly cultivated fields, helping crops grow deeper root systems. Some garden flowers originated as weeds in cultivated fields and have been selectively bred for their garden-worthy flowers or foliage.
An example of a crop weed that is grown in gardens is the corn cockle, which was a common weed in European wheat fields, but is now sometimes grown as a garden plant.