What Is a Weed?
A weed is any plant that grows where people don’t want it to grow. For example, when we plant a lawn, we don’t want other plants growing in the lawn. Other plants spoil the appearance of the lawn, and take minerals and water from the soil that the lawn needs. So we call any other undesired plant a weed.
Plants whose seeds scatter easily are usually called weeds because they come up in many unwanted places. However, weeds are not always useless. Some serve as food for wildlife. Also, weeds hold the soil in place, and help to prevent erosion.
Many plants that people widely regard as weeds also are intentionally grown in gardens and other cultivated settings. The term also is applied to any plant that grows or reproduces aggressively, or is invasive outside its native habitat.
While the term “weed” generally has a negative connotation, many plants known as weeds can have beneficial properties. 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.