A Weed by Any Other Name: Monocultures and Wild Species

Abstract

The control of weeds on the farm is a major expense and the problem is continually growing. Where do these weeds come from and why are they so problematic on farms? As many as 3,000 species of nonnative plants have become established and common enough to be considered “naturalized” (i.e., permanent residents) in the United States. That may seem like a large number, but 3,000 represents only 10 percent of the number of nonnative plants commercially available. It has been estimated that more than 1,500 (more than 50 percent) of all the naturalized species so far introduced to the United States came through “intentional” introductions of one sort or another. These introductions include food crops, herbs for medicines, herbs and spices for cooking, forage for livestock, and ornamental plants, as well as plants introduced for erosion control or even because they reminded human immigrants of their homelands. Many introductions might have been accidental or associated with agricultural activities: cows and sheep carry weed seeds in their fur and feces, and weed seeds are frequent contaminants in the crop seeds that we plant.