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How weeds spread

By Joe Julian, Colorado State University Cooperative Extension, Horticulture/Entomology

Common garden weeds spread either by human action or through the forces of nature. Virtually none of the weeds we contend with are native to North America. Crabgrass, for example, came from Eurasia; purslane from western Asia and quackgrass from Europe.

Seeds move via the wind or they are carried by birds. They may be carried in the hair, fur or intestinal tract of animals that transverse long distances. Sometimes grasses, with their seeds intact, are carried in the ocean currents until they find a landing spot. On a more local level, seeds can move into our yards via straw, hay or animal manures. Weed seeds can even be mixed with grass seed or turf, so when you seed or sod your lawn, you could be importing a crop of weeds too.

Photo: Judy Sedbrook

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Date last revised: 01/05/2010