Feral cannabis, or wild marijuana (often referred to in North America as ditch weed), is wild-growing cannabis generally descended from industrial hemp plants previously cultivated for fiber, with low or negligible amounts of psychoactive tetrahydrocannabinol (THC).
The Drug Enforcement Administration defines ditch weed as "wild, scattered marijuana plants with no evidence of planting, fertilizing, or tending". Industrial hemp was widely cultivated in the American Midwest in the mid-20th century, particularly to support the war effort during World War II, and since that period the plant has re-seeded naturally and grown wild in states such as Oklahoma, Missouri, Nebraska, Iowa, and Minnesota, with Indiana reporting the largest concentrations nationally.
As early as 1914, a United States Department of Agriculture publication stated: "Hemp is abundant as a wild plant in many localities in western Missouri, Iowa, and in southern Minnesota, and is often found as a roadside weed throughout the Middle West.