The Biology of Canadian Weeds: 155. Panicum miliaceum L.

Proso millet, Panicum miliaceum L. (Poaceae), has been a crop in Asia and Europe for 10 000 years and for over 300 years in Canada, where it is grown for grain, rescue crops, birdseed, forage, and recently for swath grazing. Crop-like biotypes have escaped from cultivation throughout Canada, but these infestations were generally temporary. Probably the first persistent, weedy biotype in Canada (Quebec) has large, dormant, dark red seeds. Its eradication has been attempted for many years. In the 1970s, a worse problem, a black-seeded biotype with many weedy attributes, including shattering as seeds ripen and strongly dormant seeds distasteful to many birds, spread across southern Ontario and became labelled as noxious. Concurrently, it was described as the worst weed in the US Corn Belt. In the 1980s, Canadian studies revealed infestations of other weedy biotypes, differing in seed colour and other attributes. Panicum miliaceum is an extremely variable species world-wide. Since the late 1990s, weedy proso millet has declined dramatically after the adoption of newer herbicides, particularly glyphosate. This development may lead to increases in cultivated proso millet, especially where climate change favours short-season crops grown under drier conditions.