ABSTRACT
The western part of the distribution range is inhabited by the slender plants with small panicles and narrow leaves that are commonly classified as Sorghum halepense. The more robust specimens that inhabit the eastern part of the range are usually recognized as S. miliaceum. Since both taxa cross readily with one another, and hybrids among them are as fertile as their parents, they are considered to belong to one biological species, S. halepense. Different ecotypes of this species had been introduced as weeds to all subtropical and warm temperate regions of the world. Due to its wide distribution and hybridization with different varieties of grain sorghum, a spectrum of flowering responses is to be expected in S. halepense. However, information on the environmental control of flowering in this formidable weed is very scanty. Earlier flowering in northern latitudes is probably an adaptation to avoid autumn frost damage during the reproductive development.
