Setaria viridis aka Green Bristle Grass

Setaria viridis, also known as green foxtail, green bristlegrass, and wild foxtail millet, is a hardy grass that is native to Eurasia but is now found on most continents as an introduced species. It is an annual grass with decumbent or erect stems that can grow up to a meter long, with leaf blades that are up to 40 centimeters long and 2.5 centimeters wide. The inflorescence is a dense, compact, spikelike panicle up to 20 centimeters long, growing erect or sometimes nodding at the tip only. The spikelets are 1.8–2.2 mm long and are subtended by up to three stiff bristles. Setaria viridis is closely related to Setaria faberi, a noxious weed, and is often confused with it. However, S. viridis has glabrous leaves and an erect or nodding inflorescence, while S. faberi has sparse, soft hairs on the leaves and a nodding inflorescence. Foxtail millet (Setaria italica) is another close relative of S. viridis, but it has larger spikelets about 3 mm long and usually smooth, shiny upper lemmas. Foxtail millet was cultivated in China by 2700 BC and during the Stone Age in Europe. S. viridis is the wild antecedent of the crop foxtail millet and has been proposed as a model to study C4 photosynthesis and related bioenergy grasses. It has a short life cycle of 6-8 weeks, is transformable, and is currently being sequenced. Genetic resources are currently being developed by a number of groups. A method to break the prolonged seed dormancy has been discovered recently, which could contribute to making S. viridis a choice monocot genetic model system. This grass is a summer annual that branches at the base to form a small tuft of leafy culms. In open areas, the slender culms are erect, ascending, or widely spreading. The blades of the alternate leaves are light to medium dull green, hairless, and up to 6" long and ½" across. The open sheaths are light to medium green like the leaves, but slightly more shiny, and wrap around the culms loosely. At the junction of each blade and sheath, the ligule is defined by a ring of white hairs. The green bristlegrass refers to the foxtail-like inflorescences of the weedy and aggressive annual grass, Setaria viridis.