Virginia Tech Weed Identification Guide

Yellow Foxtail: Setaria glauca

Weed Description:  A clump-forming summer annual with a seedhead that resembles a fox's tail.  A weed of many agronomic crops, turf, landscapes, and nurseries.  Found throughout the United States, especially on fertile soil.
Seedling:  Leaves are rolled in the bud, leaf sheaths are without hairs, but the leaf blades have long silky hairs on the upper surface near the leaf base (shown in picture on left).  The ligule is a fringe of hairs approximately 1/2 mm long, often very difficult to see with the naked eye.

Roots:  A fibrous root system and stems that do not root at the nodes.

Stems:  Stems are erect, often flattened, without hairs (glabrous), reaching 3 feet in height, and often with a reddish tint at the base.

Leaves:  Leaf blades may reach 12 inches in length and 7 to 12 mm in width, and have long silky hairs at the leaf bases.  Auricles are absent and the ligule is a fringe of hairs reaching 2 mm in length.

Flowers:  The seedhead is a cylindrical bristly panicle, reaching 6 inches in length and 1/3-2/3 inch in width.   Spikelets are approximately 3 mm long, green, and each spikelet has 1-3 bristles that are 5-10 mm long.  The bristles turn yellow at maturity, giving the plant it's name.

Identifying Characteristics:  Characteristic foxtail-like seedhead that appears yellow when mature and leaves with long silky hairs at the base only, which helps to distinguish this weed from both Giant Foxtail (Setaria faberi) and Green Foxtail (Setaria viridis). Giant foxtail has many short hairs on the upper surfaces of the leaf blades, unlike yellow foxtail which only has a few long, silky hairs near the leaf base.  Similarly, green foxtail has no hairs on the leaf blades or at the leaf bases.