General Description: A summer annual with an erect to sprawling or kneeling habit. It can form large loose tufts and usually grows to 3 ft (1 m) in height.
Seedling: The first leaf blade is lanceolate to linear, about 5 times longer than wide and opens parallel to the ground. Leaves are rolled in the bud and lack auricles. The ligule is a fringe of hairs approximately 1 to 2 mm long. Blades are 2 to 3.5 cm long and 5 mm wide. The first few leaves, sheaths have dense 1 mm long hairs and rough margins. Collars are also densely hairy. Seedlings become less hairy with age and completely lack hairs at maturity. Plants often have a purplish coloration. Mature Plant: Leaves are similar to those of seedlings, and the ligule is a fringe of hairs 1 to 3 mm long. Stems often have a waxy appearance, and the swollen and irregular lower nodes give the stem a zig-zag appearance. Blades are smooth on both midvein is conspicuously light green to white. Sheaths are smooth (rarely hairy), purplish, and slightly compressed. Collars are continuous and broad. Flowers and Fruit: Flowers are produced from July to October. The seedhead is a large, freely branched, spreading panicle, 10 to 40 cm long, which may appear purplish at maturity. Spikelets are 2.5 to 3.0 mm long, 2.0 mm wide, and straw-colored to purple-tinged. Spikelets produce 1 smooth, dull yellow to brown seed (1.5 to 2 mm long). Distribution: Found throughout the United States. Crops Affected: Corn, Soybean Animal Poisoning: None Similar Species: Witchgrass is closely related to fall panicum but is very hairy throughout, even at the seedling stage. Foxtails (giant, green, yellow, and bristly) also have a hairy ligule and can resemble fall panicum in the seedling stage; they can be distinguished by the location of the hairs, which are on the lower surface of the fall panicum leaf blade but on the upper surface of the foxtail leaf blades or absent altogether. Young foxtail seedlings can be distinguished from those of panicum by seed shape and shininess. Foxtail seeds are fat and dull; panicum seeds are slender and shiny. Johnsongrass has a distinctive white midvein and a panicle inflorescence similar to that of fall panicum; however, johnsongrass is a rhizomatous perennial with a membraneous ligule that is sometimes fringed at the top.