Setaria geniculata (Lam.) Beauv., knotroot bristlegrass 
DESCRIPTION 
Warm-season , weak, rhizomatous perennial. 
Height: 1 to 3 feet. 
Leaf blade: Flat; 6 to 10 inches long; 1/4 inch wide; promi- 
nent midrib; upper surface covered with soft hair. 
Leaf sheath: Rounded; generally shorter than internodes; 
often purple tinged. 
Ligule: Fringe of short hair. 
Seedhead: Spikelike panicle 1 to 2 inches long, yellowish; 
each spikelet surrounded by 5 or more yellow or purple 
bristles. 
GROWTH CHARACTERISTICS 
Grows from late March or early April until fall from short, 
knotty, branching rhizomes. Foliage is a distinctive whitish 
green. Base of plant is slender and wiry. Produces two and some- 
times three seed crops during one growing season — the first one 
during May or June. Bristles are left along the seedstalk after 
seed disseminate. 
DISTRIBUTION 
Massachusetts to Florida, west to California, north to Illinois 
and Kansas, and in South America. 
SITE ADAPTATION 
Grows best on moist or wet sites. In Florida, grows on wet 
sandy soils, sloughs, and acid flatwoods. In Texas and Louisiana, 
grows well on salty prairie sites; also grows on salt marshes if 
water level is relatively low. 
USE AND MANAGEMENT 
Knotroot bristlegrass is grazed moderately by livestock, usually 
during spring and summer. It becomes unpalatable in fall and 
provides poor forage after maturity. When grazed for roughage, 
it should be supplemented with a mineral and protein concen- 
trate. Seed are readily eaten by birds. 
This grass is seldom abundant enough to be a key management 
species. For maximum production, no more than 50 percent of 
current year’s growth by weight should be removed during grow- 
ing season. Summer grazing deferments of at least 90 days every 
2 to 3 years improve plant vigor. This grass can withstand con- 
trolled burning if done after September. 
153 
