Johnsongrass
Johnsongrass
[Sorghum halapense (L.) Pers,
Poaceae (Grass Family)
▲ ▼ young plants from root sprouts
◄ mature plants
mature plants ▲
▲ ▼ inflorescences
▲ inflorescence
▲ inflorescence
▲ characteristic wide leaf blades with white midvein
▲ rhizome initiation at base of shoot
▲ ▼ shoot with rhizome
Johnsongrass: (pp. 470-471, Weeds of the Great Plains; pp. 86-87, Weeds of the Northeast)
- a noxious warm-season, creeping perennial grass weed in Missouri
- introduced as a forage in Selma, AL in 1840 by Co. Wm. Johnson
- produces 10 bushels of seed/A in large reddish or golden panicle inflorescence
- leaves fairly broad, with obvious white midvein
- seedlings will initiate rhizomes at the 7 leaf stage (about midseason of their first year)
- rhizomes allow spread into other areas
- 90% of rhizome development occurs after flowering
- rhizomes will begin growth & producing new shoots when soil temp >60° F (May-June)
- seedlings germinate at 70° F soil temperature, about 1 month later
- prefers moist, fertile soils
- occurs primarily in southern half of U.S.; winterkills further north
- can rapidly overtake entire fields without control practices