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. 86-87, Weeds of the Northeast; pp. 470-471, Weeds of the Great Plains)

·       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