Johnsongrass-SeedlingJohnsongrass-Seed HeadJohnsongrass_3D54[1]

(Sorghum halepense)

Erect, perennial, rhizomatous, warm-season grass.
Ranked among the top ten world's worst weeds

Distinguished from other grasses by:
            *Ribbed leaf sheath
            *Leaves have conspicuous midrib
            *Large, purplish, panicled seed head
            *Extensive large, fleshy, purple rhizomes

            *Fertile, porous soils, pH 5.0-7.5
            *Disturbed, flooded lands
            *Ditches and waterways
            *Cultivated fields

            *Flowering occurs approximately 8 weeks after emergence in spring
            *Exact time of flowering depends on temperature, plant vigor and photoperiod (8-16 hours)

            *Primary spring growth is from apical and axillary nodes
            *Secondary growth is annual above and below ground structures
            *Rhizome spurs and tillers initiate growth 30 days after onset of primary growth, usually at six leaf 
            *Majority of rhizome growth occurs after flowering
            *Minimum temperature of rhizome growth is 59 degrees
            *Rhizome depth depends on soil type, shallow in clay-deeper in loam, average is 8

            *Dispersal mechanisms: contaminated feed and forage, livestock, machinery, water and wind.

Growth and reproduction:
            *Plants can regenerate from small rhizome fragments (2")
            *Most seeds germinate during second year
            *Carbohydrate reserves are lowest in early spring and early fall, and are at the absolute lowest 
             10-30 days after flowering

            *Constant cultivation to chop, desiccate and/or freeze rhizomes
            *Frequent mowing to deplete carbohydrate reserves
            *Herbicides: glyphosate, imazapic

            *Rapid growth and height shades smaller plants
            *Aggressively competes for light, nutrients and water
            *Stress can produce hydrocyanic acid, cured hay ok
            *Johnsongrass serves as host for crop diseases
            *Highly allergenic due to the amount of pollen produced