Identification and Reproduction

Identification: 

• Johnsongrass is a perennial grass that grows up to 2.4 m tall. 
• Leaves are alternate, hairless, lanceolate and have a distinct white midrib. 

• Flowers are found in a loose purple panicle that can measure up to 50 cm in length. 

• Culms above ground appear bulb-like and swollen. 
• Rhizomes are fleshy, short and knotty. 

Reproduction: 

• This plant reporduces by rhizomes and seed. 
• It is a prolific seed producer. Each individual panicle produces hundreds of seeds. 
• Rhizome system is extensive and can reach to depths of 1.2 m. 
• Can resprout from fragmented rhizome parts. 
• Young plants that sprout from rhizomes grow much faster thatn seedlings. 

Habitat & Ecology

• It grows in crop fields, pastures, abandoned fields, right of ways, forest edges, streambanks and other disturbed areas. 
• Is very aggressive on exposed, rich, cultivated fields. 
• Johnsongrass is found on every continent except for Antarctica. 

Impacts

Social:

• Although edible, if an excessive amount of the foliage is consumed, it can kill cattle and horses. 
• Can also cause excessive bloating of other livestock. 
• Reduces pasture land and displaces crop species. 

Ecological:

• Grows and spreads rapidly, outcompeting and shading out native species.
• Dense rhizomatous mats prevent the establishment of trees. 
• Infestations dry and die in the summer and will be come a potential fire hazard. 

Management

Prevention is a high priority for this species. 

• Learn to identify this plant and report sightings. 
• Clean and remove any seeds that may attach to clothing, shoes, equipment and pets when leaving an infested site. 
• Refrain from moving unknown soil and plant matter. 

Mechanical/Manual Control: 

• Cutting or clipping plants close to the ground regularly, bi-weekly or monthly between spring and winter will significantly decrease the plants growth. 
• Regular mowing also helps deplete the energy supply of the rhizomes and helps weaken the plants. Seedlings that sprout the following year should be reduced greatly. 
• Hand hoeing is effective on small populations of Johnsongrass. It is most successful in the spring when plants are young and rhizomes have not established deep into the soil. 

Resources

For more information check out the Bugwood Wiki datasheet on Sorghum halepense. 

Header photo (Hillebrand Steve).