Weed Department
Idaho State Noxious 
Weed Law


General Description: Johnsongrass is a tall, upright, perennial grass, reaching 3 to 10 feet tall in height with an extensive system of rhizomes.

Flower Description: Flowers clusters (spikelets) in a branching pyramidal cluster (panicle) up to 16 inches. Spikelets grow in pairs at the lower end of this flowering stalk while spikelets are in threes at the upper end. Male and female spikelets appear on the same plant.

Leaf Description: The leaves are alternate, from 12 to 30 inches long and ½ to 1 inch wide. It has a noticeable white mid-vein.

Stem Description: Stems terminate in a reddish inflorescence.


Interesting Facts:

It is considered a weed in all annual agricultural crops, orchards, vineyards, ditches, roadsides and fence rows. When it is under stress, it produces hydrocyanic acid which is toxic to grazing livestock.