A native North American plant, occurring in nearly every state in the United States, and into Canada and Mexico.
A biennial or perennial plant whose foliage generally dies back in the winter and re-grows from the roots in the warm season. Reproduction is from seeds.
Plants are erect and very tall, on long thin stems up to 4 feet in height. Leaves are opposite and elongate lance-shaped with pointed tips. Their margins are strongly toothed and they have short petioles. The flowering heads are spikes about ½ inch long, crowded with the bluish to purple, small flowers. The top of the stem branches several times to accommodate several flower spikes in an open grouping.
Characteristicts Important to Control:
Generally a minor problem, but where it is not wanted it can be effectively controlled with a systemic herbicide.