Introduced. Annual. • Propagates by seeds. Time of bloom: June to September. Seed-time: July to November. Range: New England and Middle Atlantic States, southward to Florida and Texas. Also on the Pacific Coast. Habitat: Fields, roadsides, and waste places.
An escape from gardens that has become a troublesome weed in many places. Stem one to three feet tall, smooth, four-sided, slender, branched and spreading. Leaves opposite, oblong lance-shaped in outline but pinnatifid, the lower ones tapering to margined petioles; upper ones becoming nearly or quite entire and sessile. Flowers purple, very small, on slender, bracted, threadlike spikes often four or five inches long; corollas tubular, the five lobes spreading salver-form; stamens four, in two pairs of unequal length, included; calyx five-toothed, enclosing the fruit, which, as in all the Vervains, splits into four very small, hard nutlets.
Prevent seed production by close cutting or pulling while the plant is in early bloom.