This species bears dome-shaped flower heads several inches across that are crowded with tiny, tubular amethyst or white flowers that look somewhat like the blooms of an allium. It has lance-shaped, toothed leaves in hues of cordovan purple or deep green brushed with plum highlights. It blooms over a long season. Though it is a perennial, blue throatwort performs wonderfully as an annual and blooms summer to fall. Plants grow to about 3 feet tall and wide.