Blue vervain sends up candelabras of slender flower spikes in midsummer, each one opening a ring of small violet-purple flowers that moves slowly up the spike over weeks. Verbena hastata is a native perennial growing 2 to 5 feet tall and 1 to 3 feet wide in full sun, hardy from Zone 3 through Zone 9.
Butterflies and bees come to the flowers in numbers through the long bloom, and it is a nectar source at a point in summer when a lot of things have finished. Songbirds take the seed in fall.
The stems are square and stiff, and the whole plant stands upright without staking even at five feet.
Blue vervain grows wild in wet meadows, ditches, and along stream edges, so it takes wet ground and wants consistent moisture. It struggles in a dry bed. It self-sows freely, which suits a rain garden, a meadow, or a naturalized planting rather than a formal bed. Deer leave it alone.