Hoary vervain is a vigorous, clump-forming perennial growing from a root system with a central taproot. It is drought and herbivore resistant. The upright flower stalk is packed with small blue to purple tubular flowers. The oval-shaped leaves are covered with hairs; hence the common name “hoary” vervain. It blooms for a long time, usually over a month. The flowers of hoary vervain are a source of nectar for many insects.