Plants of the Eloise Butler Wildflower Garden

Blue Vervain is a native erect biennial or short-lived perennial that grows to 40 inches tall on square stems with branching near the top. Stems are green to greenish-red, with 4 angles and occasionally with fine hair.

Leaves are opposite, lance-like with coarse teeth, about 4 - 6x longer than wide, pointed tips and tapering at the base to a short stalk. Lower leaves up to seven inches long. Lower leaves will usually have a lobe at the base facing outward like the halberd of a sword handle. Upper leaves are smaller. The underside has fine whitish hair with longer hair on the main veins.

The inflorescence is a loosely branched terminal cluster with many flower spikes (a panicle). There can be auxiliary flower stalks rising from the upper leaf axils.

The individual flowers have blue to violet colored corollas (sometimes whitish) forming a tube; they are quite small, 1/8 to 1/4 inch wide, 5-parted; the calyx of the flower tube is hairy with five pointed lobes that have violet tips; and the petals have rounded lobes spreading outward when the flower opens. There are 4 stamens - 2 pairs of unequal length - with yellowish anthers, and a green style, all not exserted from the corolla. Flowers open individually on the densely packed spike from bottom to top with only a few open at one time on each spike.

Seed: Fertile flowers produce dry nutlets that are 4-sided, about 4mm long and hold very small (1.5 to 2mm) oblong reddish brown seeds. These remain on the stalk until shaken off by the wind. These nutlet pods are twice the size of those of White Vervain, V. urticifolia. Seeds are extremely small and light, about 93,000 per ounce. They need at least 30 days of cold stratification and light for germination.

Habitat: Blue Vervain is found in moist places - stream banks, pond edges, meadows and moist prairies. It requires full sun and a loamy soil. It grows from a rhizomatous root system. It is not aggressive.

Comparisons: The differences between this plant and Hoary Vervain, V. stricta, are that V. stricta has elliptical leaves and long hairs on the stem. The flowers are similar but of a different shade of color. White Vervain, V. urticifolia, has similar, but much smaller white flowers and a spreading loose inflorescence of many wildly spreading spikes.

Names: The genus name Verbena is from the Latin and now refers to the Vervain plant. Further details are listed at the bottom of the page. The species name, hastata, refers to the leaf which has a spear shape with a basal lobe that faces out like a halberd. See the photo below. The alternate common name of Swamp Vervain refers to a common habitat of this plant being stream and pond banks. See notes below on the origin of Verbena. The author name for the plant classification, 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.