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 exerted 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.
Above: 1st photo - Note that branching occurs only near the top of the stem. 2nd photo - The individual flowers open from the bottom to the top of the spike.
Below: 1st photo - The individual flowers form 5 outward spreading lobes from the corolla. The reproductive parts are all enclosed in the corolla tube. 2nd photo - The calyx of the flower tube is hairy with five pointed lobes that have violet tips.
Below: The lance shape lower leaf with the outward facing base lobes - from this leaf design like the halberd of a sword comes the species name hastata.
Below: 1st photo - a smaller upper leaf with its short stalk. Intricate vein pattern. 2nd photo - The underside is paler color with many fine hair, especially on the veins and ribs.
Below: The seed pods are 4-angled and only 4mm long, each containing 4 of the brown oblong 4-sided 2mm long seeds.
Notes: Blue Vervain is indigenous to the Garden; Eloise Butler catalogued it on Sept, 6, 1907. Martha Crone listed it on her 1951 Garden Census. It is found throughout the lower 48 states and in the lower Canadian Provinces except Alberta. In Minnesota it is native to and has been found in most counties throughout the state with only a few scattered exceptions, one metro exception being Dakota County.
There are 5 Verbenas found today in Minnesota, 4 native and 1 introduction. Also 3 other species that are known historically only, with some question as to whether they ever were found here. The extant Verbenas are: V. hastata, Blue or Swamp Vervain; V. simplex, Narrow-leaved Vervain; V. stricta, Hoary Vervain; V. urticifolia, White Vervain; and V. bracteata, Large-bracted Vervain. The latter is the introduction. V. simplex is on the state's Special Concern List.
Lore: Mrs. Grieve (Ref. #7) states that the name vervain is derived from the Celtic ferfaen, that is from fer (to drive away) and from faen (a stone). In early times the plant was used for afflictions of the bladder. Verbena was the Roman name for altar plants in general and in particular V. officinalis. She also lists many medicinal uses. Densmore (Ref. #5) in her study of the Minnesota Chippewa reports their usage of the dried flowers as "snuffed" to cure nosebleed. Recent research has shown that using Blue Vervain for medicinal purposes can interfere with blood pressure medicines and hormone therapies. (Ref. #W2)
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"