Hoary Vervain is a native erect annual to short-lived perennial forb that grows on stout, square stems, up to 3+ feet tall. The stems are green to reddish purple, dusty looking with long whitish hairs, hence the common name.
Leaves are opposite, oval to elliptical with sharp coarse teeth, a pointed tip and a narrowed base ending in a short stalk. Leaf veins are prominent. The lower leaf surface will usually have fine whitish hair.
The inflorescence is a few tall spikes branching from the top of the main stem.
The individual flowers are quite small, 1/8 to 1/4 inch wide, 5-parted, and open individually on the densely packed spike from bottom to top with only a few open at one time on each spike. Flowers have blue to purplish corolla tube, hairy on the outside, whose upper lobes form 5 oblong petals that flare outward and sometimes have a notch at the rounded tip. Between the flowers on the spike are green leafy hairy bracts that are almost as long as the flower corolla. There are 4 stamens - 2 pairs of unequal length - with yellow anthers, and a green style, all not exserted from the corolla. The calyx of the flower is of a darker purplish color, 5-lobed and quite hairy.
Seed: Fertile flowers produce a 4-chambered dry nutlet, about 4 mm long, that contains 4 very small oblong (2 to 3 mm) reddish brown seeds. These remain on the stem until shaken loose by the wind. Seeds are light, about 28,000 per ounce. They require light and 60 days of cold stratification to break dormancy.
Habitat: Hoary Vervain prefers full sun in dry to moderate moisture sites such as disturbed areas, prairies, sandy fields - a more dry environment than the other two species noted here. The root system has a taproot and the plant normally spreads by reseeding.
Names: 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. The genus Verbena was the Roman name for altar plants in general and in particular V. officinalis. The species name, stricta, refers the erect or rigid stem. The author name for the plant classification - ‘Vent.’ is for Étienne Pierre Ventenat (1757-1808), French botanist who published several works about plants in French gardens including the rare plants of Malmaison. French gardens grew many species imported from the New World.
Comparison: The differences between this plant and Blue Vervain, V. hastata, are that V. hastata has lance shaped leaves with an outward facing basal lobe and only fine hair, if any, on the stem. The flowers are similar. The White Vervain, V. urticifolia, has very small white flowers but the inflorescence is much different, being a loosely spreading panicle of many flower spikes.
Above: 1st photo - The tall flower spikes, fewer than on Blue Vervain. 2nd photo - The small blue flowers open from bottom to top on the spike with only a few open at one time. Note the narrow leafy bracts between flowers. 3rd photo - The long whitish hairs on the stems, from which is derived the common name.
Below: The calyx and lower section of the corolla tube are of a darker purplish color and quite hairy. Note the short hair on the outside of the corolla lobes.
Below: 1st photo - An individual flower of Hoary Vervain. 2nd photo - The elliptical shaped leaf of Hoary Vervain
Below: 1st photo - A lower leaf with a typical short stalk. 2nd photo - The underside has fine hair on all surfaces.
Notes: Hoary Vervain was first noted in Eloise Butler's Garden log on July 1, 1914 when she noted the plant in bloom. She planted it in 1918 and 1919. Martha Crone reported planting it in 1933. It was listed on her 1951 Garden Census. It was not on the 1986 Garden census, but is now listed once again on the 2009 Census. In North America it is somewhat more restricted in range than Blue Vervain. There are 10 states in the west, south and east where it is not found and it is reported in a few of the lower Canadian provinces of the east. Likewise in Minnesota, its range is mostly restricted to the lower half of the state - an area of drier ground which the plant prefers.
Eloise Butler wrote: The Blue Vervain [Hoary vervain], a weed common in neglected, vacant lots, is well worthy of attention. It stands up bravely among ignoble surroundings, old tins, broken bottles and ash heaps, which it attempts to mask. Large, downy leaves thickly clothe the stem. The flower spikes are long and slender, having close rows of seed pods at the base with a ring of bright blue flowers above and tapering at the tip with the still unopened buds. The garden Verbena, unlike this weed, has the lazy habit of lying with its elbows on the ground and getting covered with dirt. Published July 23, 1911
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.
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.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"