Flower:

1 to 3 slender spikes, blooming from the bottom up, elongating with maturity and fruit forming below the open flowers. Flowers are about ¼ inch across, white to lavender, 5 petals nearly equal in size, fused near the base into a short tube, hairy on the outer surface and around the mouth of the tube. Inside the tube are 5 stamens and a 2-parted style. The calyx cupping the flower is slightly shorter than the floral tube, with 5 short teeth and is slightly hairy. At the base of the calyx is a green bract about as long as the calyx.

Leaves and stems:

Leaves are opposite, 1 to 4 inches long, 1/8 to about ½ inch wide, linear-oblong to spatula-shaped, widest at or above the middle, toothed at least on the upper half, hairless to sparsely hairy, blunt to pointed at the tip, tapered to the base, and stalkless or nearly so. Stems are erect, single or a few from the base, 4-sided, usually sparsely hairy, unbranched or few branched on the upper stem, the branches erect to ascending.

Fruit:

Fruit is a set of 4 brown, linear-oblong nutlets up to 3mm long, the calyx forming a capsule-like structure.

Notes:

Narrow-leaved Vervain reaches the northern edge of its range in Minnesota and has only been found in a few locations in dry prairies and rock outcrops. Elsewhere in its range it may also be found in rocky, open woods, glades, gravelly roadsides and along railroads, often where limestone is exposed or near the surface. According to the DNR, it was listed as a Special Concern species in 1984 due to its rarity, but not enough is known about its habitat requirements in the state to determine conservation strategies. It is currently also a Special Concern species in Wisconsin. While the flowering spikes are similar to other Verbena species, the relatively short stature (usually under 2 feet tall), sparsely hairy, narrow and essentially stalkless leaves, 1 to 3 spikes per stem, and tiny flowers distinguish it from the rest.