white vervain

Great Plains

Midwest

FAC - Facultative

Northcentral & Northeast

FAC - Facultative

Native

Common

Moist to moderately moist. Woodland borders and openings, thickets, power lines, trails, disturbed sites. Partial sun.

June to October

White

20″ to 60″

This is an annual, biennial, or short-lived perennial forb. It rises on a single stem.

The stems are erect, slender, 20″ to 60″ tall, moderately to strongly four-angled, and usually branched near the base. They are moderately to densely covered with spreading, straight or somewhat curved hairs.

The leaves are opposite and broadly lance-shaped to oblong egg-shaped. They are mostly2″ to 4¾″ long and ¾″ to 2¾″ wide, but larger leaves may be up to 8″ long and 4¾″ wide. They are on ½″ to 2″ long leaf stalks (petioles) that are usually winged above the middle. The blades are unlobed, rounded or short tapered at the base, and tapered to a sharp point at the tip. They do not clasp the stem. The lower is densely velvety, covered with 1⁄64″ long hairs. The margins are somewhat coarsely and sometimes doubly toothed.

The inflorescence is a very loosely spreading branched cluster (panicle) of several to numerous spikes at the end of the stem and additional smaller panicles or spikes rising from the upper leaf axils. The spikes are slender, usually stiffly ascending, and 3″ to 20″ long. At first they are relatively short and crowded with buds. As the flowers bloom from the base toward the tip the spike becomes greatly elongated. Only a few flowers on each spike are in bloom at any one time. The blooming flowers do not overlap.

The flowers are about ⅛″ wide. There are 5 sepals, 5 petals, 4 stamens, and 1 style. The sepals are green, and are united at the base into a narrowly bell-shaped tube (calyx), then separated into 5 short teeth that are unequal in length. The calyx is 1 ⁄32″ to 1 ⁄16″ long when in flower, elongating to about 3 ⁄16″ long in fruit. It is covered with soft, minute hairs that are barely visible without magnification. The modified leaves (bracts) at the base of each flower are egg-shaped to narrowly egg-shaped and 1⁄64″ to 1 ⁄16″long. They are shorter than the calyx. The petals are white and 1 ⁄16″ to ⅛″ long. They are fused at the base into a slender, funnel-shaped tube then separated into 5 blunt, broadly triangular limbs.

Each flower produces a cluster of 4 nutlets that are enclosed in the persistent calyx but are exposed at the tip. Each nutlet is narrowly ellipse-shaped, 1 ⁄16″ long, and smooth, not corrugated on the back.

White vervain (Verbena urticifolia var. urticifolia) leaf underside is hairless or moderately covered with whitish, 1⁄32″ to 1 ⁄16″long, coarse, stiff hairs. The calyx is covered with short, sharp, stiff, appressed hairs. The nutlet is slightly longer and corrugated on the back.

Sources: 7.

Photography
This plant is difficult to photograph in its entirety. The flower spikes spread widely in all directions and the individual flowers are tiny. The inflorescence tends to get lost against the background and most of it is inevitably out of focus.

Leaves

Stem