white vervain

not listed

NNR - Unranked

SNR - Unranked

not listed

FAC - Facultative

FAC - Facultative

FAC - Facultative

White vervain is an annual, biennial, or short-lived perennial forb. It rises one to several stems.

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 surface is hairless or moderately covered with whitish, 1⁄32″ to 1 ⁄16″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 hairy and 1 ⁄32″ to 1 ⁄16″ long when in flower, elongating to about 3 ⁄16″ long in fruit. The hairs on the calyx and on the underside of the leaves may be soft and velvety, or short, sharp, stiff, and appressed. 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, 5 ⁄64″ long, and smooth, corrugated, or ribbed on the back.

20″ to 60″

White

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

June to October

Sources

2, 3, 4, 5, 7, 24, 28, 29, 30.

Native

Common

There are two generally recognized varieties. On var. leiocarpa, the hairs on the underside of the leaves and on the calyx are softer, and the nutlet is shorter and smooth on the back. On var. urticifolia, the hairs are stiff and appressed, and the nutlet is shorter and ribbed on the back. The two ranges overlap extensively, and the variteies intergrade freely where they overlap. For these reasons, most authors do not recognize the varieties.

Plant

Leaves

Stem

Location: Cass County