Description: This native wildflower is
an annual, biennial, or short-lived perennial about 3-6' tall; it branches
occasionally in the upper half. The central stem is light green, stout,
4-angled, and densely covered with long spreading hairs. Along its length are
pairs of opposite leaves up to 6" long and 2¼" across; they are
lanceolate to ovate and coarsely serrated along their margins. The upper
surface of each leaf is medium to dark green, shiny, hairless to slightly
hairy, and wrinkled along the veins; its lower surface is light green and more
hairy. The petioles of the leaves are up to 2" long. The central stem
terminates in a panicle of floral spikes up to 2' long and half as much across;
the upper side stems also terminate in such panicles, although they are smaller
in size. Each panicle has narrow ascending branches (up to 6" long) and an airy
appearance; sessile small flowers are sparsely distributed along each of these
branches. Each flower is 1/8" across, consisting of a white corolla with 5
rounded lobes and a tubular green calyx with 5 lanceolate teeth. The blooming
period occurs from mid-summer to early fall and lasts about 1½ months.
Only a few flowers bloom at the same time. Each flower is replaced by 4 nutlets
that are oblongoid and flattened. This wildflower reproduces by reseeding
itself.
Cultivation: The preference
is partial sun, moist to mesic conditions, and a fertile loam.
Range & Habitat: White Vervain occurs in every
county of Illinois and is quite common (see
Distribution
Map). Habitats include disturbed woodlands, woodland borders, thickets,
powerline clearances in wooded areas, semi-shaded areas along paths, damp
meadows along streams, gravelly seeps, and abandoned fields. This species is
usually found in habitats with a history of disturbance. It is somewhat
weedy.
Faunal
Associations: The nectar and pollen of the flowers attract
long-tongued bees (honeybees, bumblebees, Little Carpenter bees, Cuckoo bees,
Digger bees, & Large Leaf-Cutting bees), short-tongued bees (Halictid bees,
& Dagger bees, including Calliopsis verbenae), various flies
(Syrphid flies, Bee flies, Thick-Headed flies, & Tachinid flies), small
butterflies, and wasps. These insects cross-pollinate the flowers. Insects that
feed on the foliage of White Vervain and similar Verbena spp. (Vervains)
include Crambodes talidiformis (Verbena Moth), Longitarsus
suspectus (Flea Beetle sp.), and Macrosiphum verbenae (Verbena
Aphid). The seeds are eaten occasionally by various granivorous songbirds,
including the Slate-Colored Junco, Field Sparrow, Song Sparrow, Swamp Sparrow,
Tree Sparrow, and White-Crowned Sparrow. In contrast, the bitter coarse foliage
is rarely used as a food source by White-Tailed Deer and other mammalian
herbivores.
Photographic Location:
Along a path in Busey Woods at Urbana, Illinois. Only a small portion of the
inflorescence is revealed by the upper photograph.
Comments: Considering the large size of this plant,
its flowers are remarkably small. The scientific name refers to the resemblance
of the leaves to those of Ulmus spp. (Elms). White Vervain resembles two
of its relatives, Verbena hastata (Blue Vervain) and Verbena
officinalis (European Vervain). Blue Vervain has more narrow leaves and its
flowers are conspicuously blue, rather than bright white. It is found in sunny
wetland habitats more often than White Vervain. European Vervain has small
flowers that are white or lavender. It differs from White Vervain primarily by
its pinnatifid leaves, which have cleft lobes.