Vervain, belonging to the genus Verbena, is a widely recognized group of herbs often encountered in wild and disturbed landscapes. These plants are identified by their upright, somewhat wiry appearance, which helps them stand out among other field flora. This guide provides a clear visual breakdown of the features necessary to correctly identify this common perennial.
Overall Plant Structure and Habitat
Vervain species generally display an erect, somewhat scraggly growth habit, often appearing tall and thin rather than bushy. The typical height of the plant can vary significantly, with Common Vervain (Verbena officinalis) reaching up to about three feet, while the North American Blue Vervain (Verbena hastata) can stand between two and six feet tall. Most vervains are short-lived perennials, meaning they persist for a few years, but they readily self-seed to ensure their continued presence in an area.
These herbs are frequently found in open, sunny locations, thriving in a variety of soils, including rough ground, waste areas, and dry grasslands. Some species, like Blue Vervain, prefer moist to wet conditions, often colonizing stream banks and wet meadows. The plant’s overall silhouette is characterized by its stiff, vertical stems that branch near the top to form a candelabra-like structure.
Distinctive Features of Leaves and Stems
A defining characteristic of many vervain species is the appearance and texture of the stem, which is often square or noticeably ridged and sometimes exhibits a reddish tinge. The stems are typically covered in sparse, fine hairs, contributing to a slightly rough feel. This angular stem profile is a useful identification clue when the plant is not in flower.
The leaves of vervain are arranged oppositely along the stem, with the specific shape varying depending on the species. Common Vervain leaves are often deeply cut or lobed, especially the lower ones, giving them a lacy or feathery look. Upper leaves tend to be smaller and less divided, sometimes only having toothed edges.
The foliage is often a medium or grey-green. Blue Vervain leaves, for instance, are lance-shaped, coarsely toothed, and can be up to six inches long, attaching to the stem via a short stalk or petiole. Leaf shape and attachment are key factors in distinguishing between different species.
Flower Spikes and Seed Formation
The most distinct identification feature of vervain is the appearance of its flower spikes, which are long, slender, and numerous, rising above the main foliage. These spikes form a loose, branched cluster at the top of the plant, often described as a panicle shape. Individual flowers are very small, measuring only about one-eighth to one-quarter of an inch across.
Each tiny flower has five lobes and a tubular base, and they are densely packed along the spike. The blooms open sequentially from the bottom of the spike upwards, meaning only a few flowers are open at any one time, which prolongs the overall flowering period. Flower colors are typically delicate shades of blue, purple, lilac, or white, creating a subtle but persistent display from mid-summer into early fall.
Following pollination, the small flowers are replaced by tiny, dry fruits known as schizocarps, which split into four small nutlets. These nutlets are oblong, four-sided, and typically reddish-brown, remaining nestled within the dried calyx. The entire flower spike gradually turns brown and dries out as the seeds mature, often remaining on the stem until shaken loose.
Key Varieties and Their Differences
The term “vervain” refers to several species, and recognizing the differences among the most common types aids in precise identification. Common Vervain (Verbena officinalis) is generally a shorter plant, typically under three feet, and features very slender flower spikes with pale lilac or pinky-white flowers. Its lower leaves are deeply dissected, while the upper leaves are more simple and toothed.
In contrast, Blue Vervain (Verbena hastata) is a taller North American native, commonly reaching five feet or more, and prefers moister soil conditions. Its flowers are a more distinct blue or violet-purple, and its leaves are distinctly lance-shaped with coarse teeth, often having a short stalk. Hoary Vervain (Verbena stricta) is another variety, distinguished by its broader, oval leaves that are attached directly to the stem without a stalk, and it thrives in drier habitats.
The flower spikes of Blue Vervain are more densely packed than those of Common Vervain, creating a more pronounced, torch-like appearance. Although all species share characteristic opposite leaves and small, five-lobed flowers, the combination of height, flower color, and leaf structure are the visual cues used to differentiate them.