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White vervain produces numerous 6" long, widely spaced flower spikes, each covered by tiny (1/8" wide) white flowers sparsely distributed along the length of the flower spike. Individual flowers consist of a hairy, tubular green calyx with five lance-like teeth and a curved, tubular corolla that abruptly flares into five short, rounded, brilliant-white lobes ("petals"). The throat of the flower is "bearded" (occluded by white filaments extending to the middle of the opening), hiding four stamens with greenish anthers, a green style, and a two-lobed stigma. The upper (more apical) two lobes of the corolla are slightly smaller than the other three (like prostrate vervain) and the tip of the lowermost lobe of the corolla is notched (like hoary vervain), but you're not likely to confuse white vervain with any other Verbena. The fruit is four oblong nutlets nestled in the remnants of the calyx.

Verbena

Verbena urticifolia

white vervain [Blooms: Jun-Sep]