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Purpletop vervain flowers occur in dense, flat-topped clusters 1-3" across. Individual flowers are about 1/4" (5-6 mm) long and 8-9 mm long. The flowers contain a short, tubular, hairy calyx with five teeth; a pinkish purple, tubular corolla with five spreading lobes that have notched tips; four stamens which do not extend beyond the throat of the flower; and a pistil with a single style. The fruit is four nutlets, cupped in the remnants of the calyx as they mature.

Verbena

Verbena bonariensis

purpletop vervain [Blooms: Sept]

Prostrate vervain stems produce dense spikes of flowers at their tips. Beneath each flower is a 3/4" long, narrow bract with long, whitish hairs; the bracts make up the erect or sprawling flower spike (6" long, 3/4" across), with blooming flowers at the tip and fruits maturing below. Individual flowers are about 1/8" across, with a narrow, very hairy, basal calyx extending into five sharply pointed lobes, and a narrow, tubular corolla that abruptly flares into five rounded lobes ("petals") surrounding a white or greenish-white throat; the upper two lobes are slightly smaller than the lower three. Both the calyx and corolla are the same color whether light blue, purple, or pink. Hidden in the throat of the corolla are four stamens with yellow anthers and a short style. The fruit consists of a capsule containing four nutlets that is nestled in the remains of the calyx. This plant is a pioneer in highly degraded habitats that is especially fond of cracks and crevices — despite its weedy appearance, prostrate vervain is a native species. In spite of the tiny size of its anatomical characters, this is a relatively straightforward plant to confidently identify from the hairy stems, leaves, and flower spikes and the tiny, lavender apical flowers.

Verbena

Verbena bracteata

prostrate vervain [Blooms: Jun-Aug]

Flower spikes about 5" long cover the top of the blue vervain plants; they are densely covered with floral buds and flowers that bloom from the bottom of the spikes sequentially to the top. Below the open flowers are maturing fruits. Individual flowers are tubular, 1/4" long and across, with a grayish green to dark red, hairy calyx sporting five narrow teeth; a tubular, purplish-blue corolla twice the length of the calyx that abruptly flares into five equal, ovate lobes ("petals"); four recessed stamens; and a single, short style. The throat of the flower is "bearded" (occluded by light blue filaments extending to the middle of the opening) which hides the reproductive organs. This is the only vervain with a blue (not deep violet/lavender) color; other species are pink, white, or lavender. The fruit consists of four 2 mm long nutlets held in the remnants of the calyx. Blue vervain might be confused with hoary vervain, but the latter has larger (2x), lavender (not purplish-blue) flowers (with one lobe/petal notched and two larger than the other three), and ovate to egg-shaped (not lance-shaped) leaves that are sessile (not on petioles 1/2" long or longer). Blue vervain is especially common along the margins of the lagoons of Jackson Park.

Verbena

Verbena hastata

blue vervain [Blooms: Jul-Sep]

Hoary vervain flower spikes are 1-8" long; they are crowded with buds and bluish violet to lavender flowers 1/2" across that open sequentially from the bottom of the spike to the top; below the open flowers are maturing fruits. Individual flowers are tubular, 1/2" long and across, with a grayish green to reddish-purple, hairy calyx sporting five narrow teeth. The tubular, bluish violet to lavender corolla, twice the length of the calyx, abruptly flares into five ovate lobes ("petals"); the two lateral lobes are the largest, while the lower lobe(s) has/have a notched tip. Hidden in the tubular corolla are four recessed stamens with yellow anthers and a single, short green style. The fruits consist of four nutlets held in the remnants of the calyx.

Verbena

Verbena stricta

hoary vervain [Blooms: Jun-Jul]

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]