Verbena hastata
blue vervain [Blooms: Jul-Sep]
Blue vervain (Verbena hastata) flowers. Bottom right: the candelabra-like flower spikes of blue vervain. Top right: close-up of blue vervain flowers. Note the blue (not violet or lavender) petals, five petals all the same size, and the throat of the flower occluded by blue hairs. Top left: further magnifying blue vervain flowers. On two of the flowers (center left and center right) you can clearly see their tubular nature. Bottom left: blue vervain flower spikes with a bumblebee for scale.
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 (twice as large), 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.
Blue vervain (Verbena hastata) stems and leaves. Top left: a four-angled (square) stem of blue vervain with two pairs of opposite upper stem leaves attached. Bottom left: basal leaves from two different blue vervain plants. The basal leaves are lance-shaped with sharply pointed basal lobes; overall they are reminiscent of a halberd. Right: two upper stem leaves from blue vervain. In each pair of images, the upper image is of the upper surface of the leaf and lower image is of the underside of the same leaf. The lower pair of images is of a stem leaf growing lower on the stem; note the small but distinct pairs of sharply pointed basal lobes and compare them with the images on the lower left.
Blue vervain (aka, swamp vervain) is a native perennial up to five feet tall with occasional branches in the upper half but is a very spare plant (except for the delicate candelabras of blue flowers). The stems are green to reddish, square in section (four-angled), sometimes covered with appressed, white hairs. The leaves are opposite, light- to medium-green, lance-shaped, six times longer than wide, with 1/2-1″ long petioles, prominent veins, and coarsely serrated margins; the lower leaves are three-lobed and rather halberd-shaped.
Two blue vervain (Verbena hastata) plants, one growing on the east shore of East Lagoon (left) and the other growing in Bobolink Meadow (right).
Blue vervain (aka, swamp vervain) is a native perennial up to five feet tall with occasional branches in the upper half but is a very spare plant (except for the delicate candelabras of blue flowers). The stems are green to reddish, square in section (four-angled), sometimes covered with appressed, white hairs. The leaves are opposite, light- to medium-green, lance-shaped, six times longer than wide, with 1/2-1″ long petioles, prominent veins, and coarsely serrated margins; the lower leaves are three-lobed and rather halberd-shaped. Flower spikes about 5″ long cover the top of the plant; 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.
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![Evening primrose — clusters of yellow flowers occur at the apex of the plant. The flowers are 1-2" across, with four 1/2-1" long green sepals strongly reflected over a long (3/4-2"), green, cylindrical floral tube (the ovary is located just above the leaf axil), four heart-shaped yellow petals, eight stamens, and a single style with an X-shaped stigma. The sepals typically remain connected (in pairs) along one edge until the flower opens. The seedpods develop within the ovary (the base of the elongate floral tube); they are hairy, urn-shaped with rounded edges, and have four or eight small lobes on the apex. The seeds are claimed to remain viable in the soil for up to 70 years. The flowers open at dusk and close early in the day. — — — There are (at least) three evening primroses in Jackson Park — common evening primrose (Oenothera biennis), northern evening primrose (Oenothera parviflora), and hairy evening primrose (Oenothera villosa). They are easily confused with each other. (Judging by the conflicts between the accounts on Illinois Wildflowers [https://www.illinoiswildflowers.info/], Minnesota Wildflowers [https://www.minnesotawildflowers.info/], and Missouri Plants [http://www.missouriplants.com/], even the experts are confused.) All three species have yellow flowers with an X-shaped stigma, reflected sepals, petals with a small notch in their apex, stems that may be red or green, and lance-shaped leaves with short, widely-spaced teeth. Northern evening primrose is distinguished by (1) the presence of a knob or ridge at the tip of each sepal which the other two species lack (2) a seed capsule with four robust, flaring lobes with rounded tips at the apex of the seed capsule, and (3) a stigma that is very robust and almost fills the opening of the flower. Northern evening primrose has green to yellowish-green sepals. Hairy evening primrose (often but not always) has (1) striped or reddish-tinged sepals (check the buds where this character is often easier to see), (2) flowers that turn orange as they begin to senesce (although the reliability of this character is uncertain), and (3) always has glandular hairs covering the ovary that have "pimple-like" bright-red bases; these red pimples may also occur on the stems. All three species are somewhat similar to prairie sundrop (O. pilosella); the latter has very hairy stems and leaves, and translucent lines that radiate from the base of the petals in the flowers.](https://jacksonparkwildflowers.info/wp-content/uploads/2025/03/Oenothera_biennis-1t-300x300.jpg)
![Northern evening primrose flowers are 3/4-1.5" across, have four yellow, heart-shaped petals, eight yellow stamens, and a cross-shaped stigma on a modest style; the stamens are as long or longer than the petals and the stigma is nearly fills the floral opening. At the base of the flower are four sepals 1/2-1" long, that bend back along the 3/4-1.5" long floral tube as the flower develops with pairs of sepals attached along one edge until the flower opens. Only northern evening primrose with a distinct ridge or knob near the tips of the sepals. The seed capsule develops from the ovary; it is 3/4-1.5" long, cylindrical but tapering slightly towards the tip, with four robust, flaring lobes at the tip. — — — There are (at least) three evening primroses in Jackson Park — common evening primrose (Oenothera biennis), northern evening primrose (Oenothera parviflora), and hairy evening primrose (Oenothera villosa). They are easily confused with each other. (Judging by the conflicts between the accounts on Illinois Wildflowers [https://www.illinoiswildflowers.info/], Minnesota Wildflowers [https://www.minnesotawildflowers.info/], and Missouri Plants [http://www.missouriplants.com/], even the experts are confused.) All three species have yellow flowers with an X-shaped stigma, reflected sepals, petals with a small notch in their apex, stems that may be red or green, and lance-shaped leaves with short, widely-spaced teeth. Northern evening primrose is distinguished by (1) the presence of a knob or ridge at the tip of each sepal which the other two species lack (2) a seed capsule with four robust, flaring lobes with rounded tips at the apex of the seed capsule, and (3) a stigma that is very robust and almost fills the opening of the flower. Northern evening primrose has green to yellowish-green sepals and is the only one of the three evening primroses to (sometimes) have reddish color on some or all of the midvein of the leaves. Hairy evening primrose (often but not always) has (1) striped or reddish-tinged sepals (check the buds where this character is often easier to see), (2) flowers that turn orange as they begin to senesce (although the reliability of this character is uncertain), and (3) always has glandular hairs covering the ovary that have "pimple-like" bright-red bases; these red pimples may also occur on the stems. All three species are somewhat similar to prairie sundrop (O. pilosella); the latter has very hairy stems and leaves, and translucent lines that radiate from the base of the petals in the flowers.](https://jacksonparkwildflowers.info/wp-content/uploads/2025/03/Oenothera_parviflora-1t-300x300.jpg)
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