Trillium recurvatum
prairie trillium [Blooms: Apr-May]
Prairie trillium (Trillium recurvatum) flowers. Top: lateral view of a single prairie trillium flower. The maroon flowers are sessile, directly attached to the top of the stem just above the attachment of the petioles of the whorl of leaves. The sepals lie just below the petals but are recurved so they lie parallel to the stem. Bottom right: unlike large-flowered trillium (Trillium grandiflorum), the leaves of prairie trillium are attached to the stem by short petioles. The recurved sepals lie between the petioles. Bottom left: the anthers are dark purple and just visible through the gaps between the petals. The styles and stigma are not visible without removing parts of the flower.
The apical flowers of prairie trillium have three green sepals that are reflexed so they point down, three maroon petals, six maroon stamens with dark purple anthers incurved toward the center of the flower, and three purple styles with divergent stigmas hidden from view by the stamens. The fruit is a green, six-angled, ovoid berry 1″ long; the seeds have an oily food appendage (an elaiosome) that encourages ants to carry them away. Despite the name, prairie trillium does not occur on prairies; it is a shade-loving, woodland plant like the other local trillium, large-flowered trillium (Trillium grandiflorum). Prairie trillium is superficially similar to toadshade (Trillium sessile), but in toadshade the sepals are spread (perpendicular to the stalk), not recurved (parallel to the stalk, pointed down). In addition, the leaves of toadshade are sessile (no petiole) and rarely have the troutlily-like mottling on the leaves that is seen on prairie trillium. The stamens of toadshade are yellow, not maroon. Toadshade does occur in Illinois, but it is not common, and I have yet to see it in Jackson Park.
Prairie trillium (Trillium recurvatum) leaves. Top: the leaves of prairie trillium lie at the top of the stem, just below the sessile, maroon flower. The leaves have short petioles that shift the leaf blades away from the flower. Bottom right: a prairie trillium flower bearing an immature bud, still covered by the sepals. Note the variegated mottling that covers the upper surface of the leaves, an unusual feature in wildflowers but also present in the (unrelated) troutlily. Bottom left: two prairie trillium growing side by side; compare the mottling on the two plants.
Prairie trillium is a native perennial with a single stem; it is a stately plant that grows to 16″ tall (including the flower). The stem is usually reddish-purple, stout, and round in section, with a whorl of three leaves at the apex, just below the sessile flower. The leaves are up to 6″ long and 3″ across, oval, with short (1/2″) but distinct petioles (i.e., the leaves are not sessile) and smooth margins. The upper surface of the leaf is mottled with light and darker green rectangular patches reminiscent of troutlily (Erythronium albidum) leaves; the underside of the leaves is a uniform pale green.
A prairie trillium (Trillium recurvatum) growing in the woods north of Bobolink Meadow in early May.
Prairie trillium is a native perennial with a single stem; it is a stately plant that grows to 16″ tall (including the flower). The stem is usually reddish-purple, stout, and round in section, with a whorl of three leaves at the apex, just below the sessile flower. The leaves are up to 6″ long and 3″ across, oval, with short (1/2″) but distinct petioles (i.e., the leaves are not sessile) and smooth margins. The upper surface of the leaf is mottled with light and darker green rectangular patches reminiscent of troutlily (Erythronium albidum) leaves; the underside of the leaves is a uniform pale green. The apical flowers have three green sepals that are reflexed so they point down, three maroon petals, six maroon stamens with dark purple anthers incurved toward the center of the flower, and three purple styles with divergent stigmas hidden from view by the stamens. The fruit is a green, six-angled, ovoid berry 1″ long; the seeds have an oily food appendage (an elaiosome) that encourages ants to carry them away. Despite the name, prairie trillium does not occur on prairies; it is a shade-loving, woodland plant like the other local trillium, large-flowered trillium (Trillium grandiflorum). Prairie trillium is superficially similar to toadshade (Trillium sessile), but in toadshade the sepals are spread (perpendicular to the stalk), not recurved (parallel to the stalk, pointed down). In addition, the leaves of toadshade are sessile (no petiole) and rarely have the troutlily-like mottling on the leaves that is seen on prairie trillium. The stamens of toadshade are yellow, not maroon. Toadshade does occur in Illinois, but it is not common, and I have yet to see it in 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)
![Hairy evening primrose produves an elongating spike of flowers arises from the apex of the stem; flowers bloom near the tip while older flowers and seed capsules develop below. Individual flowers are 3/4-1.5" across; they sit on a long floral tube with the ovary at its base (attached to a leaf axil). The flowers have four yellow, heart-shaped petals, eight yellow stamens, and a cross-shaped stigma on a modest style; at the base of the flower are four sepals 3/8-3/4" long, reflected back along the floral tube as the flower develops with pairs of sepals attached along one edge until the flower opens. The sepals are often red-striped or red-tinged. Note the long, hairy floral tube below the sepals, the reddish stem, and glandular hairs with red bases on the ovary. The seed capsule develops from the ovary; it is up to 1.75" long, cylindrical but tapering slightly towards the tip, with four tiny 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. 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_villosa-1t-300x300.jpg)
