Schoenoplectus acutus
hardstem bulrush [Blooms: Jun-Jul]
Hardstem bulrush (Schoenoplectus acutus) inflorescence and spikelets. Top: the inflorescence of hardstem bulrush and its basal bract (arrow). The clusters of spikelets (“pseudoumbels”) contain two to eight spikelets. Bottom: a close-up of a hardstem bulrush cluster of spikelets with the basal bract (arrow) of the inflorescence. The hairy-looking brown threads are spent stamens, withering before they drop off.
Hardstem bulrush’s inflorescence is a branching cluster (a “pseudoumbel”) at the top of the stem with an erect bract at its base that is C-shaped in section and 3/8-3.5″ long; the bract appears to be a continuation of the stem. The clusters (“pseudoumbels”) may be open or compact, but are more compact than in softstem bulrush. There may be 3-40 spikelets, some solitary (but never all solitary), some in groups of 2-8 at the tips of stiff floral stalks. The spikelets are reddish-brown, 10-17 mm long, cylindrical or spindle-shaped with pointed tips and with 8+ florets spirally arranged on the spikelet. The florets are perfect (both male and female parts present), each with three stamens and a two-part style; each floret is subtended by a single, 3 mm long, red-spotted scale, often with a contorted awn (both of which may be difficult to see — magnification recommended). Hardstem bulrush can tolerate standing water as much as five feet deep. You are most likely to confuse hardstem bulrush and softstem bulrush. The stem in softstem bulrush (Schoenoplectus tabernaemontani) is spongy to the touch and the pith has numerous much larger air cavities than hardstem bulrush in most of the pith. Softstem bulrush has mostly solitary spikelets, a much more open inflorescence, scales covering the florets that are usually not red-spotted, and is a lighter blue green color than hardstem bulrush’s dark olive green. Softstem bulrush is much more common in Jackson Park than is hardstem bulrush.
Hardstem bulrush (Schoenoplectus acutus) stems. The main image shows the basal regions of a stand of hardstem bulrush; the leaves are few (3-4) and largely hidden by the leaf sheaths. The odd structure in the lower left hand corner is the top of a scouring rush or horsetail (Equisetum hyemale) with a cone-like strobilus at its tip that produces the plant’s spores. The image in the lower right corner is of a cross section of a hardstem bulrush’s stem, showing the white pith.
Hardstem bulrush is a towering native perennial, an emergent aquatic that can be 3-10 feet tall. (Six feet is common.) The stems are erect, round in section, a dark olive green, and firm (not spongy) when gently squeezed. (Thus, the common name.) If the stem is cut across, the pith contains numerous, uniform (0.5 mm) air cavities. There are only three or four leaves, all basal; only one or two may have a blade longer than the leaf sheath.
A stand of hardstem bulrush (Schoenoplectus acutus) on the south shore of 59th St. Harbor.
Hardstem bulrush is a towering native perennial, an emergent aquatic that can be 3-10 feet tall. (Six feet is common.) The stems are erect, round in section, a dark olive green, and firm (not spongy) when gently squeezed. (Thus, the common name.) If the stem is cut across, the pith contains numerous, uniform (0.5 mm) air cavities. There are only three or four leaves, all basal; only one or two may have a blade longer than the leaf sheath. The inflorescence is a branching cluster (a “pseudoumbel”) at the top of the stem with an erect bract at its base that is C-shaped in section and 3/8-3.5″ long; the bract appears to be a continuation of the stem. The clusters (“pseudoumbels”) may be open or compact, but are more compact than in softstem bulrush. There may be 3-40 spikelets, some solitary (but never all solitary), some in groups of 2-8 at the tips of stiff floral stalks. The spikelets are reddish-brown, 10-17 mm long, cylindrical or spindle-shaped with pointed tips and with 8+ florets spirally arranged on the spikelet. The florets are perfect (both male and female parts present), each with three stamens and a two-part style; each floret is subtended by a single, 3 mm long, red-spotted scale, often with a contorted awn (both of which may be difficult to see — magnification recommended). Hardstem bulrush can tolerate standing water as much as five feet deep. You are most likely to confuse hardstem bulrush and softstem bulrush. The stem in softstem bulrush (Schoenoplectus tabernaemontani) is spongy to the touch and the pith has numerous much larger air cavities than hardstem bulrush in most of the pith. Softstem bulrush has mostly solitary spikelets, a much more open inflorescence, scales covering the florets that are usually not red-spotted, and is a lighter blue green color than hardstem bulrush’s dark olive green. Softstem bulrush is much more common in Jackson Park than is hardstem bulrush.
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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)
