Staphylea trifolia
bladdernut [Blooms: Apr-May]
Bladdernut (Staphylea trifolia) flowers and fruit. Bottom right: a cluster of bladdernut flowers dangling from the flower stalk. Top right: a closer view of bladdernut flowers in their natural orientation. The bright white petals are largely hidden by the greenish-white sepals; the stamens with their orange anthers and the single central style emerge from the mouth of the bell-shaped flower. Top left: three-quarters view of the mouth of a bladdernut flower. The five stamens with their orange anthers sit just behind the three-lobed stigma of the single style. Bottom left: a cluster of bladdernut fruit. The papery bladder contains multiple seeds in each internal chamber.
Bladdernut produces white, drooping, bell-shaped flowers in clusters of 5-12 from the axils of the leaves. Each flower is pendant on a long stalk, bell-shaped, about 8 mm long and about 6 mm wide. Flowers have five greenish-white sepals overlapping much of the petals, five bright white petals (visible through the gaps between the sepals) that flare at their tips, five stamens with white filaments and deep yellow-orange anthers, and a greenish-white style with a three-lobed stigma extending beyond the mouth of the bell. The flower stalks (pedicels) are about 1.5-2 times the length of the flower. The fruit is a greenish-white to brown, papery pod (like a “Chinese lantern”) that is about 3″ long and 2″ across with three lobes/chambers, pointed on their distal ends; each chamber contains up to four 1/4″ seeds. Both flowers and fruits are distinctive and easily recognizable.
Bladdernut (Staphylea trifolia) leaves. Top left, right: The leaves of bladdernut are usually trifoliate compound. The lateral leaflets are nearly sessile, the apical leaflet is borne on a stalk (petiolule) usually less than an inch long. Bottom: the upper surface (left) of a bladdernut leaf and the underside (right) of the same leaf.
Bladdernut is a native, 6-12 foot tall shrub or small tree; in Jackson Park it seems to thrive both in old woodlands and in open areas by the lagoons. Bladdernut is the only member of the family Staphyleaceae in Illinois. The trunk and larger branches have grey, rough-textured bark. Smaller branches have smooth bark with longitudinal streaks of black and light grey, while the smallest twigs are usually smooth and reddish brown. The leaves are opposite, usually trifoliate compound — thus the species name “trifolia” — with 1-5″ long petioles. (Rarely, the leaves are five-foliate compound.) The leaflets are oval, hairy on the underside, with finely serrated margins, and rounded or wedge-shaped bottoms tapering to a short, fine tip. The leaflets are up to 2.5″ long and about 1″ wide. The terminal leaflet has a petiolule (stalk) up to 1″ long; the two lateral leaflets are nearly sessile.
A bladdernut (Staphylea trifolia) shrub growing on the shore of East Lagoon on the southeast corner of Bobolink Meadow. The flowers are difficult to discern at this scale but an enlarged view of a cluster of flowers is shown in the upper left corner.
Bladdernut is a native, 6-12 foot tall shrub or small tree; in Jackson Park it seems to thrive both in old woodlands and in open areas by the lagoons. Bladdernut is the only member of the family Staphyleaceae in Illinois. The trunk and larger branches have grey, rough-textured bark. Smaller branches have smooth bark with longitudinal streaks of black and light grey, while the smallest twigs are usually smooth and reddish brown. The leaves are opposite, usually trifoliate compound — thus the species name “trifolia” — with 1-5″ long petioles. (Rarely, the leaves are five-foliate compound.) The leaflets are oval, hairy on the underside, with finely serrated margins, and rounded or wedge-shaped bottoms tapering to a short, fine tip. The leaflets are up to 2.5″ long and about 1″ wide. The terminal leaflet has a petiolule (stalk) up to 1″ long; the two lateral leaflets are nearly sessile. White, drooping, bell-shaped flowers in clusters of 5-12 arise from the axils of the leaves. Each flower is pendant on a long stalk, bell-shaped, about 8 mm long and about 6 mm wide. Flowers have five greenish-white sepals overlapping much of the petals, five bright white petals (visible through the gaps between the sepals) that flare at their tips, five stamens with white filaments and deep yellow-orange anthers, and a greenish-white style with a three-lobed stigma extending beyond the mouth of the bell. The flower stalks (pedicels) are about 1.5-2 times the length of the flower. The fruit is a greenish-white to brown, papery pod (like a “Chinese lantern”) that is about 3″ long and 2″ across with three lobes/chambers, pointed on their distal ends; each chamber contains up to four 1/4″ seeds. Both flowers and fruits are distinctive and easily recognizable.
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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)
