Zizia aurea
golden alexanders [Blooms: Apr/May–?]
Golden alexanders (Zizia aurea) flowers and fruit. Bottom right: golden alexanders flowers. The stamens (with their terminal anthers) protrude through the spaces between the still-furled petals. Top right: golden alexanders flowers with a margined calligrapher flower fly (Toxomerus marginatus) for scale. The two styles each flower possesses (arrows) can be seen when the flower is in profile; the stamens have not yet been deployed. Top left: the underside of a golden alexanders compound umbel of flowers. Bottom left: seed capsules of golden alexanders. Note that many of these fruits have the remnants of the two styles at their apex.
The tips of the upper stems of golden alexanders produce flat to slightly rounded compound umbels 2-3″ across with about a dozen umbellets of tiny, golden-yellow flowers. Each umbellet has about 20 flowers; the central flower is sessile (or nearly sessile) while all the other blooms in the umbellet are on short stalks (pedicels), a character of the genus. Each 1/8″ wide flower consists of an insignificant calyx, five yellow petals that are persistently incurled, five stamens with yellow anthers projecting through the spaces between the petals, and two styles. The fruits are a ribbed (not winged) 2 mm long capsule with a flat top from which the remnants of the two styles project. Golden alexanders prefers full to partial sun and is tolerant of a range of habitat quality. The yellow-flowered variety of meadow parsnip (Thaspium trifoliatum var. aureum) is very similar to golden alexanders but has basal leaves that are simple rather than trifoliate compound, but I have not seen meadow parsnip in Jackson Park. John Hilty warns that “Golden Alexanders should not be confused with Pastinaca sativa (Wild Parsnip), which is a weedy Eurasian biennial. The latter is taller, blooms later, and has more leaflets in each compound leaf.” Wild parsnip DOES occur in Jackson Park, but it is relatively rare, twice the size of golden alexanders, has robust, strongly ribbed stems, and a large, flattened, winged fruit. Heartleaf alexanders (Zizia aptera) is also very similar, but only the uppermost leaves are compound; all the lower and middle leaves are simple and heart-shaped.
Golden alexanders (Zizia aurea) stems and leaves. Bottom right: a stem of golden alexanders with a single compound leaf attached to the far side of the stem. The basal sheath of the leaf petiole is indicated with an arrow; each of the 14 leaflets in this leaf is marked with a white dot at the tip of the leaflet. Top: a single compound leaf of golden alexanders showing the upper surface of the leaf (left image) and the underside of the same leaf (right image). The sheath on the end of the petiole is indicated by a white arrow. Bottom left: a closer view of the six leaflets at the tip of the leaf figured above.
Golden alexanders is a native perennial that stands up to 2.5 feet tall; it is one of the commonest wildflowers in Jackson Park. The stems are light green, shiny, and hairless. The leaves are all odd-pinnate compound with 3-5 leaflets; lower leaves have long petioles, but the petioles decrease in size the higher the leaf is on the plant. The leaflets are up to 3″ long and about two-thirds as wide, with serrated margins. The leaflet shape is highly variable — they may be lance-shaped, broadly oblong, oval, or heart shaped; the larger leaflets may have one or two additional cleft lobes.
A stand of golden alexanders (Zizia aurea) just north of West Lagoon. The insert shows a close-up of golden alexanders flowers with a flower fly (a margined calligrapher) for scale.
Golden alexanders is a native perennial that stands up to 2.5 feet tall; it is one of the commonest wildflowers in Jackson Park. The stems are light green, shiny, and hairless. The leaves are all odd-pinnate compound with 3-5 leaflets; lower leaves have long petioles, but the petioles decrease in size the higher the leaf is on the plant. The leaflets are up to 3″ long and about two-thirds as wide, with serrated margins. The leaflet shape is highly variable — they may be lance-shaped, broadly oblong, oval, or heart shaped; the larger leaflets may have one or two additional cleft lobes. The tips of the upper stems produce flat to slightly rounded compound umbels 2-3″ across with about a dozen umbellets of tiny, golden-yellow flowers. Each umbellet has about 20 flowers; the central flower is sessile (or nearly sessile) while all the other blooms in the umbellet are on short stalks (pedicels), a character of the genus. Each 1/8″ wide flower consists of an insignificant calyx, five yellow petals that are persistently incurled, five stamens with yellow anthers projecting through the spaces between the petals, and two styles. The fruits are a ribbed (not winged) 2 mm long capsule with a flat top from which the remnants of the two styles project. Golden alexanders prefers full to partial sun and is tolerant of a range of habitat quality. The yellow-flowered variety of meadow parsnip (Thaspium trifoliatum var. aureum) is very similar to golden alexanders but has basal leaves that are simple rather than trifoliate compound, but I have not seen meadow parsnip in Jackson Park. John Hilty warns that “Golden Alexanders should not be confused with Pastinaca sativa (Wild Parsnip), which is a weedy Eurasian biennial. The latter is taller, blooms later, and has more leaflets in each compound leaf.” Wild parsnip DOES occur in Jackson Park, but it is relatively rare, twice the size of golden alexanders, has robust, strongly ribbed stems, and a large, flattened, winged fruit. Heartleaf alexanders (Zizia aptera) is also very similar, but only the uppermost leaves are compound; all the lower and middle leaves are simple and heart-shaped.
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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)
