Northern Ontario Plant Database

Plant Description

Apocynum androsaemifolium L.

En: spreading dogbane, creeping dogbane, bitter dogbane, flytrap dogbane, low dogbane, dwarf dogbane
Fr: apocyn à feuilles d'androsème, herbe à la puce, apocyn nain
Oj: makonagizh-ojiibik, midewijiibik, mi/agoosing ezhianaagwak, makonagizhiijiibik

Apocynaceae (Dogbane Family)

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General: An erect, branching perennial, to 1 m tall, spreading by underground rhizomes to form dense colonies. Above ground stems are smooth (glabrous) and often dark reddish-purple; leaves often appear to be drooping. The description below refers to subsp. androsaemifolium, which occurs across most of Canada; subsp. pumilum (A.Gray) B.Boivin is found only in British Columbia. Warning: All parts of the plant have a milky sap that contains toxic glycosides; therefore, spreading dogbane should not be ingested or fed to animals. A rash may develop on some people if bare skin is exposed to sap from broken stems or leaves of this plant.

Leaves: Opposite, simple, pinnately-veined, and short-petiolate. Leaves are lanceolate, elliptic, or ovate, 6—10 cm long by 2—5 cm wide, with broadly-tapering to rounded bases, pointed (acute to acuminate) apices, and entire margins. The midrib of the leaf is often reddish and extends slightly beyond the leaf blade, forming a slender, mucronate tip at the leaf apex. Leaves are dark green and smooth above, paler and finely hairy beneath; in autumn, leaves turn yellow.

Flowers: Bisexual, fragrant, with several, nodding flowers borne in open, branched, terminal and axillary inflorescences (cymes). Flowers have a small, 5-lobed, green calyx and a 5-lobed, bell-shaped (campanulate), pink-tinged or white corolla, striped with dark pink inside, to 5—7 mm long. The tips of the corolla lobes curve back. Dogbane flowers each have 2 distinct ovaries that are united at the tip by a common, 2-lobed stigma; the 5 stamens have broad, triangular anthers that surround the stigma. Flowers bloom in summer.

Fruit: Long, slender dry fruit (follicles), 7—20 cm long, borne in pendant pairs. Similar to milkweed 'pods', each creeping dogbane follicle opens along one suture line to release the 2.5—3 mm long seeds, each ending in a small tuft of silky hairs, 1—2 cm long. Fruits mature in late summer (August).

Habitat and Range: Dry forest borders, open woodlands, rocky slopes, open fields, and roadsides. Spreading dogbane is native throughout most of North America. In Canada, it extends from insular Newfoundland west to the Yukon; it has not been found in Labrador or Nunavut. Its range in Ontario extends north to Sandy Lake (ca. 53°N) (Scoggan 1978).

Similar Species: The leaves of ovalleaf bilberry (Vaccinium ovalifolium Sm.) are similar in shape to those of spreading dogbane, but bilberry leaves are arranged alternately on the stem. Canada fly honeysuckle (Lonicera canadensis Bartram ex Marshall) also has opposite, ovate leaves, but has yellow flowers and a fleshy fruit, with two red berries fused at the base. Leaves of both species lack the mucronate tip typical of spreading dogbane.