Northern Ontario Plant Database

Plant Description

Eutrochium maculatum (L.) E.E.Lamont

En: spotted Joe-Pye weed, purple Joe-Pye weed, purple boneset, spotted trumpetweed
Fr: eupatoire maculée, eupatoire pourpre

Asteraceae (Daisy Family)

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General: An erect perennial, 0.6—2 m tall; rhizomes are lacking. Stems are smooth (glabrous) to somewhat hairy, purple spotted to purple throughout, and solid above the base.

There are 3 varieties of spotted Joe-Pye-weed in Ontario. The variety typically found in Algoma is var. foliosum (Fernald) E.E.Lamont, which has upper leaf whorls wider than the flowering heads and stems that are primarily glabrous. The typical variety, var. maculatum with upper leaf whorls narrower than flowering heads and glabrous stems, is found in southwestern Ontario. The western var. bruneri (A.Gray) E.E.Lamont has densely hairy stems.

Leaves: Leaves are simple, petiolate, and whorled, usually with 4—5 leaves at each node. Petioles are 0.5—2 cm long; leaves are bright green and rough-textured (rugose) above, and prominently veined on the paler lower surface. Leaf blades are lanceolate, 8—25 cm long by 2—9 cm wide, pinnately-veined with a single midrib, and glabrous to slightly hairy. Leaf blades taper gradually to wedge-shaped (cuneate) bases and narrowly-pointed (acuminate) apices, margins are coarsely toothed (serrate).

Flowers: Plants in the Aster Family have flowers arranged in inflorescences called heads, each composed of few to many small flowers attached to a base covered with overlapping rows of bracts (phyllaries), forming an involucre. The heads of spotted Joe-Pye-weed are arranged in flat-topped corymb-like clusters. Each head has about 9—20 purplish disc flowers; ray flowers are lacking, and involucres are cylindrical, 6.5—9 mm long. Two slender pale style branches extend well beyond the anthers of the disc flowers. Plants with white flowers are rare (forma faxonii Fernald), but do occur. Flowers bloom in mid-summer.

Fruit: Narrow, 5-angled achenes, 3—5 mm long, ellipsoid, single-seeded, and topped by 25—40 pale brown bristles that aid in wind dispersal.

Habitat & Range: Moist to damp rich soils (often calcareous) along pond and stream margins, in wet meadows, at the edges of marshes, swamps, and moist to wet portions of rights-of-way. Spotted Joe-Pye-weed is found throughout the Algoma District and most of Ontario. The species complex, Eutrochium maculatum, is native across much of temperate and southern boreal North America, but is absent from the extreme south, southwest, and north. Of the three varieties, var. foliosum has the most northerly range, extending from Nova Scotia to northern Ontario and south into New England, var. maculatum has a more southeastern range, extending from Newfoundland to Ontario and south through the eastern U.S., while the western var. brunei extends west from Ontario to British Colulmbia and south through west-central U.S.

Similar Species: Purple Joe-Pye-weed (Eutrochium purpureum (L.) E.E.Lamont) is most similar to spotted Joe-Pye-weed, but occurs only in southern Ontario. Flowers of purple Joe-Pye-weed occur in open convex to rounded clusters, with heads of 4—7 disc flowers. Their stems are green to purple, but not purple-spotted, although nodes may be purple; leaves usually occur in whorls of 3—4.

A related plant, common boneset (Eupatorium perfoliatum) has white-flowering heads that have 7-11 disc flowers in each head; it can be differentiated from white-flowered plants of spotted Joe-Pye-weed by the pairs of connate-perfoliate leaves subtending the flowers.