spotted Joe Pye weed

not listed

NNR - Unranked

SNR - Unranked

not listed

OBL - Obligate wetland

OBL - Obligate wetland

OBL - Obligate wetland

Spotted Joe Pye weed (var.maculatum) is a 24″ to 80″ tall, erect, perennial forb that rises from a fibrous roots and sometimes rhizomes.

The stems are erect and usually light green with purple spots but are sometimes more evenly purple. They are usually solid but are sometimes hollow near the base. They are usually not covered with a whitish, waxy coating (glaucous). They are hairless except for a covering of minute, short hairs near the top.

Most of the leaves are usually in whorls of 4 or 5, sometimes in whorls of 3 or 6. They do not have a tight bundle of small leaves in the leaf axils. They are on hairless, 1 ⁄16″ to 1″ long leaf stalks. The leaf blades are relatively thin, lance-shaped to elliptic or egg-shaped, 3″ to 10″ long, and 1″ to 3½″ wide. They are tapered to a sharp point at the tip and tapered gradually to the leaf stalk at the base. There is a single main vein. The upper surface is dull and hairless. The lower surface is paler green and usually hairless. The margins are toothed with sharp, forward-pointing teeth. The uppermost whorl of leaves, the whorl directly subtending the inflorescence, is not broader than the inflorescence. The leaf blades of this whorl are ⅝″ to 1″ long and 1 ⁄16″ to 3 ⁄16″ wide.

The inflorescence is a branched, elongated, flat-topped or nearly flat-topped array of numerous flower heads at the top of the stem.

Each flower head has 8 to 22, usually 10 to 16, pale purple to pink disk florets and no ray florets.

The fruit is a ⅛″ to 3 ⁄16″ long achene with a fluffy tuft of hairs attached.

24″ to 80″

Pale purple to pink

Holzinger’s eupatorium (Eupatorium purpureum var. holzingeri) stems are mostly green, purple only at the leaf nodes, and are rarely hollow near the base. The leaf undersurface is densely hairy. The inflorescence is dome-shaped, not flat-topped. The flower heads have 4 to 7 disk florets per head.

Bruner’s spotted Joe Pye weed (Eutrochium maculatum var. bruneri) stems are densely covered from the base to the inflorescence with minute, short hairs. The leaves are relatively thick. The leaf undersurface is densely hairy.

Spotted Joe Pye weed (Eutrochium maculatum var. foliosum) uppermost whorl of leaves is much larger, as broad or broader than the inflorescence. The leaf blades of this whorl are 3″ to 8″ long and ¾″ to 1½″ wide. It has been reported only in Cook County.

Sweet Joe Pye weed (Eupatorium purpureum var. purpureum) stems are mostly green, purple only at the leaf nodes, and are rarely hollow near the base. The inflorescence is dome-shaped, not flat-topped. The flower heads have 4 to 7 disk florets per head. The flowers are pale pink to purplish.

Wet to moist. Meadows, marshes, lakeshores. Full sun or partial shade.

July to September

Sources

3, 4, 7, 29, 30.

Native

Common

Joe Pye weeds were originally assigned to the genus Eupatorium. In 1836 a French botanist (Rafinesque) separated Joe Pye weeds from that genus and proposed assigning them to the genus Eutrochium. Unaware of Rafinesque’s work, in 1970 researchers at the Smithsonian Institution (King and Robinson) proposed the genus Eupatoriadelphus for Joe Pye weeds, and it was widely adopted. In 1987, further study by the same researchers convinced them to return Joe Pye weeds to Eupatorium. In 1999 and 2000, DNA studies at the University of Tennessee (Schilling) concluded yet again that Joe Pye weeds did not belong to Eupatorium, and they were returned to the genus Eupatoriadelphus. In 2004, a contributor to the Flora of North America (Lamont), recognizing the precedence of earlier-established names, transfered the species to Eutrochium.