UPDATE: An earlier version of this article gave the wrong species name in the title.

Shorter than the more common Hollow Joe-Pye-Weed (E. fistulosum), with flatter cymes, and with leaves commonly in whorls of 4 rather than 6. The two species sometimes grow side by side, as they did here in a damp depression in Schenley Park, where they were both blooming in early August.

Most botanists today place the Joe-Pye-Weeds in the genus Eutrochium, making this Eutrochium maculatum; we keep the more familiar name for the convenience of Internet searchers.

Once again, we turn to Alphonso Wood for a description:

EUPATORIUM.

Dedicated to Eupator, king of Pontus, who first used the plant m medicine.

Flowers all tubular; involucre imbricate, oblong; style much exserted, deeply cleft; anthers included; receptacle naked, flat ; pappus simple, scabrous; achenia 5-angled.—Perennial herbs, with opposite or verticillate leaves. Heads corymbose. Flowers of the cyanic series, that is, white, blue, red, &c., never yellow.

* Leaves verticillate. Flowers purple.

E. Maculatum. (E. purpureum, ß. Darl.) Spotted Eupatorium.

Stem solid, striate, hispid or pubescent, greenish and purple, with numeróos glands and purple lines; the glands on the stem and leaves give out an acrid effluvium in flowering-time: leaves. triple-veined, 3-5 in a whorl.—Low grounds, U. S. and Can. Stem 4-6 ft. high. Leaves petiolate, 6-7 in. by 3-4 in., strongly serrate. Flowers purple. July-Sept.