Our broad modern highways seem to have been the making of this plant around here. It likes the median strips of interstate highways better than any other environment, and its grey-green leaves topped with dusty white flowers make it a decorative companion to the goldenrods that often grow in the same places. The plant above was growing along the side of a highway near Rostraver; the one below in a vacant lot in West Mifflin; both were blooming in late September.

Flower heads. Rayless, white, borne in layers of flat-topped clusters.

Leaves. Dark greyish-green; lanceolate; the upper ones entire, the lower toothed past the midpoint; with three prominent parallel veins. Often there are two smaller leaves where the petiole meets the stem.

Stems. Straight and study; greyish-green, paler than the leaves, often with a brown cast toward the base; much branched.

This plant apparently hybridizes with E. serotinum, and is easily confused with it, probably even on this site.

Gray describes the genus and the species:

These beautiful flowers, close relatives of the garden Bachelor’s Button (Centaurea cyanus), seem to be found almost exclusively along railroads. We have three pictures now of this species, each beside a different railroad; this particular plant was part of a colony growing by the railroad viaduct that separates the South Side Flats from the Slopes, where it was blooming at the end of July. (The other two pictures are here and here.)  The color is variable from purple through white, but this purplish pink is by far the most common color.

Gray describes the genus and the species:

CENTAUREA L. STAR THISTLE. Heads many-flowered; flowers all tubular, the marginal often much larger (as it were radiate) and sterile. Receptacle bristly. Involucre ovoid or globose, imbricated; the bracts margined or appendaged. Achenes obovoid or oblong, compressed or 4-angled, attached obliquely at or near the base; pappus setose or partly chaffy, or none. Herbs with alternate leaves; the single heads rarely yellow. (Kentaurie, an ancient Greek plant-name, poetically associated with Chiron, the Centaur, but without wholly satisfactory explanation.)

C. maculosa Lam. Pubescent or glabrate, with ascending rather wiry branches; involucre ovoid-cainpanulate, in fruit becoming open-campanulate; the outer and middle ovate bracts with rather firm points and with 5-7 pairs of cilia at the dark tip; innermost bracts elongate, entire or lacerate; corollas whitish, rose-pink, or purplish, the marginal falsely radiate. Waste places, roadsides, etc., N. E. to N. J. (Adv. from Eu.)

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.

Probably the most common species of Joe-Pye-Weed in our area. Most botanists today put Joe-Pye-Weeds in the genus Eutrochium; we keep the name Eupatorium for the convenience of Internet searchers.

This magnificent plant, with its domes of dusty-rose flowers on towering stems, is common in damp fields and roadsides everywhere; these plants grew in a moist depression in Schenley Park, side by side with their close cousins the Spotted Joe-Pye-Weeds (E. maculatum). Enlightened gardeners who have space for a few eight-foot towers in their perennial beds are beginning to discover and make use of this plant, which can now be seen in some of Pittsburgh’s most tasteful gardens.

The taxonomy of the Joe-Pye-Weeds seems to be in an awful mess. Alphonso Wood’s Class-Book of Botany seems to be closest to the modern botanists’ classification of this species, so we use Wood’s description here:

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. fistulosum Barratt. (E. purpureum Willd. in part. E. incarnatum Linn., in part. E. purpureum, v. angustifolium T. & G.) Trumpet-weed.—Stem fistulous, glabrous, glaucous-purple, striate or fluted; leaves in about 12 whorls of 6s, largest in the middle of the stem, rather finely glandular-serrate; midvein and veinlets livid purple; corymb globose, with whorled peduncles.—Thickets, U. S. and Can., very abundant in the Western States! Height 6-10 ft., hollow its whole length. Leaves, including the 1″ petiole, 8″ by 2″. Corymb often 1 ft. diam. Flowers purple. The glaucous hue and suffused redness of this majestic plant are most conspicuous in flowering-time. It does not appear to possess the acrid properties of E. maculatum. July—Sept.

Also called “Daisy Fleabane,” “Fleabane Daisy,” “Plains Fleabane,” “Prairie Fleabane,” and probably many other names. Pittsburghers usually call them “little daisies.” Old herbal legend has it that dried plants repel fleas. Fleabane is very common around here; if it were not, it would be treasured as a garden ornamental. It blooms for a good bit of the summer; these were blooming in late June in a clearing in the woods in Scott Township.

The seventh edition of Gray lists this as Erigeron ramosus, though the sixth had listed it as E. strigosus.

ERIGERON L. FLEABANE. Heads many-flowered, radiate, mostly flat or hemispherical; the narrow rays very numerous, pistillate. Involucral bracts narrow, equal, and little imbricated, never coriaceous, neither foliaceous nor green-tipped. Receptacle flat or convex, naked. Achenes flattened, usually pubescent and 2-nerved; pappus a single row of capillary bristles, with minuter ones intermixed, or with a distinct short outer pappus of little bristles or chaffy scales. Herbs, with entire or toothed and generally sessile leaves, and solitary or corymbed naked-pedunculate heads. Disk yellow; rays white, pink, or purple. (The ancient name presumably of a Senecio, from er, spring, and geron, an old man, suggested by the hoariness of some vernal species.)

E. ramosus (Walt.) BSP. (DAISY F.) Stem panicled-corymbose at the summit, roughish like the leaves with minute appressed hairs, or almost smooth; leaves entire or nearly so, the upper lanceolate, scattered, the lowest oblong or spatulate, tapering into a slender petiole; rays white, twice the length of the minutely hairy involucre. (E. strigosus Muhl.) Fields, etc., common. June-Oct. Stem smaller and more simple than the preceding [E. annuus], with smaller heads but longer rays. Var. DISCOIDEUS (Robbins) BSP., with the rays minute, scarcely exceeding the involucre, occurs in s. N. E. and N. Y.