Tall Thoroughwort (Eupatorium altissimum)

Eupatorium altissimum

Long stands of this dusty white thoroughwort line our highways. The narrow grey-green three-ribbed leaves (sometimes there are five ribs) are distinctive, and the mounds of white flowers are very attractive to honeybees. “All specimens in the Herbarium were collected recently,” says the 1951 Check List of the Vascular Flora of Allegheny County. “This is a Mississippi Valley species, entering the State from the southwest, particularly along the river bluffs.” Since then, the plant has become very much at home here, but it is still found mostly along the highways and railroads by which it entered.

This is a very common species here, but oddly underrepresented in photographs. As usual, Father Pitt donated these pictures to Wikimedia Commons, and these half-dozen photographs exactly doubled the collection for this species.

Gray describes the genus and the species:

EUPATORIUM [Tourn.] L. THOROUGHWORT. Heads discoid, 3-many-flowered; flowers perfect. Involucre cylindrical or bell-shaped, of more than 4 bracts. Receptacle flat or conical, naked. Corolla 5-toothed. Achenes 5-angled; pappus a single row of slender capillary barely roughish bristles. Erect perennial herbs, often sprinkled with bitter resinous dots, with generally corymbose heads of white, bluish, or purple blossoms, appearing near the close of summer. (Dedicated to Eupator Mithridates, who is said to have used a species of the genus in medicine.)

Heads 3-20-flowered; involucre of 8-15 more or less imbricated and unequal bracts, the outer ones shorter; flowers white or nearly so.

Leaves sessile or nearly so, with a narrow base, mostly opposite; heads mostly 5-flowered.

Bracts not scarious or only obscurely so, obtuse, at length shorter than the flowers.

E. altissimum L. Stem stout and tall, 1-2 m. high, downy leaves lanceolate, tapering at both ends, conspicuously 3-nerved, entire, or toothed above the middle, 0.5-1.3 dm. long, the uppermost alternate; corymbs dense; bracts of the involucre obtuse, shorter than the flowers. Dry soil, Pa. to Minn., Neb., and southw.

Zigzag Goldenrod (Solidago flexicaulis)

Photographed September 10.

A distinctive goldenrod that likes clearings in the woods or the banks of a stream. Its broad rounded toothy leaves are distinctive, and it takes its common name from the angled stems, which zigzag from one leaf to the next. (“Zigzag” is a technical term in botany.) The flowers grow in a wand at the top of the stem, with more flowers filling in the leaf axils.

Gray gives us a description of the genus Solidago:

SOLIDAGO L. GOLDEN-ROD. Heads few-many-flowered, radiate; the rays 1-16, pistillate. Bracts of the involucre appressed, destitute of herbaceous tips (except nos. 1 and 2). Receptacle small, not chaffy. Achenes many-ribbed, nearly terete; pappus simple, of equal capillary bristles. —Perennial herbs, with mostly wand-like stems and sessile or nearly sessile never heart-shaped stem-leaves. Heads small, racemed or clustered; flowers both of the disk and ray yellow (cream-color in no. 6). Closely related species tending to hybridize freely. (Name from solidare, to join, or make whole, in allusion to reputed vulnerary qualities.)

Gray makes this species part of Solidago latifolia, so we turn to Britton for a description of the species according to current taxonomy (note his use of the technical botanical term we mentioned above):

Solidago flexicaulis L. ZIG-ZAG OR BROAD-LEAVED GOLDENROD. Stem glabrous, angled, usually simple, zig-zag, 3-9 dm. high. Leaves thin, ovate, acuminate at the apex, somewhat pubescent, or glabrous beneath, sharply serrate, 5-17 cm. long, 2-10 cm. wide, the uppermost sometimes lanceolate and entire or nearly so; heads about 6 mm. high; bracts of the involucre obtuse to acutish; achenes hirsute-pubescent. In rich woods, N. B. to Ga., west to S. Dak. and Kans. July-Sept.

Evening Primrose (Oenothera biennis)

Photographed September 10.

In cool weather it is sometimes possible to catch an Evening Primrose open in the middle of the day, though the flowers usually close by the middle of the morning. In an earlier article, we gave this description of it:

A tall and stately weed whose flowers we almost never get to see in their full glory. It’s a night-bloomer, opening at dusk and fading in the early hours of the morning.

Flowers. Pale yellow; four broad petals; cross-shaped anther in the middle; borne in branching racemes.

Leaves. Lanceolate, sessile, slightly toothed; net-veined, with center rib often reddish toward base; alternate; thick on the stem, with branches or abortive branches in axils; mostly smooth.

Stem. Stout; somewhat sticky; woody below, with dark brownish stripes; to 6 feet or more; much branched.