Flowering Spurge (Euphorbia corollata)
A relative of the Christmas Poinsettia and Snow-on-the-Mountain, this plant easily fools us into thinking it has regular five-petaled flowers like a pink or a buttercup. Structurally, however, the apparent petals are actually bracts that surround a cluster of tiny flowers. Doubtless there is a moral lesson to be learned here, but we have not learned it yet. These plants grew in a sunny meadow in Sewickley Heights, where they were blooming in late August.
Flowers. Numerous; tiny and insignificant, but surrounded by five showy white regular bracts that look like petals; in irregular flattish umbels.
Leaves. Oblong-linear; blunt; entire; smooth; lower leaves more elliptical; alternate, but whorled at the base of the umbel of flowers.
Stem. Smooth; purplish; unbranched up to the whorl of leaves at the base of the umbel; about 3 feet (1 m) high.
The genus Euphorbia is enormous, so Gray helpfully divides it into sections. Here he describes the genus, the section, and the species:
EUPHÓRBIA L. SPURGE. Flowers monoecious, included in a cup-shaped 4-6-lobed involucre (flower of older authors) resembling a calyx or corolla, and usually bearing large thick glands (with or without petal-like margins) at its sinuses. Sterile flowers numerous and lining the base of the involucre, each from the axil of a little bract, and consisting merely ol a single stamen Jointed on a pedicel like the filament; anther-cells globular, separate. Fertile flower solitary in the middle of the involucre, soon protruded on a long pedicel, consisting of a 3-lobed and 3-celled ovary with no calyx (or a mere vestige). Styles 3, each 2-cleft; the stigmas therefore 6. Pod separating into three 1-seeded carpels, which split, plastically into 2 valves. Seed often caruncled (ours only in §§ 5 and 6). — Plants (ours essentially herbaceous) with a milky acrid juice. Peduncles terminal, often umbellate-clustered; in the first section mostly appearing lateral, but not really axillary. (Named for Euphorbus, physician to King Juba.)
§ 4. TITHYMALÓPSIS (Klotzsch &. Garcke) Boiss. Only the uppermost leaves whorled or opposite; erect perennials, with entire leaves equal at base; stipules none; involucres mostly 5-lobed, in the forks of the branches and terminal¡ inflorescence umbelliform.
E. corollàta L. (FLOWERING S.) Glabrous or sometimes sparingly hairy, 4-10 dm. high; root deep; stem usually simple for more than half its length; leaves ovate, lanceolate, or linear, entire, obtuse; umbel 5(3-7)-forked, and the forks again 2-3(or rarely 5)-forked; involucres long-peduncled, with showy white appendages (appearing like petals), the lobes minute and incurved; pod slender-pediceled, smooth; seeds thick, 2 mm. long or more, ash-colored, slightly uneven. — Rich or sandy soil, N. Y. to Fla., w. to Minn, and La.; also locally naturalized in N. E. July-Oct.