A delicate-looking plant with Mimosa-like leaves that quickly colonizes recently disturbed or burned areas. These were growing in Schenley Park, in a section of former lawn that is being allowed to grow into a meadow for better water retention. The cheery yellow flowers can keep coming for months; these were blooming in the middle of September.
Gray, like most older references, puts this species in the genus Cassia. Here is his description:
CASSIA [Tourn.] L. SENNA. Sepals 5, scarcely united at base. Petals 5, little unequal, spreading. Stamens 5-10, unequal, and some of them often imperfect, spreading; anthers opening by 2 pores or chinks at the apex. Pod many-seeded, often with croes partitions. — Herbs (in the United States), with simply and abruptly pinnate leaves, and mostly yellow flowers. (An ancient name of obscure derivation.)
Leaflets small, somewhat sensitive to the touch; stipules striate, persistent; a cup-shaped gland beneath the lowest pair of leaflets; anthers all perfect; flowers in small clusters above the axils; pods flat.
C. Chamaecrista L. (PARTRIDGE PEA.) Annual, suberect; branches usually simple, ascending; pubescence subappressed, usually scanty; leaflets 10-15 pairs, linear-oblong, oblique at the base; flowers (large) on slender pedicels, 2 or 3 of the showy yellow petals often with a purple spot at base; anthers 10, elongated, unequal (4 of them yellow, the others purple); style slender. — Sandy fields, Mass. to Minn., and southw., except in the upland regions. July-Sept.
A common tree in the forests around Pittsburgh, and also a favorite ornamental in urban and suburban yards. These trees were blooming in late April in open woods in Bird Park, Mount Lebanon.
Gray describes the genus and the species:
CÉRCIS L. REDBUD. JUDAS TREE. Calyx 6 toothed. Corolla imperfectly papilionaceous; standard smaller than tbe wings and inclosed by them in the bud; the keel petals larger and not united. Stamens 10, distinct, declined. Pod oblong, flat, many-seeded, the upper suture with a winged margin. Embryo straight.—Trees, with rounded heart-shaped simple leaves, caducous stipules, and red-purple flowers in umbel-like clusters along the branches of the last or preceding years, appearing before the leaves, acid to the taste. (The ancient name of the oriental Judas Tree.)
C. canadensis L (REDBUD.) Leaves pointed; pods nearly sessile above the calyx.—Rich soil, N. Y. and N. J. to Fla., w. to s. Ont., e. Neb., and Tex.—A small ornamental tree, often cultivated.
Crown Vetch is often planted to control erosion on hillsides; it also escapes freely and makes a nuisance of itself. But the bicolored flowers are pretty.
Gray describes the genus (he places it in Coronilla) and the species:
CORONILLA L. Calyx 5-toothed. Standard orbicular; keel incurved. Stamens diadelphous. 9 and 1. Pod terete or 4-angled, jointed; the joints eubrylindric. — Glabrous herbs or shrubs, with pinnate leaves, and the flowers in umbels terminating axillary peduncles. (Diminutive of corona, a crown, alluding to the inflorescence.)
C. vària L. A perennial herb with ascending stems; leaves sessile; leaf lets 15-25, oblong; flowers rose-color; pods coriaceous, 3-7 -jointed, the 4-angled joints 6-8 mm. long. — Roadsides and waste places, N. E. to N. J. (Nat. from Eu.)