Biennials; short-lived; sexual; caudex not evident. Stems 1 per plant, arising from center of rosette near ground surface, (1.5-)3-11 dm, glabrous throughout. Basal leaves: blade obovate to oblanceolate, (4-)10-40 mm wide, margins serrate or dentate, ciliate-mucronate on teeth, trichomes often minute, surfaces glabrous or sparsely pubescent, trichomes simple, 0.1-0.6 mm. Cauline leaves: 7-15, often concealing stem proximally; blade auricles 3-12 (-17) mm, surfaces of distalmost leaves glabrous. Racemes 16-45-flowered, sometimes branched. Fruiting pedicels suberect to divaricate-ascending, straight to slightly curved, 5-23 mm, glabrous. Flowers ascending at anthesis; sepals glabrous; petals white, 3-5 × 1-1.5 mm, glabrous; pollen ellipsoid. Fruits divaricate-ascending, not appressed to rachis, rarely somewhat secund, curved, edges parallel, (4-)6-11.7 cm × 1-2 mm; valves glabrous; ovules 50-80 per ovary; style 0.1-0.7(-1) mm. Seeds uniseriate, 1.2-2.2 × 0.8-1.4 mm; wing continuous, 0.1-0.3 mm wide distally. 2n = 14. Flowering Mar-May. Rocky bluffs, cedar glades, wooded hillsides, floodplains; 100-500 m; Ont., Que.; Ala., Ark., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Ky., Md., Mass., Mich., Mo., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Vt., Va., W.Va., Wis. The taxon sometimes treated as Arabis laevigata var. missouriensis is here recognized as a separate species (Boechera missouriensis) based on its significantly longer petals (5-10 versus 3-5 mm) and distinctive, lyrate-pinnatifid basal leaves that persist well beyond anthesis.
Biennial herb to 1 m tall Stem: upright, unbranched or sparingly branched, with a waxy coating (glaucous). Flowers: in branched, drooping clusters, white or yellowish white, 3 - 6 mm long, barely exceeding sepals. Petals four. Stamens six. Fruit: a narrow pod, widely spreading, drooping or hanging downward, 5 - 10 cm long, 1.2 - 2 mm wide, on a 7 - 12 mm long stalk, flat, very curved. Seeds in one row, oblong, narrowly winged. Basal leaves: in a weak rosette, stalked, spatula-shaped, base tapering, tip rounded, sparsely toothed, sparsely hairy, with a waxy coating (glaucous). Stem leaves: alternate, stalkless, clasping stem, 5 - 15 cm long, narrowly lance-shaped, base lobed, sometimes toothed, with a waxy coating (glaucous). On average there are about thirteen leaves below the first cluster of flowers.
Similar species: The similar Boechera drummondii differs by having pods that are strongly upright at maturity. Boechera missouriensis differs in having petals that are half again as long as the sepals.
Flowering: late April to early August
Habitat and ecology: Fairly common in calcareous soils on shaded banks, usually in moist woods or more rocky areas.
Occurence in the Chicago region: native
Notes: Boechera laevigata gets the common name Smooth Bank Cress from growing on eroded banks.
Etymology: Boechera refers to the Danish botanist, Tyge Bocher. Laevigata means smooth.
Biennial to 1 m, simple or few-branched, glabrous and glaucous throughout, except the sparsely hirsutulous, spatulate basal lvs; cauline lvs (averaging ca 13 below the first fl) narrowly lanceolate, 5-15 cm, serrate to entire, usually sagittate at the sessile base; cal 3-5 mm; pet white, 3-6 mm, equaling to a fourth longer than the sep; pedicels at maturity widely spreading, 7-12 mm; frs widely spreading to somewhat decurved, arcuate, linear, flat, 5-10 cm נ1.2-2 mm, nerveless or faintly nerved to the middle; seeds in 1 row, oblong, narrowly winged; 2n=14. Woods and hillsides; Que. to S.D., s. to Ga. and Okla. Apr.-June. Var. burkii Porter, with nonsagittate cauline lvs, occurs from Pa. and Md. to Va. and W.Va., sometimes on shale-barrens.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Frequent but never common throughout the state. It prefers a rather sandy or gravelly soil and is restricted to the wooded slopes and high banks of streams. The leaves of this species are variable and one form has been named. I am including it under the species.