59. Boechera missouriensis (Greene) Al-Shehbaz, Novon. 13: 387. 2003.
Arabis missouriensis Greene, Repert. Spec. Nov. Regni Veg. 5: 244. 1908; A. laevigata (Muhlenberg ex Willdenow) Poiret var. heterophylla (Nuttall) Farwell; A. laevigata var. missouriensis (Greene) H. E. Ahles; A. missouriensis var. deamii (M. Hopkins) M. Hopkins; A. viridis Harger; A. viridis var. deamii M. Hopkins
Biennials; short-lived; sexual; caudex not evident. Stems usually 1 per plant, arising from center of rosette near ground surface, 2-7.5 dm, sparsely pubescent proximally, trichomes simple, to 0.5 mm, or glabrous throughout. Basal leaves: blade oblanceolate, 5-18 mm wide, margins lyrate-pinnatifid, often ciliate-mucronate on lobes, trichomes minute, surfaces glabrous or sparsely pubescent, trichomes simple, 0.1-0.5 mm. Cauline leaves: 10-45, often concealing stem proximally; blade auricles 1-5 mm, surfaces glabrous. Racemes 18-47 -flowered, sometimes branched. Fruiting pedicels suberect to divaricate-ascending, straight or slightly curved, 5-13 mm, glabrous. Flowers ascending at anthesis; sepals glabrous; petals white, 5-10 × 1-1.5 mm, glabrous; pollen ellipsoid. Fruits ascending to divaricate-ascending, not appressed to rachis, not secund, curved, edges parallel, 6-11 cm × 1.5-2 mm; valves glabrous; ovules 60-86 per ovary; style 0.1-1 mm. Seeds uniseriate, 1.2-2 × 1-1.2 mm; wing continuous, 0.1-0.4 mm wide.
Flowering Mar-Jun. Rocky bluffs, wooded slopes, valley bottoms; 50-300 m; Ark., Conn., Ga., Ill., Ky., Mass., Mich., Minn., Mo., N.Y., N.C., Okla., S.C., Wis.
Boechera missouriensis occasionally has been treated as a variety of B. laevigata. With its significantly longer petals (5-10 versus 3-5 mm) and distinctive, lyrate-pinnatifid basal leaves that persist well beyond anthesis, it warrants recognition as a species.