Boechera dentata (Raf.) Al-Shehbaz & Zarucchi

Rock Cress

© SRTurner

Family - Brassicaceae

Habit - Biennial forb from a thin taproot or fibrous roots.

Stems - Spreading to weakly ascending, to 50 cm, multiple from base, occasionally branching in upper half, pubescent with 2-4 branched hairs.

	Stem and leaves.
© SRTurner

	Stem and leaf (adaxial).
© SRTurner

Leaves - Alternate, simple, often ascending on stem. Leaves pubescent with simple hairs on the upper surface and with mostly 3- or 4-branched hairs on the undersurface. Basal leaves to 15 cm long, obovate to oblanceolate in outline, irregularly toothed, narrowed at the base to a short or long petiole. Stem leaves 1-6 cm long, narrowly oblanceolate to nearly linear in outline, sessile, clasping the stem, with pointed auricles, sharply and irregularly toothed, nearly glabrous on upper surface, with with minutely hairy margins.

	Leaf abaxial.
© SRTurner

	Leaf abaxial.
© SRTurner

	Basal and stem leaves.
© DETenaglia

Inflorescence - Terminal and axillary racemes, compact in flower, much elongated in fruit, to 20 cm. Pedicels to 2 mm long in flower, pubescent with simple and branching hairs.

	Inflorescence.
© SRTurner

Flowers - Sepals 4, free, 1.5-2.5 mm long, narrowly oblong, green, sparsely pubescent. Petals 4, free, 2-3 mm long, white, glabrous. Stamens 6. Filaments to 2 mm long. Anthers yellow. Ovary longer than broad, terete, stellate-pubescent.

	Flowers.
© SRTurner

Fruits - Siliques strongly flattened, to 4 cm long, glabrous or stellate-pubescent, spreading, or ascending with maturity. Seeds in 1 row in each locule, 1.0-1.2 mm long, elliptic to narrowly oblong in outline, not flattened or winged, the surface roughened, orange.

	Fruits.
© SRTurner

Flowering - April - June.

Habitat - Bottomland and mesic forests, streambanks, bases of bluffs.

Origin - Native to the U.S.

Lookalikes - Boechera canadensis and other members of the genus.

Other info. - This very inconspicuous plant is found scattered throughout most of Missouri. Its U.S. range is mostly within the Midwest, along with small parts of the Northeast and Canada. It favors rich, moist, and relatively undisturbed areas. The flowers are tiny and easily missed. Identification is not difficult when the plant is flowering. Look for the inconspicuous inflorescences and weak stems with clasping leaves.

This species has long been called Boechera shortii. Steyermark named two varieties for Missouri plants. Variety shortii has pubescent ovaries and fruit, whereas in var. phalacrocarpa (M. Hopkins) Steyerm. these structures are glabrous. Both are fairly common in the state. However, since the degree of pubescence is continuously variable and does not correlate with any other characters, these varieties are not currently formally recognized in Missouri. The species was also formerly placed in the genus Arabis. Yet another name is Borodinia dentata (Raf.) P.J. Alexander & Windham.

Photographs taken at Leawood City Park, Leawood, Kansas, 4-27-00, and in the Hercules Glade Wilderness, Mark Twain National Forest, Taney County, MO., 4-8-01 (DETenaglia); also at Young Conservation Area, 4-18-2015, Little Lost Creek Conservation Area, Warren County, MO, 3-30-2012, and Meramec Conservation Area, Franklin County, MO, 4-18-2020 (SRTurner).