Draba cuneifolia Nutt. ex Torr. & A. Gray

Whitlow Grass


CC = 5
CW = 5
MOC = 59

© DETenaglia

Family - Brassicaceae

Habit - Taprooted annual forb.

Stems - Ascending to erect, to 30 cm, 1 per plant but usually branched from near the base, hairy from the base to the tip of the inflorescence axis with simple and branched hairs.

Draba_cuneifolia_stem.jpg Stem with stellate pubescence.

© DETenaglia

Draba_cuneifolia_basal1.jpg Basal leaf disposition.

© SRTurner

Draba_cuneifolia_basal2.jpg Basal leaves, another angle.

The textured, speckled leaf appearance is characteristic.

© SRTurner

Leaves - In a basal rosette and also a few to several alternate, toward the bases of the stem branches, 0.5-5.0 cm long, sessile or nearly so, spatulate to oblanceolate, the margins noticeably few-toothed, especially above the middle, deep shiny green above, silvery green below, densely hairy on both surfaces with simple and branched hairs, the hair bases usually noticeably pustular.

Draba_cuneifolia_leaf1.jpg Leaf adaxial.

Dense covering of branched hairs.

© SRTurner

Draba_cuneifolia_leaf2.jpg Leaf abaxial.

© SRTurner

Draba_cuneifolia_leaves.jpg Leaves.

© DETenaglia

Inflorescences - Terminal unbranched racemes. Flowers almost always scattered along the inflorescences. Pedicels to 4 mm long in flower, longer in fruit, densely pubescent with simple and branched hairs.

Draba_cuneifolia_inflorescence.jpg Inflorescence.

© SRTurner

Flowers - Sepals 4, 1-2 mm long, pubescent externally with simple and branched hairs, glabrous internally. Petals 4, distinct, 2-5 mm long, white, rounded or more usually with a broad, shallow notch at the tip, glabrous. Claw to 1 mm long, slightly greenish. Limb to 4 mm long, 3 mm broad, emarginate at the apex, entire. Stamens 6, 4 larger and 2 smaller, distinct, erect. Ovary 2-locular, sessile. Styles absent or to 0.1 mm long.

Draba_cuneifolia_calyx.jpg Calyces and inflorescence axis.

© SRTurner

Draba_cuneifolia_corollas.jpg Flowers.

© SRTurner

Draba_cuneifolia_flower.jpg Corolla.

© DETenaglia

Fruits - Siliques 6-15 mm long, linear to narrowly oblong in outline, hairy. Seeds 20-80 per fruit.

Draba_cuneifolia_fruits.jpg Fruits.

© SRTurner

Flowering - February - May.

Habitat - Edges and tops of bluffs, rocky open glades and ledges, rocky open woods. Typically on calcareous substrates.

Origin - Native to the U.S.

Lookalikes - Other species of Draba; more broadly, small species of Cardamine and other springtime mustards.

Other info. - This springtime mustard is found throughout much of Missouri but is uncommon or absent in the Bootheel and large areas north of the Missouri River. Beyond Missouri its main range is in the southern half of the continental U.S., extending from Alabama to California and also into Mexico. It is easily recognized by its shining white flowers in the 4-petaled mustard pattern and its distinctive basal leaves bearing branched hairs. The petals are only slightly notched, if at all, and the leaves are confined to the near-basal portion of the stem. The plant can form cleistogamous flowers which self-pollinate without opening. These do not have petals.

Three varieties of this species are commonly recognized, with Missouri's plants all belonging to var. cuneifolia. The other two, var. integrifolia and var. sonorae, occur in California and Arizona and differ in fruit pubescence characteristics. The common name "whitlow grass" arose from an old belief that the plant would cure whitlow, an inflammation of horses' hooves.

Photographs taken at Danville Conservation Area, Montgomery County, MO., 3-19-04 (DETenaglia); also at Young Conservation Area, Jefferson County, MO, 4-17-2013; Matson Hill County Park, St. Charles County, MO, 4-14-2016; and Shaw Nature Reserve, Franklin County, MO, 4-13-2023 (SRTurner).