Arabis laevigata (Muhl.) Poir. - Smooth Rock Cress

Arabis laevigata plant

Family - Brassicaceae

Stems - To +50cm tall, erect, glabrous, glaucous, branching or simple, herbaceous, from a branched taproot, slightly angled from decurrent leaf midrib.

Arabis laevigata stemStem and clasping leaves.

Leaves - Alternate, sessile, clasping, auriculate. Basal rosette of serrate to crenate leaves. Leaves purplish, (especially below), often pubescent. Cauline leaves linear-lanceolate, +/-10cm long, +/-1cm broad, glabrous, glaucous, acute, entire to shallow serrate and often undulate near the base. Auricles rounded to subacute, completely surrounding the stem on larger leaves.

Arabis laevigata leaves

Inflorescence - Terminal and axillary racemes, loose in flower, elongating in fruit. Pedicels glabrous, to -5mm in flower, elongating in fruit to -2cm, erect to spreading.

Arabis laevigata inflorescence

Flowers - Petals 4, white, glabrous, tapering to the base, blunt to truncate or wavy at the apex, to +/-5mm long, slightly exceeding or equaling the sepals. Stamens 6, 4 alike and 2 slightly smaller. Filaments to 5mm long, white, glabrous, erect. Anthers yellow, 1.2mm long. Ovary cylindric, green, glabrous, 3.4mm long, .5mm in diameter, 2-valved. Style very short, .1-.2mm long. Stigma capitate. Sepals 4, light green, glabrous, 4-5mm long, 1-1.3mm broad, rounded at apex, slightly cupped, erect. Siliques long, arcuate, terete, thin, with a minute beak, glabrous, to +/-7cm long, 2mm in diameter.

Arabis laevigata calyxCalyx close-up.

Arabis laevigata flowerFlower close-up.

Flowering - April - June.

Habitat - Rocky woods and bluffs, low woods along streams.

Origin - Native to U.S.

Other info. - This indistinct plant is found mostly in the lower 1/2 of Missouri. The fruits of this species are long, thin, and curved and can help when trying to identify this species from others in the genus. Another species, A. missouriensis, is similar does not have glaucous stems.

Photographs taken at Eagle Bluffs Conservation Area, Boone County, MO., 4-11-04.


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