Description: This native plant is a biennial that consists of a rosette of basal leaves during the first year. The basal leaves are up to 6" long and 2" across; they are oblanceolate or obovate, dentate along the margins, and hairy underneath. Each basal leaf tapers to a petiole-like base that is long and slender, while its tip is acute to blunt. During the second year, one or more stems with alternate cauline leaves develop from the center of the rosette, which withers away. Upon reaching maturity, Toothed Rock Cress is 1½–3' tall. The erect to ascending stems are light green, finely pubescent, terete, and sparingly branched. The cauline leaves are up to 4" long and 1½" across; they are oblanceolate to obovate and dentate along their margins. The upper surface of each cauline leaf is sparingly covered with fine hairs or hairless, while the lower surface is conspicuously hairy. Each cauline leaf clasps the stem with a pair of basal lobes (it is auriculate).
The upper stems terminate in floral
racemes up to 1' long. Each flower is about 1/8" across, consisting of 4
sepals, 4 petals, an ovary with a stout style, and several stamens with pale
yellow anthers. The petals are white and oblanceolate; they barely extend
beyond the sepals. The sepals are lanceolate-oblong, light green to reddish
green, and finely hairy. The pedicel of each flower is short, stout, and
conspicuously hairy. The blooming period occurs during the late spring or early
summer and lasts about a month. Each flower is replaced by a slender
cylindrical silique about ¾–1½" long that contains a single
row of seeds. The siliques are ascending to spreading along the central stalk
of the raceme; they are more or less straight and don't droop. The outer
surface of each silique is light green to reddish purple and glabrous or finely
pubescent (usually the latter). The seeds are quite small (about 1 mm. long),
oblongoid, and somewhat flattened; they lack winged margins. The root system
consists of a taproot. This plant spreads by reseeding itself.
Cultivation: This plant is typically found in
dappled sunlight to medium shade, moist conditions, and fertile loamy
soil.
Range & Habitat:
Toothed Rock Cress occurs occasionally in northern and central Illinois, while
in the southern section of the state it is uncommon or absent. Habitats include
moist to mesic deciduous woodlands, wooded floodplain areas along rivers, banks
of small streams, rocky bluffs, and shaded limestone cliffs.
Faunal Associations: The small flowers attract
various bees, Syrphid flies, Dance flies (Empis spp.), and miscellaneous
other insects. The bee visitors include Cuckoo bees (Nomada spp.),
Halictid bees, Andrenid bees, and Little Carpenter bees. The bees suck nectar
or collect pollen, while the flies suck nectar or feed on pollen. Information
about other floral-faunal relationships is currently
unavailable.
Photographic Location:
A low wooded area along a river in Vermillion County, Illinois.
Comments: This is one of the woodland Arabis
spp. (Rock Cresses). As a group, they are usually tall-growing, but not
very showy because of their small flowers. It can be somewhat tricky to
distinguish these species and several physical characteristics should be
considered. Toothed Rock Cress has: 1) stems with pubescent hairs throughout,
2) terete siliques that are spreading to ascending (but not drooping nor
stiffly erect), 3) auriculate leaves with basal lobes that clasp each stem
throughout its length, and 4) very small flowers (about 1/8" across). Other
Rock Cresses often have: 1) hairless stems or stems that are hairy only toward
the bottom, 2) siliques that are flattened, droop downward, or are held stiffly
erect, 3) cauline leaves that are sessile, or have basal lobes that clasp each
stem only toward the bottom, and 4) flowers that are about 1/4" across. Another
scientific name of Toothed Rock Cress is Arabis
dentata.