This wildflower is a biennial or short-lived perennial that forms a low
rosette of basal leaves, from which one or more flowering stems develop
that are 4-14" long. The basal leaves are ¾-2" long and ¼-½" across;
they are oblanceolate to oblong-oblanceolate and pinnatifid (rarely
without lobes). The terminal lobes are larger in size than the lateral
lobes. The upper and lower surfaces of the basal leaves are grayish
green and either short-hairy or glabrous.
The stems are
erect, ascending, or sprawling; they
are usually short-hairy below and glabrous above, but sometimes
glabrous throughout. These stems are either branched above
or unbranched. The alternate leaves along each stem are ½-1½"
and up to ¼" across; they are linear-elliptic, linear-oblanceolate, or
linear-oblong in shape with smooth margins (rarely lobed or sparsely
dentate). The alternate leaves are grayish green, sessile, glabrous
along their upper surfaces, and either glabrous or short-hairy along
their lower surfaces. Each upper stem terminates in a raceme of
flowers. The flowers bloom near the apex of each raceme, while
seedpods develop below. Each flower spans ¼" across or a
more, consisting of 4 white petals, 4 green sepals, several stamens,
and a pistil with a short style. The sepals are lanceolate with blunt
tips and glabrous. The slender
pedicels are ¼-½" long and
blooming period occurs from late spring to mid-summer, lasting about 1
month. The flowers are replaced by narrowly cylindrical seedpods
(siliques) that are ¾-1¾" long, ascending, glabrous, and somewhat
flattened. Each seedpod contains a single row of seeds. The seeds are
about 1.0 mm. long, ovoid in shape, and somewhat flattened; they do not
possess winged margins of any significance. The root system consists of
a taproot. This wildflower reproduces by reseeding itself.
The preference is full or partial sun, mesic to dry conditions, and
soil that is sandy, gravelly, or rocky. Competition from taller ground
vegetation is not tolerated.
Sand Cress is occasional in northern Illinois, while in the rest of the
state it is absent. In addition to its range in North America, this
species is also found in Eurasia. Habitats consist of upland sand
prairies, upland gravel prairies, sand dunes near Lake Michigan, sandy
upland savannas, sandy upland woodlands, and rocky cliffs along rivers.
Occasional wildfires are probably beneficial in maintaining populations
of this species.
The nectar and pollen of
the flowers attract small bees, Syrphid flies, and small butterflies,
including the endangered Lycaeides
Other insects feed destructively on the foliage, flowers, and other
parts of Sand Cress and other Arabis
(Rock Cresses). These species
include the flea beetles Phyllotreta
, caterpillars of Plutella xylostella
(Diamondback Moth), and
caterpillars of the following Pierid butterflies: Anthocharis midea
(Falcate Orangetip), Euchloe
(Olympia Marble), Pieris napi
(Mustard White), and Pontia
(Checkered White). For North
America, little is known about the interrelationships of Sand
Cress with vertebrate animals.
A sandy savanna on a stabilized sand dune at the
Indiana Dunes State Park in NW Indiana.
Sand Cress is somewhat variable across its range
subspecies have been proposed that are differentiated by the shape of
the basal leaves and hairiness of the foliage. It is similar in
appearance to Arabidopsis
(Mouse-Ear Cress), Cardamine hirsuta
(Hairy Bitter Cress), and Cardamine
(Small-Flowered Bitter Cress). Sand Cress has slightly larger and
showier flowers (6-8 mm. across) than the preceding species. Other
characteristics that are useful for identification purposes include: 1)
whether or not the basal leaves are lobed, 2) whether or not the
cauline leaves along the stems are lobed, 3) whether the
siliques are erect, ascending, widely spreading, or drooping, and 4)
the length of the siliques. Some authors refer to Sand Cress as
to which genus it has been assigned recently.
Another common name of this species is Lyre-Leaved Rock Cress.