Mustard family (Brassicaceae)
Description: This perennial wildflower is ½–1½' tall with an erect stem that is unbranched or sparingly branched toward the apex where the inflorescence occurs. The central stem is medium green, glabrous, and terete; it occasionally has fine longitudinal ridges. There are both basal leaves and alternate leaves. The blades of the basal leaves are up to 1¼" long and 1" across; they are oval to orbicular in shape, medium green, glabrous, and smooth or undulate along their margins. The slender petioles of the basal leaves are usually longer than the blades. The alternate leaves are produced sparingly along the central stem; they are up to 2" long and 1" across, medium green, and glabrous. The alternate leaves are oblong-ovate in shape and their margins are smooth, undulate, or bluntly dentate; at the base, each alternate leaf is sessile or short-petioled. The central stem terminates in a raceme of flowers; the flowers usually bloom in the upper half of the raceme, while their siliques (narrowly cylindrical seedpods) develop below. Each flower consists of 4 petals, 4 sepals, 6 stamens, and a pistil with a single style; when the flower is fully open, it spans about ½" across. The petals are white with rounded tips. The glabrous sepals are initially green, but they become yellow as they age. The petals are much longer than the sepals. Each flower has a slender pedicel about ½" long. The blooming period occurs from mid- to late spring and lasts about 3 weeks. The flowers are sometimes fragrant. Each flower is replaced by a slender hairless silique about 1" long that is somewhat flattened. The siliques are ascending to erect; they eventually divide into two parts to release their seeds. These seeds are ovoid, somewhat flattened, and wingless; they are arranged in a single row in each silique. Each plant has a swollen tuberous rootstock at the base of the central stem; this tuberous rootstock has spreading fibrous roots that occasionally produce small tubers. New plants are created from either the seeds or tubers.
Cultivation: The preference is partial sun or dappled sunlight, wet to moist conditions, and a loose fertile loam with organic material. Shallow standing water is tolerated if it is temporary; full sun is tolerated if the ground is consistently moist. Most growth and development occurs during the spring before the canopy trees leaf out.
Range & Habitat: The native Spring Cress is occasional to locally common in most areas of Illinois; it is less common or absent in the SW section of the state (see Distribution Map). This species may be less common than in the past. Habitats include low woodlands along rivers, edges of vernal pools in woodlands, damp depressions in rocky bluffs, woodland seeps and springs, and damp meadows.
Faunal Associations: The nectar of the flowers attracts cuckoo bees (Nomada spp.), mason bees (Osmia spp.), little carpenter bees (Ceratina spp.), Halictid bees (Augochlorella spp., Halictus spp., & Lasioglossum spp.), Andrenid bees (Andrena spp.), bee flies (Bombylius spp.), dance flies (Empis spp.), Syrphid flies (miscellaneous), small- to medium-sized butterflies (miscellaneous), and skippers (miscellaneous). Some of the bees also collect pollen. The flea beetles Phyllotreta oblonga and Phyllotreta bipustulata feed on Spring Cress and other Cardamine spp. (Bitter Cress species). Mammalian herbivores usually avoid the consumption of Spring Cress because its foliage is pungent and somewhat bitter.
Photographic Location: A low woodland along the Sangamon river in Piatt County, Illinois.
Comments: Spring Cress is one of the more attractive members of the Mustard family as its flowers are fairly large (spanning about ½" across). This wildflower favors the more damp areas of woodlands and it is sometimes found in soggy meadows. Another native species, Cardamine douglassii (Purple Cress), is very similar to Spring Cress. Both species prefer similar habitats, bloom during the spring, and their flowers and foliage are similar to each other. Purple Cress differs from Spring Cress by the purplish-pink tint of its flower petals, sepals that are dark purple and hairy, and stems that are hairy toward the base. It has a tendency to bloom about 2 weeks before Spring Cress. Other Cardamine spp. (Bitter Cress species) in Illinois have either smaller flowers (about ¼" across or less) or at least some of their leaves are deeply divided into lobes (either pinnately or palmately). Spring Cress (and other species in the genus) isn't classified as an Arabis sp. (Rock Cress) because of its wingless seeds; the seeds of Rock Cresses have winged membranous margins of varying widths.