Crooked Run Valley
hairy bittercress (Cardamine hirsuta)
hairy wood cress
common bitter cress
SCIENTIFIC SYNONYMS: There are no scientific synonyms for Cardamine hirsuta.
TAXONOMY: The currently accepted scientific name for hairy bitter-cress is Cardaine hirsuta L.
NATIVE STATUS: Introduced.
GENERAL BOTANICAL CHARACTERISTICS:
Habit: This plant is a winter annual or biennial. Initially, it forms a low rosette of basal leaves spanning up to 8" across. From the center of a rosette, there develops a flowering stalk up to 10" tall that is unbranched or sparingly branched; this stalk is light green to dull purple and hairless, except for a few long hairs toward its base. About 3-5 cauline leaves alternate along the stalk.
Leaves: Each basal leaf is up to 4" long, ¾" across, and simple-pinnate, consisting of 5-9 leaflets and a long petiole. The basal leaflets are orbicular to oval in shape and slightly undulate along their margins; the outer leaflets are larger in size than the inner leaflets. The basal petioles often have a few long hairs along their margins and they are often dull purple. About 3-5 cauline leaves alternate along the stalk. The cauline leaves are similar to the basal leaves, except they are shorter in length and their leaflets are more narrow (linear-oblong to ovate-oblanceolate). Sometimes long hairs are present along the margins of the cauline leaflets and near the base of the cauline petioles.
Flowers: The central stalk (and any secondary stalks) terminates in a raceme of flowers. The flowers bloom near the apex of the inflorescence, while the seedpods develop below. Each flower is less than ¼" across, consisting of 4 white petals, 4 sepals, 4 stamens, and a pistil with a single style. The sepals are light green to dull purple, oblong in shape, and either hairless or slightly hairy; they are shorter than the petals.
Fruit/Seeds: Each flower is replaced by a narrowly cylindrical seedpod (silique) up to 1" long. The seedpods are light green to dull purple, hairless, and ascending; they have stout pedicels up to ½" long. Each seedpod contains several small seeds that are ovoid, somewhat flattened, and wingless along their margins. One bittercress plant can produce five thousand seeds which have no dormancy requirement and can germinate quickly.
Roots: The root system is shallow and fibrous.
REGENERATION PROCESS: Hairy bittercress propgates itself by reseeding.
HABITAT TYPES: Habitats consist of cropland, old fields, margins of paths, roadsides, and waste areas. Open habitats with a history of disturbance are preferred.
SITE CHARACTRISTICS: Hairy bittercress prefers full to partial sunlight, moist to mesic conditions, and a somewhat barren soil containing gravel or clay. However, it will adapt to fertile loam and sandy soil as well. Most growth and development occurs during the early spring when temperatures are cool and moisture is abundant.
SEASON DEVELOPMENT: The blooming period occurs from early to mid-spring and lasts about a month.
GENERAL DISTRIBUTION: Hairy bittercress has been reported from the Atlantic Coast states south to Florida, and west across the Gulf Coast states into the Southwest and the far Pacific Coast states. It is generally absent from the Great Plains and Roky Mountain states. It also occurs in the Canadian provinces of Ontario, Quebec, Prince Edward Island, and British Columbia.
SKY MEADOWS DISTRIBUTION: To be determined.
IMPORTANCE AND USES: The nectar and pollen of the flowers probably attract small bees and flies. The caterpillars of the butterfly Anthocharis midea (falcate orangetip) and the moth purple-backed cabbageworm (Evergestis pallidata) feed occasionally on Cardamine spp.
Hairy bittercress is considered a nuance weed. It commonly grows in the potting media of container-grown ornamentals and often through drainage holes in nursery containers. It also can be a problem in propagation houses, greenhouses, and in the field. In cases where environmental conditions are not conducive to germination, bittercress seed can remain viable in the soil or potting for several years. Bittercress seeds are small and sticky when wet, making them prone to sticking to the sides of empty containers or being transported on shoes or clothing of nursery employees. Upon germination, bittercress can reach maturity and begin flowering and seeding in as little as five weeks under favorable conditions. Bittercress is a known host for other common nursery pests including whiteflies, mites, and some diseases.