Lesser Swinecress (Coronopus didymus)
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Lesser swinecress (swinecress, wartcress) is a low growing or prostrate winter or summer annual and sometimes a biennial broadleaf plant. It is found throughout California to about 6600 feet (2000 m) and inhabits agricultural land and other disturbed areas. The leaves of lesser swinecress have an offensive, skunklike odor. Milk from dairy cattle feeding in infested fields has been reported to have an unpleasant flavor. Alfalfa hay palatibility is reduced when it contains high proportions of this weed. Lesser swinecress is problematic in newly planted alfalfa fields in the Sacramento, San Joaquin, and Imperial Valleys.
Alfalfa pastures, vegetable crop fields, orchards, nurseries, ditch banks, gardens, turf, roadsides, and other disturbed places.
Cotyledons (seed leaves) are hairless, narrowly lance shaped, have rounded tips and long tapered bases, and range from about 1/5 to almost 1/2 of an inch (5-12 mm) long. First and later leaves are alternate to one another along the stem, are divided into narrow segments, and resemble the cotyledons—except that their edges often have one or more rounded course teeth, and there are short hairs on the tips.
Young plants exist as rosettes until the flower stem develops at maturity.
Lesser swinecress grows in a prostrate or low-growing fashion. Stems may spread to almost 20 inches (0.5 m) along the ground but their tips tend to rise. Leaves are deeply lobed one to two times or deeply cut, but are not fully divided into leaflets (compound). They range from hairless to hairy and are about 3/5 to 3 inches (1.5–7 cm) long. Lower leaves grow on short stalks; upper leaves are stalkless and are alternate to one another along the stem.
Flowers bloom from February through October. Tiny, white, four-petaled, stalked flowers cluster along the flowering stem forming a flower head that is about 2/5 to 1-3/5 inches (1–4 cm) long. The flowering stems mostly arise from where the leaf stalk meets the main stem.
Fruits consist of a pod with a wrinkled surface that is about 1/16 of an inch (1.5 mm) long and up to 1/10 of an inch (2.75 mm) wide and has a short stalk. As it matures it develops two lobes. Within the Fruits are two chambers, each containing one seed.
Seeds are oblong to somewhat kidney shaped and remain inside the hardened fruit at maturity.
Reproduces by seed.
Related or similar plants
- Greater swinecress, Coronopus squamatus
- Mayweed chamomile, Anthemis cotula (before flowering)
- Redstem filaree, Erodium cicutarium (before flowering)