Rorippa palustris (Bog Yellow-cress)
|Also known as:||Marsh Yellow Cress|
|Life cycle:||annual, short-lived perennial|
|Habitat:||part shade, sun; wet ditches, wet meadows, along shores, swamps, mud flats|
|Bloom season:||May - September|
|Plant height:||12 to 40 inches|
|Wetland Indicator Status:||GP: OBL MW: OBL NCNE: OBL|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Elongating clusters at the end of branching stems and arising from the leaf axils, with a small compact flower head at the tip and fruit developing below it. Flowers are less than ¼ inch across with 4 yellow spatula-shaped petals about 2 mm long alternating with 4 yellowish-green oblong sepals that are about as long as the petals. 6 yellow stamens and a stout style are in the center
Leaves and stems:
Leaves are somewhat variable, 2½ to 8 inches (6 to 20+ cm) long, lance-oblong to egg-shaped in outline, coarsely toothed and may be hairy or hairless. Basal leaves are stalked; basal and lower leaves usually have a few to several deep, narrow lobes and a large lobe at the tip end. Stem leaves become smaller, less lobed, and stalkless or nearly so in the upper plant. Stems are erect to ascending, usually branched in the upper plant, green or tinged red, hairy or hairless.
Fruit is a cylindrical pod up to about 3/8 inch (3 to 10 mm) long, straight to slightly curved, bulging with the developing seed, and the remains of the style persisting at the tip. The stalks are held straight out, with the pod usually angled up slightly.
There are 2 subspecies of Bog Yellow-cress found in Minnesota: subsp. hispida, with hairy leaves and stems, and subsp. palustris, which is hairless throughout. While the flowers are similar to some Descurainia (tansy mustard) species, their finely divided, more feathery leaves and slender, longer pods are different enough to distinguish them from Bog Yellow-cress.
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- Bog Yellow-cress plant
- Bog Yellow-cress plant
- unbranched plant
- early growth, basal rosette
- subsp. palustris is hairless
- subsp. hispida has hairy stems and leaves
- close-up of flowers
- a pollinator
Photos by K. Chayka taken in Ramsey, Scott and Stearns counties. Photos by Peter M. Dziuk taken in Anoka and Dakota counties.
Have you seen this plant in Minnesota, or have any other comments about it?