(hoary yellowcress)
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Rorippa barbareifolia is an annual herb with yellow flowers in the mustard family (Brassicaceae) typically found in wet areas in the lowlands such as streambanks, thermokarst pits and lakeshores. Plants grow 30-70 cm tall. Basal leaves are
compound,
lyrate-
pinnate, the margins irregularly
serrate. Stem leaves are sessile,
lanceolate in outline, irregularly
serrate, lower leaves are typically
pinnate, and becoming
lobed higher up the stem. Stems are densely hairy below, becoming
glabrous higher up the stem. The flowers are arranged in large
racemes borne both terminally and in the
axils of stem leaves. As with all members of the mustard family the
perfect (bisexual) flowers have 4 petals, 4
sepals and 6
stamens. Petals are yellow, 1.8-3.5 mm long. The silicles (seed pods) are round,
glabrous, and 4-valved, 3.5-5.7 mm long.
Rorippa barbareifolia could potentially be confused with
Barbarea orthoceras, another tall yellow-flowered mustard with
lyrate leaves, but that plant has seedpods that are long and narrow, not round.
This species flowers early to mid-summer. Seeds usually germinate in the late-summer-fall.
R. barbareifolia is
monoecious, and insect pollinated. Seeds are water and gravity disseminated.
Rorippa barbareifolia is an amphi-Beringian species with a boreal-montane distribution. In North America, this species occurs in Alaska, Yukon, B.C. and Northwest Territory. In Alaska, it ranges across much of the boreal region of the state, but is absent in the Arctic, Alaska peninsula/Aleutian chain, and the southeastern panhandle. In Denali, this species occurs in widely scattered localities in the wet lowlands north of the Alaska Range.
Details are shown in the Plots & Charts found at right, depicting recent Denali data.
R. barbareifolia is only found a handful of times in Denali at elevations from 137 m to 619 m, with an average elevation of 304 m. It is usually found on flat sites (average slope=3.3 degrees).
Details are shown in the Plots & Charts found at right. For more on how to interpret these figures, visit Understanding Data Presented.
This species typically grows in disturbed areas such as muddy/silty floodplains, gravel bars, and roadsides.
Wet to moist sites.
