(Ross' avens)
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Photo of Geum rossii by Eric Groth
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Geum rossii is a charismatic alpine plant in the rose family (Rosaceae) with glossy pinnately divided leaves and bright yellow radially-symmetrical flowers. Plants form tufted clumps from a thick caudex in wet areas, meadows, snowbeds, and mossy ericaceous tundra, growing 10-25 cm high. Reddish brown dead leaves persist at the base of the plant for more than one season. Leaves are all basal, divided into many segments. Each segment is two or three
lobed, glossy green on the upper side and paler beneath. The flowering stalks are leafless save for a few
bracts right below the blossoms. The stems and leaves are hairless or sparsely short-hairy.
Geum rossii has one to several
perfect flowers on each stem, the five yellow petals about 1 cm long. The fruits are hairy
achenes, gradually tapering into a straight
style, 5-7 mm long, each containing a single seed. This species may be confused with
Geum glaciale, which is however quite rare in Denali and is much hairier with larger flowers, or with
G. macrophyllum, which is a taller plant that grows in forests and has large,
lobed leaflets at the tips of the leaves.
The phenology of
Geum rossii has been much studied in Colorado, where it is a common alpine tundra plant. A summary of past studies as well as an investigation of its growth in five habitats over six years can be found in
. Snow melt or soil temperature cues flowering, and flowering occurs shortly after the snow melts. Flowering stems grow rapidly, blooming before leaves are completely expanded (
Spomer and Salisbury 1968). The stalks turn reddish after blooming.
G. rossii develops its leaves and flowers as buds two years before they open (
Meloche and Diggle 2001). Buds are grown as primordia over one season, persist through the next summer as a new set of primordia is developed, and finally expand out of the ground in their third year. The mature leaves and flowering stalks last only for one season, and then senesce. In Denali this species usually flowers right after snow melt.
Plants produce large, bisexual yellow flowers, which are likely insect pollinated. Seeds are spread via gravity. The species also spreads vegetatively, growing from a branched
rhizome (
Spomer and Salisbury 1968).
Geum rossii is an amphi-Beringian species with an arctic-alpine distribution. Geum rossii occurs from Chukotka and Kamchatka in the west eastward to Yukon Territory in North America. There are also disjunct populations of this species in the southern Rocky Mountains, occurring from western Montana to Arizona and New Mexico. In Alaska, Geum rossii occurs in alpine areas from the Brooks Range southwards to the White, Alaska Range and Wrangell Mountains into the Alaska Peninsula and Aleutian chain and the St. Elias Mountains in northern southeast Alaska. In Denali, G. rossii occurs primarily north of the Alaska Range crest and extending into the upper Chulitna and Yentna river drainages to the south.
Details are shown in the Plots & Charts found at right, depicting recent Denali data.
Geum rossii is a species of high elevations, most frequent above 1100 meters. It is more common on moderate slopes (12-20 degrees incline), and has a strong preference for north-facing aspects.
Details are shown in the Plots & Charts found at right. For more on how to interpret these figures, visit Understanding Data Presented.
Wide-ranging; wet to somewhat dry sites in the mountains.
