Dryas drummondii

16/50

(Yellow mountain-avens)

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Photo of Dryas drummondii by Jacob Frank

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Yellow mountain-avens is a dwarf shrub, forming dense mats in gravelly floodplains from the lowlands into the lower alpine zone in Denali. Growing from trailing woody stems, this species forms low mats reaching 2-15 cm. Its leathery leaves are elliptic, sometimes oblong or obovate, and wavy crenate-margined. Leaves are dark green above and densely white hairy (tomentose) below, the margins inrolled. The leaf bases are wedge-shaped - as opposed to rounded or notched bases in other species. Mats have persistent leaf bases and flowering stalks from the earlier season. The flowers have 8-10 yellow petals, and densely glandular-hairy sepals. There are many yellow stamens with hairy filaments and many plumose styles. Flowers always appear half-closed and nod when in bloom. Its fruits are a group of unfused achenes, attached to long styles covered in feathery white hairs, to facilitate wind dispersal. The heads face upwards when in fruit, the styles initially twisted together. Yellow mountain-avens - the only yellow-flowered Dryas species - is easy to recognize early in season, when it is in flower, but more difficult to distinguish from other Dryas species when fruiting. However, it is found almost always in dense mats on early-successional floodplains whereas other Dryas species usually occur in tundra (or open forest) and the leaf bases of yellow mountain-avens are a different shape.

Though its phenology depends on many environmental variables, generally speaking Dryas is an early-flowering group of species. The leaves are semi-evergreen, lasting a few seasons before senescence.

Dryas drummondii is a monoecious species with bisexual flowers. Species of Dryas are usually obligately out-crossing and dependent on insect pollinators, but the reproductive biology of yellow mountain avens has not been studied. The fruits are many small achenes, each attached to a long feather-like style, which can catch the wind and be carried short distances. Plants are fertile after ca. five years, with approximately 150 fruits per head (Lawrence et al. 1967). D. drummondii also grows clonally, forming large mats.

Yellow mountain avens is a North American endemic species, ranging from central Alaska to the Northwest Territories, southward to Washington, Idaho and Montana in the west. This species has disjunct populations in the East in Quebec, Ontario and Newfoundland. Dryas drummondii occurs primarily in the eastern half of the state in suitable gravel bar habitat from the Arctic slope southward to the glacial rivers of the southeastern panhandle. In Denali (as elsewhere), yellow mountain avens occurs primarily along rivers, with a few alpine localities, occurring on both sides of the Alaska Range.

Details are shown in the Plots & Charts found at right, depicting recent Denali data.

Yellow mountain avens is almost always found on areas without any incline. It occurs at a wide range of elevations, occurring from 120 to 1182 meters in the Park. It is most common on lower elevations.

Details are shown in the Plots & Charts found at right. For more on how to interpret these figures, visit Understanding Data Presented.

The species is found on gravelly floodplains, streambeds and moraines. The genus Dryas prefers calcareous base material (Cody 2000).

Dry to moist sites on river bars.