(Soják) Soják
Description
Argentina aristata is a dwarf cushion-forming herb of the high alpine zone of the Himalaya, native to Nepal, Bhutan, China, India and Pakistan, with around 75 documented occurrences confined to elevations above the tree-line. It grows on stony alpine turf, gravelly slopes, fellfield and the crevices of moraine and rock outcrops, typically between about 3800 and 5000 m. The photographed plant was recorded along the historic Ludlow-Sherriff Trail at Shashuna in Bhutan at 4000 m, flowering in June, when the brief high-altitude growing season permits these tightly clustered alpines to bloom.
The species is a densely tufted, mat-forming perennial with a stout, branched, woody caudex clothed in the persistent remains of old leaves. The leaves are imparipinnate and crowded into rosettes, with small, deeply incised to pinnatifid leaflets that are silky-villous, the segments often ending in a fine bristle-like point, as the epithet aristata implies. The flowers are solitary or few on short scapes; they are typically pentamerous with an epicalyx, the petals golden-yellow and obovate, exceeding the sepals, surrounding numerous stamens and a head of carpels. The fruit is a cluster of small dry achenes.
Argentina is segregated from Potentilla in the broad sense, comprising the silverweeds and allied pinnate-leaved cinquefoils; this taxon was long known as Potentilla microphylla var. achilleifolia before transfer by Soják. Such cushion habit is a classic adaptation to the cold, windswept, desiccating conditions of the upper alpine zone. The species is restricted in range but locally frequent in suitable high-altitude habitat and is not considered threatened.
Author: (Soják) Soják · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, Potentilla monograph (Soják)