Bistorta affinis (D.Don) Greene

Kew Species Profiles

General Description

This mat-forming perennial with smooth leaves and spikes of small pink or red flowers was once admired in the Himalaya by Sir Joseph Hooker, one of Kew's early directors.

This perennial forms mats that creep over rocks and steep slopes in the central Himalaya. The fresh green leaves emerge in spring and the flower spikes develop in late summer, bearing numerous, small pink or red flowers. After the first frosts, the leaves turn red then chestnut-brown.

One of Kew's early directors, Sir Joseph Hooker, admired this species in the Himalaya, and described it 'hanging in rosy clumps from moist precipices'.

Species Profile

Geography and distribution

Native to the region from Afghanistan to Nepal and India and also in China (Tibet) at elevations up to 4,900 m.

Description

A creeping perennial that can form mats several metres across. The leaves are smooth, lanceolate or narrowly elliptic, bluish on the undersides and 3-8 cm long. The flowering stems are 5-25 cm long, with sheathing leaves at the base and dense flower spikes 5.0-7.5 cm long. The flowers are pale pink to red, five lobed and 4-6 mm across. Each flower has eight stamens and three styles. The fruit is a three-angled nutlet.

Uses

Persicaria affinis is cultivated as an ornamental and is widely available from commercial nurseries under this name or the synonym Polygonum affine . Cultivars include P. affinis 'Superba' (with red and pale pink flowers) and 'Donald Lowndes' (with pale to dark pink flowers). Both have received an Award of Garden Merit from the Royal Horticultural Society.

In the Garhwal Himalaya the flowers of knot weed are used as a stimulant, and in the Ladakh region of Jammu and Kashmir an extract of the root is used in traditional medicine against fever.

This species at Kew

Knot weed can be seen growing in the Woodland Garden surrounding the Temple of Aeolus, and in the Plant Family Beds at Kew. It can also be found in the Himalayan Glade at Wakehurst; these specimens were brought back and planted by Tony Schilling, who was Curator at Wakehurst between 1967 and 1991.

Distribution

China, India

Ecology

Rocky mountainsides, screes, glacial moraines, alpine pastures, wet meadows and river banks.

Conservation

Not evaluated according to IUCN Red List criteria.

Hazards

Apparently distasteful to grazing animals.

Use

Ornamental, traditional medicine.