Persicaria amplexicaulis Blackfield - Mountain Fleece

Persicaria amplexicaulis 'Blackfield' is a new knotweed with spikes of deep red flowers of rare intensity.

Called smartweed, knotweed or formerly Polygonum, Persicaria amplexicaulis 'Blackfield' has Himalayan origins that give it incredible hardiness and ease of cultivation. A very floriferous perennial, it produces numerous spikes 7 to 10cm (3 to 4in) long composed of small black buds that open into intense deep red flowers. The flowering is continuous throughout summer and can reach a height of 80cm (32in) at maturity.

The semi-evergreen, lanceolate leaves measure 15 to 25cm (6 to 10in) long. They are medium green in colour, turning red in autumn. Thanks to its spreading habit, the plant can be used as a ground cover.

It grows in the sun but appreciates bright partial shade. It likes rich and heavy soils, even very moist ones, and can be grown independently on sunny pond banks or in a cool and partially shaded understory at the base of trees.

It suits both contemporary gardens and wild-looking gardens, forming beautiful autumn scenes with grasses like miscanthus, molinias, and panicums.