PERSICARIA

Knotweed
Polygonaceae
Perennials

Sturdy plants with jointed stems and small white or pink flowers. Some kinds tend to get out of hand and need to be controlled.

Persicaria affinis

Himalayan native. Spreading plant to 1 ft. high, 2 ft. or more wide. Deep green, lance-shaped, finely toothed leaves are mostly basal; they grow 2–4 1/2 in. long, turn bronze in winter. Dense, erect, 2–3-in. spikes of bright rosy red flowers bloom in summer, early fall.

Persicaria amplexicaulis

Himalayan native. Forms a big clump to 4 ft. tall and wide when plants are in flower. Medium green leaves are pointed ovals up to 10 in. long. Blooms profusely from midsummer to fall, bearing narrow, 4-in. blossom spikes similar to those of lavender but in a wider range of colors—pink, purple, red, white.

Persicaria bistorta

Native to Eurasia. Makes aclump to 2 1/2 ft. high and 3 ft.wide, with large leaves. Tight,2–3-in. spikes of pale pink orwhite flowers bloom from latespring until well into summer.‘Superba’ is a good pinkselection.

Persicaria capitata

Himalayan native. Tough, trailing ground cover 3–6 in. high; spreads indefinitely both by rooting stems and by self-seeding. Oval, 1 1/2-in.- long leaves are dark green when new, take on pinkish overtones when mature. Leaves of all ages have a bronzy cast that deepens in cooler weather; they discolor and die below 28°F/–2°C. Stems and small, round flower heads are pink. Blooms almost all year in mild climates. Best in confined spots (where it won’t be able to spread) or in uncultivated areas. No irrigation needed.

Persicaria vacciniifolia

Himalayan native. Prostrate plant forms a foliage mat to 3 in. high, trailing to 2 ft. or wider. Slender, branching, reddish stems are clothed in oval, 1/2-in.-long, shiny green leaves that turn red in fall. In late summer, 6–9-in. flower stalks bear dense, upright, foxtail-like, 2–3-in. spikes of rose pink blossoms. Excellent as a bank cover or for draping over a boulder in a large rock garden.

Persicaria virginiana

Native to eastern North America, east Asia. To 2–4 ft. tall, spreading indefinitely by creeping rhizomes. Oval green leaves 3–10 in. long; insignificant flowers. The species is rarely found in gardens.