The spotted knotweed â_x0080__x0092_ small and reliable
"The most well-known knotweed species is probably the spotted knotweed (Bistorta affinis)," says horticultural technician Andre Stade. This ground cover grows 10 to 20 cm tall and forms dense, low mats. It blooms from July until frost, as the whitish, club-shaped inflorescences change color from pink to dark red to brown during flowering, and rebloom repeatedly. "It thrives in partial shade in combination with woody plants," explains the perennial expert. "Gardeners should avoid dry, hot spots, as the spotted knotweed doesn't like that." Leaving the leaves on the ground in autumn provides additional frost protection, and the plants survive the winter well. Among the spotted knotweed, the Bistorta affinis 'Superbum' variety is a tried-and-true variety that initially has white flowers that later turn deep red, and in autumn, the foliage turns orange-red. It doesn't overgrow and combines beautifully with meadow iris (Iris sibirca). For a compact variety, Stade recommends the 'Darjeeling Red' variety, which grows only 15 to 20 cm tall, or the even shorter 'Dimitry' variety. The flowers of both varieties are initially pinkish-red and later turn deep dark red as they fade, thus retaining their attractiveness until frost.
Some knotweeds are colorful
Persicaria filiformis 'Variegatum' is a very striking knotweed species. Its yellow, green, and brown-red spotted leaves look as if red, white, and brown had been painted onto green leaves with a brush. This ornamental foliage plant brings color to even dark corners of the garden from spring through autumn. In summer, the leaves' coloring is particularly intense. Persicaria filiformis grows to approximately 70 cm tall, grows vertically upwards, and is completely uncomplicated. From September to October, the delicate, red, thread-like spike flowers appear, dancing gracefully above the foliage. "Cover the plant with some brushwood for protection in winter," advises Stade.
