Knot weed, Smart weed, Fleece flower

Annuals, herbaceous perennials and shrubby climbers. Occasionally aquatic plants. Leaves are simple with entire margins. Flowers are small but sometimes in showy clusters. Flowers commonly white, reddish or greenish.


Ornamentals. Sometimes invasive.


Prefers a rich, moist fertile soil, but many are hardy in poorer soils. Grow in full sun or shade. Need irrigation in dry weather, Mulch annually in early spring with rotted manure or compost.


Division in spring or autumn, softwood cuttings in spring. Also grows readily from seed.


Around 150 species and many cultivars including:

P. bistorta – broad leaves at base of upright stems to 50cm tall. Cylindrical pink flower spikes in spring.

P. odoratum (Vietnamese Mint) – to 30cm tall. Edible hot-tasting foliage which may be used in cooking.

Plant Health

Minimal pest and disease problems; occasionally attacked by pests including beetles.

More info

From many temperate regions including United States, Britain, Europe, Asia and Japan.