Persicaria - known also as Knotweed or Smartweed - is a genus of mainly annual, semi-evergreen, evergreen or herbaceous perennials that originate from a wide range of habitats worldwide. Knotweeds typically have simple leaves and long-lasting spikes of small bell-like - usually pink or white - flowers. Some species are cultivated as creeping ground cover and some for their autumn leaf colour. Some species however, can become invasive. Persicarias like moist soil and are happy in full sun or partial shade. Popular in borders and rock gardens, there is a species for almost every garden situation.