Persicaria
Herbs, stems erect, ascending, creeping, procumbent or trailing with swollen nodes. Leaves simple, alternate or spiral. Ocreae a tubular sheath. Inflorescence with a partial racemose, spicate and capitate, determinate, bisexual. Flowers in an ocreola, tepal united at base, 4–5-merous, in two series, often persisted in fruit, glandular nectaries present. Stamens 6–8, filaments base adnate with tepal, anthers dorsifixed. Ovary with 2–3 clefted styles. Fruits lenticular, triangular or slightly circular.
About 150 species from northern temperate regions of the world, the West Indies and tropical South America. Twenty three species and 27 taxa are recognised in Thailand.