Polygonaceae

Thu, 02 Apr 2026 00:00:00 +0000

Polygonaceae (the buckwheat family) is a family of flowering plants in the order Caryophyllales, comprising approximately 1,200 species in 48 genera distributed across all continents except Antarctica. The family includes plants of major economic importance (buckwheat, rhubarb, sorrel), ecological significance (the invasive knotweeds), and pharmaceutical value (Japanese knotweed as a source of resveratrol).

The ochrea: defining character

The single most reliable diagnostic feature of Polygonaceae is the ochrea (plural: ochreae) — a tubular or funnel-shaped sheath formed from fused stipules that encircles the stem above each node. The ochrea is present in nearly all members of the family (reduced or absent in a few genera of subfamily Eriogonoideae) and is found in no other angiosperm family. When identifying an unknown plant, the presence of an ochrea at the stem nodes is strong evidence for Polygonaceae.

Reynoutria

Thu, 02 Apr 2026 00:00:00 +0000

Reynoutria Houtt. is a small genus of large, rhizomatous herbaceous perennials in the family Polygonaceae, native to East Asia. The genus contains the three species collectively known as the “knotweed complex” — Japanese knotweed (R. japonica), giant knotweed (R. sachalinensis), and their hybrid Bohemian knotweed (R. × bohemica) — which together constitute one of the most damaging groups of invasive plants in the temperate world.

Taxonomic history

The genus name Reynoutria was established by Maarten Houttuyn in 1777 for the species now known as Japanese knotweed. The subsequent taxonomic history is among the most confusing in angiosperm botany, involving at least three genera and dozens of name changes:

PlantTaxonomy on emsenn.net

Polygonaceae

The ochrea: defining character

Reynoutria

Taxonomic history