Polygonaceae

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Knotweed family

Fallopia dumetorum from Thomé, Flora von Deutschland, Österreich und der Schweiz, 1885

Scientific classification

Kingdom:	Plantae
Division:	Magnoliophyta
Class:	Magnoliopsida
Order:	Caryophyllales
Family:	Polygonaceae Juss.

Subfamilies

Polygonoideae
Eriogonoideae

The family Polygonaceae, also known as the knotweed family or smartweed family, are a group of dicots, comprising about 50 genera and 1120 species of monoecious and dioecious herbs, shrubs and small trees. Some well known members include buckwheat, sorrel (but not wood sorrel), rhubarb, and knotgrass. The family is named for the shape of the seed; that of rhubarb, for example, has a triangular cross-section.

In the Cronquist system, the Polygonaceae were given their own order, but newer systems treat them as part of the Caryophyllales.

The family is present worldwide in temperate regions, with rare species found in the Tropics.

[edit] Taxonomy

There are 2 subfamilies:

The Polygonoideae is characterized by the lack of an involucre and the presence of ocreae (sheaths developed from stipules at the attaching leaves' bases). Some ocreas have mildly hairy fringes. This subfamily comprises about 28 genera and 800 species.
The Eriogonoideae, with about 330 species, is exclusive to the New World.