The Polygonaceae are herbs, shrubs, or rarely trees comprising about 30 genera and 1,000 species. The leaves are simple, alternate or rarely opposite, and usually stipulate. The membranous, sheathing stipule is called an ocrea. The flowers are actinomorphic, usually small, and are bisexual or occasionally unisexual. The perianth is usually in two undifferentiated whorls comprising 3-6 distinct or basally connate tepals. The androecium consists of 6-9, commonly 8 distinct or basally connate stamens, usually in two whorls. The gynoecium consists of a compound pistil of usually 3 carpels, an equal number of style branches or styles, and a superior ovary with one locule containing a single basal ovule. The fruit is usually a 3-angled or 3-winged achene.

Each "thumbnail" image below is linked to a larger photograph.

Antigonon leptopus, Mexican creeper. Although the flowers of this coarse vine are showier than average for Polygonaceae, a closer view (below) reveals that their construction is quite typical for the family, note 5-parted perianth and eight stamens.
Coccoloba uvifera, sea grape. Unusual in the family, this tree species also has small, greenish flowers with a 5-lobed perianth, 8 stamens, and 3 or occasionally 4 styles. The fruits are edible and made into jelly.
Eriogonum compositum, northern buckwheat, Mt. Spokane, WA, 2003.
Eriogonum sp., wild buckwheat. This example has six perianth segments and nine stamens.
Homalocladium platycladum, ribbon bush. This photo shows a cluster of flowers at one of the nodes of the flattened, photosynthetic stem. The leaves are reduced to tiny brownish scales. Small greenish flowers such as these are common in the family. In this species the perianth is 5-lobed but 8 stamens are present. Careful inspection of the lower flower may reveal three style lobes.
Muehlenbeckia axillaris, Note unisexual flower (female).
Polygonum aviculare, knotweed. This species illustrates the membranous sheathing stipules or ocreae found in this family.

Polygonum convolvulus, wild buckwheat, black bindweed, Avery Park, Corvallis, OR, Jul 2004.
Polygonum newberryi, knotweed. The reddish ocreae are clearly visible in the photo on the left.
Polygonum punctatum, dotted water smartweed, Avery Park, Corvallis, OR, Jul 2004.  Note sheathing stipule (ocrea) with marginal bristles.
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Rumex albescens, hu'ahu'ako. The female flowers of this monoecious Hawaiian endemic species have 3 feathery stigmas.

Rumex crispus fruits
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Rumex skottsbergii, pawale, endemic to Hawaii.
Triplaris surinamensis, longjohn. This is another of the exceptional trees in the Polygonaceae. The green arrows in the photo on the left point to a male tree in the foreground and the red arrows to a female tree of this dioecious species in the left background. Pistillate flowers and developing 3-winged fruits can be seen in the third photo while male inflorescences are shown in the second photo.

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