BUCKWHEAT FAMILY (Polygonaceae)
Common Persicaria, Pink Knotweed, or Jointweed; Smartweed
Polygonum pennsylvanicum
Flowers--Very small, pink, collected in terminal, dense, narrow obtuse spikes, 1 to 2 in. long. Calyx pink or greenish, 5-parted, like petals; no corolla; stamens 8or less; style 2-parted. Stem: 1 to 3 ft. high, simple or branched; often partly red, the joints swollen and sheathed; the branches above, and peduncles glandular.Leaves: Oblong, lance-shaped, entire edged, 2 to 11 in. long, with stout midrib, sharply tapering at tip, rounded into short petioles below.
Preferred Habitat--Waste places, roadsides, moist soil.
Flowering Season--July-October.
Distribution--Nova Scotia to the Gulf of Mexico; westward to Texas and Minnesota.
Everywhere we meet this commonest of plants or some of its similar kin, the erect pink spikes brightening roadsides, rubbish heaps, fields, and waste places, from midsummer to frost. The little flowers, which open without method anywhere on the spike they choose, attract many insects, the smaller bees (Andrena) conspicuous among the host. As the spreading divisions of the perianth make nectar-stealing all too easy for ants and other crawlers that would not come in contact with anthers and stigma where they enter a flower near its base, most buckwheat plants whose blossoms secrete sweets protect themselves from theft by coating the upper stems with glandular hairs that effectually discourage the pilferers.
Shortly after fertilization, the little rounded, flat-sided fruit begins to form inside the persistent pink calyx. At any time the spike-like racemes contain more bright pink buds and shining seeds than flowers. Familiarity alone breeds contempt for this plant, that certainly possesses much beauty. The troublesome and wide-ranging weed called lady's thumb is a near relative.
