Persicaria punctata (Dotted Smartweed)
|Also known as:||Water Smartweed|
|Life cycle:||annual, short-lived perennial|
|Habitat:||part shade, sun; moist to wet; marshes, wet meadows, thickets, fens, lake shores, ponds|
|Bloom season:||July - September|
|Plant height:||12 to 30 inches|
|Wetland Indicator Status:||GP: OBL MW: OBL NCNE: OBL|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Slender, loosely spaced, erect to arching racemes, typically 2 to 4+ inches long at the tips of upper branches. Flowers are white to greenish, 1/8 inch long with 5 tepals (petals and similar sepals) that barely open and are mostly short stalked. The outside of the tepals are dotted with tiny glands (magnification may be required to see clearly).
Leaves and stems:
Leaves are alternate, narrowly lance to lance-elliptic, up to 6 inches long and ¾ inch wide, surfaces mostly hairless but covered with pitted dots (punctate) and a few scattered hairs along the lower midvein, the edges smooth except for short cilia-like hairs.
At the base of the leaf stalk is a membranous sheath (ocreae) that extends up around the branch stem, with pale ribbing and long bristly hairs on its upper edge, falling away with age. Stems are erect to spreading, simple or branching, smooth throughout and swollen just above the leaf nodes.
Fruit is a smooth, shiny, brownish black seed, 3-sided, more or less oblong and about 1/8 inch long.
Formerly called Polygonum punctatum, Dotted Smartweed is common and widespread in Minnesota, especially in our east central counties. Some of our smartweeds may be confused with each other but this species is quite unique with its narrow lance like leaves and slender, sparsely flowered racemes that are always white to greenish. It may be mistaken for the non-native Marsh Waterpepper (Persicaria hydropiper), which often has pinkish flowers in clusters that arise from the leaf axils, and dull brownish black seeds, where P. punctata flowers are never pink, are mostly at the stem tips, and has shiny seeds.
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Photos by K. Chayka taken in Ramsey County. Photos courtesy Peter M. Dziuk
Have you seen this plant in Minnesota, or have any other comments about it?