Persicaria minor (Pygmy Smartweed)

Plant Info
Also known as: Small Water-pepper
Genus:Persicaria
Family:Polygonaceae (Buckwheat)
Life cycle:annual
Origin:Europe
Habitat:part shade, sun; moist disturbed soil; shorelines, ditches, waste places, agricultural fields
Bloom season:July - September
Plant height:6 to 14 inches
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 5-petals Cluster type: raceme Cluster type: spike

[photo of flowers] Slender, lax to tight spike-like clusters to 2 inches long at branch tips and arising from upper leaf axils. The lower part of the cluster often has gaps (interrupted) while the top of the cluster does not (uninterrupted). Flowers are about 1/8 inch long, pink with 5 tepals (petals and similar sepals).

Leaves and stems: Leaf attachment: alternate Leaf type: simple

[photo of leaves] Leaves are alternate, lance-linear, to 4 inches long and ½ inch wide, sharply pointed at the tip, toothless, hairless except for cilia-like hairs around the edges and sometimes on the major veins on the underside. The leaves are often darker and more blue-green than other members of the genus, lighter along the mid-vein, and lack a dark blotch on the upper surface. Leaves are stalkless or nearly so.

[photo of ocrea] At the base of the leaf, surrounding the stem, is a membranous sheath (ocrea) up to 1/3 inch long with pale ribbing and a fringe of bristly hairs about 1/8 inch long around the top edge. Stems are hairless, branched in the lower plant, often reddish, prostrate but rising up at the branch tips (decumbent) or ascending, often rooting at the nodes in the lower plant.

Fruit: Fruit type: seed without plume

Fruit is a shiny, smooth, brownish black to black seed, convex on both sides or rarely 3-sided.

Notes:

Pygmy Smartweed, formerly Polygonum minus, is a smaller, more spindly plant than other Smartweeds found in Minnesota and is a relative newcomer to our state. When we found it growing in our backyard strawberry patch, the first thought was: what is it? The narrow, blue-green leaves without a dark blotch didn't resemble any of the Persicaria species we were familiar with. The flower clusters are slender like Dotted Smartweed (P. punctata) but that never has pink flowers. We left it on the “to be IDed” list but a few weeks later found the same plant along the shore at Moore Lake in Anoka county. Rummaging through past images came up with more of this species from western Hennepin County taken a few years earlier. After much research we did discover its identity, and collected the specimen from Moore Lake as the second official record in Minnesota, the first being collected a month earlier at Edina High School. This is likely more widespread than the four sites we know about, and is probably more widespread than the national distribution map shows, but we suspect this is just another overlooked weed. If you've seen one Persicaria...?

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More photos

Photos courtesy Peter M. Dziuk taken in Anoka, Hennepin and Ramsey counties.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Sharon - Duluth Mn
on: 2015-10-26 15:45:29

This plant is definitely thriving only too well in Duluth.

Posted by: Jason H - Lino Lakes
on: 2017-10-06 11:45:10

I found this in a wetland restoration area in Lino Lakes, Anoka County. Saturated peaty soils over sand. Had to look it up. Thanks for including this species.

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