Persicaria lapathifolia (Nodding Smartweed)

Plant Info
Also known as: Pale Smartweed, Curlytop Knotweed
Family:Polygonaceae (Buckwheat)
Life cycle:annual
Habitat:part shade, sun; moist; ditches, floodplains, waste areas, fields, shorelines
Bloom season:July - September
Plant height:2 to 6 feet
Wetland Indicator Status:GP: OBL MW: FACW NCNE: FACW
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] Densely packed, nodding spike-like racemes, typically 2 to 4 inches long (or longer!) and about ½ inch in diameter, mostly at the tips of stems, sometimes in upper leaf axils of branches. Flowers are greenish white to pink, 1/8 long with 4 or 5 tepals (petals and similar sepals) that barely open, and nearly stalkless. The stalk of the raceme can be smooth or covered in glandular hairs.

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

[photo of leaves] Leaves are alternate, lance-like, up to 8 inches long and to 2 inches wide, widest near the base with a rounded taper to the short stalk, and a long, even taper to a sharp tip. Sometimes there is a dark blotch on the upper surface but usually not, the stalk up to 5/8 inch long. Edges are toothless but have short, cilia-like hairs. Surfaces have inconspicuous translucent pits (punctate), are smooth or with matted, woolly hairs especially underneath or along the main veins, particularly when young.

[photo of ocrea] At the base of the leaf stalk is a membranous sheath (ocrea) that extends up around the stem and is typically prominently ribbed, its upper edge smooth (no bristles or fringe) or torn, becoming dark rusty brown and peeling with age. Stems are erect to spreading, densely branched, glossy smooth, green or often red and swollen just above the leaf axils.

Fruit: Fruit type: seed without plume

Fruit is a smooth, dry seed about 1/8 inch long, brown to black, shiny or dull, usually disc shaped.


Nodding Smartweed, formerly known as Polygonum lapathifolium, is native to both the eastern and western hemispheres and in North America a mix of both native and non-native ecotypes is likely present. In Minnesota it is arguably the largest of the smartweeds and can most easily be distinguished from other Smartweeds by its long, drooping flower clusters. A somewhat weedy species, it's common throughout the state, quickly filling in receding water lines of shallow marsh areas, disturbed road ditches, urban retention ponds and rural flood basins.

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More photos

Photos by K. Chayka taken in Pope and Ramsey counties. Photos courtesy Peter M. Dziuk taken in Anoka, Pope and Ramsey counties.


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

Posted by: Tamia - Zimmerman
on: 2014-08-10 11:56:51

My home is located across from the Sherburne Nat'l Wildlife Refuge.

Posted by: Bill - Pennington County
on: 2015-07-26 12:58:58

Another great plant for native bees and honey bees.

Posted by: Tom Ihlenfeldt - Saint Paul
on: 2019-10-11 16:37:05

As best as I & the Seek App can tell, I have this growing on my property. I wasn't sure if it was good for pollinators, but it sounds as if it is. Nice to have a preferred plant volunteer for my garden like this!

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