Persicaria maculosa (Lady's-thumb)

Plant Info
Also known as: Spotted Lady's-thumb, Redshank
Genus:Persicaria
Family:Polygonaceae (Buckwheat)
Life cycle:annual
Origin:Europe
Status:
  • Weedy
Habitat:part shade, sun; moist disturbed soil; shorelines, ditches, waste places, agricultural fields
Bloom season:June - September
Plant height:12 to 30 inches
Wetland Indicator Status:GP: FACW MW: FACW NCNE: FAC
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

Pick an image for a larger view. See the glossary for icon descriptions.

Detailed Information

Flower: Flower shape: 4-petals Flower shape: 5-petals Cluster type: raceme Cluster type: spike

[photo of flowers] Erect, densely packed spike-like racemes ½ to 2 inches long on smooth stalks at the tips of branches and the upper leaf axils. Clusters are mostly uninterrupted though occasionally a few flowers are separated at the base. Flowers are pink to deep purple, 1/8 inch long, usually with 4 (sometimes 5) tepals (petals and similar sepals) that barely open and are nearly stalkless.

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

[photo of leaves] Leaves are alternate, narrowly or broadly lance-shaped, usually with a dark blotch on upper surface, pointed at the tip, tapered or wedge-shaped at the base, typically 2 to 4 inches long (up to 7), and 1/3 to 1 inch wide, the stalk not more than 1/3 inch long, becoming stalkless in the upper plant. Leaf edges are toothless but with fine cilia like hairs or often rough when stroked towards the base. The surfaces are mostly smooth or with straight appressed hairs.

[photo of ocrea] At the base of the leaf stalk is a brown, membranous sheath (ocrea) with pale ribbing that extends up around the branch stem, tearing away with age, its upper edge with distinct bristly hairs about 1/8 inch long. Stems are green or red, erect to spreading or occasionally sprawling, simple or branching, smooth throughout or with soft appressed hairs on the upper branches. When sprawling, it may root at the nodes in the lower plant.

Fruit: Fruit type: seed without plume

Fruit is a dry seed (achene), disc shaped to 3-sided, brown or black with a smooth, shiny surface.

Notes:

Non-native Lady's-thumb, formerly Polygonum persicaria, has become widely established across North America and is one of the most common Smartweeds found in Minnesota. It can grow explosively in seasonal water basins, receding waterlines of lakeshores or any moist disturbed area, and at one time was designated a county-level noxious weed. It is similar to and can be difficult to distinguish from the native Nodding Smartweed (Persicaria lapathifolia) and more so Pennsylvania Smartweed (P. pensylvanica), both which share the same general habitats and have a number of overlapping characteristics. With the former, P. maculosa will have consistently shorter racemes that are mostly erect while P. lapathifolia will have longer and strongly nodding or dangling flower clusters. Like P. maculosa, P. pensylvanica also has shorter and more erect racemes but those of P. maculosa are typically a bit shorter and more slender. Also, the ocrea of P. maculosa has observable bristles or cilia fringe on the upper edge where the other two are usually fringeless, and P. maculosa will often have only 4 tepals and P. pensylvanica has 5. Lastly, both P. lapathifolia and P. pensylvanica occasionally have a darker spot on the upper leaf surface but P. maculosa almost always has a very dark spot present.

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More photos

Photos by K. Chayka and Peter M. Dziuk taken in Ramsey County.

Comments

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

Posted by: Mary Beth - Ottertail Co
on: 2015-06-11 11:05:33

I believe I have this in my garden(volunteer). Is there another one with pink flowers and the spotted leaf?

Posted by: K. Chayka
on: 2015-06-11 21:05:24

Most of the Persicaria species have a spot on the leaf. Look at the sheath and other parts of the plant to distinguish them.

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