Persicaria Species, Lady's Thumb, Red Shank, Spotted Knotweed

Persicaria maculosa

Family: Polygonaceae
Genus: Persicaria (per-sih-KAR-ee-uh) (Info)
Species: maculosa (mak-yoo-LOH-suh) (Info)



Water Requirements:

Requires consistently moist soil; do not let dry out between waterings

Very high moisture needs; suitable for bogs and water gardens

Sun Exposure:

Sun to Partial Shade

Light Shade

Partial to Full Shade



Foliage Color:

Unknown - Tell us


12-18 in. (30-45 cm)


6-9 in. (15-22 cm)

9-12 in. (22-30 cm)


USDA Zone 4b: to -31.6 C (-25 F)

USDA Zone 5a: to -28.8 C (-20 F)

USDA Zone 5b: to -26.1 C (-15 F)

USDA Zone 6a: to -23.3 C (-10 F)

USDA Zone 6b: to -20.5 C (-5 F)

USDA Zone 7a: to -17.7 C (0 F)

USDA Zone 7b: to -14.9 C (5 F)

USDA Zone 8a: to -12.2 C (10 F)

USDA Zone 8b: to -9.4 C (15 F)

USDA Zone 9a: to -6.6 C (20 F)

USDA Zone 9b: to -3.8 C (25 F)

USDA Zone 10a: to -1.1 C (30 F)

Where to Grow:

Unknown - Tell us


Handling plant may cause skin irritation or allergic reaction

Bloom Color:



Bloom Characteristics:

This plant is attractive to bees, butterflies and/or birds

Bloom Size:

Unknown - Tell us

Bloom Time:

Mid Summer

Late Summer/Early Fall

Mid Fall

Other details:

May be a noxious weed or invasive

Soil pH requirements:

Unknown - Tell us

Patent Information:


Propagation Methods:

By dividing the rootball

By dividing rhizomes, tubers, corms or bulbs (including offsets)

From leaf cuttings

From herbaceous stem cuttings

From seed; direct sow outdoors in fall

From seed; winter sow in vented containers, coldframe or unheated greenhouse

Self-sows freely; deadhead if you do not want volunteer seedlings next season

Seed Collecting:

Bag seedheads to capture ripening seed

Allow seedheads to dry on plants; remove and collect seeds

Properly cleaned, seed can be successfully stored


This plant is said to grow outdoors in the following regions:

Merced, California

Glen Ellyn, Illinois

Newburgh, Indiana

Valparaiso, Indiana

Iowa City, Iowa

Derby, Kansas

Benton, Kentucky

Melbourne, Kentucky

Brookeville, Maryland

Cole Camp, Missouri

Cambridge, Ohio

Glouster, Ohio

Vermilion, Ohio

Portland, Oregon

Millersburg, Pennsylvania

Philadelphia, Pennsylvania

Wayne, Pennsylvania

Greenville, South Carolina

Clarksville, Tennessee

South Milwaukee, Wisconsin

show all

Gardeners' Notes:


On Aug 2, 2015, Rickwebb from Downingtown, PA wrote:

This annual weed, which is sort of pretty for a weed, is native across Eurasia. It was first found in America near the Great Lakes in the 1840's and since has spread through the whole continent. Back in Eurasia it probably is a good source of seed for birds, especially waterfowl, as the similar Pennsylvanian Smartweed that is native to North America is a good source of seed for birds, especially waterfowl, to feed on here. Otherwise, this is a very abundant weed that I pull out of the ground all the time in my gardens. It does not really cause a rash on my bare hands, but some people may experience that. It gets its name from a dark spot in the middle of the leaf that looks like a lady may have squeezed the leaf with her thumb. The leaves round out a little in the middle. It has a sheath a... read more


On Jul 1, 2013, plant_it from Valparaiso, IN wrote:

Spotted Lady's Thumb is not native to the U.S. and has become invasive, so it's a negative in my book.

Don't confuse Polygonum persicaria with the native Polygonum pensylvanicum. You can tell them apart from their ocreas. The ocrea is a thin membranous sheath that encircles the stem at the base of each leaf petiole. The ocreas of P. persicaria have small (2mm) stiff hairs arising from the top. The ocreas of the native P. pensylvanicum do not.

I posted a close up photo of Spotted Lady's Thumb where you can see the very small stiff hairs poking out of the ocreas.


On Feb 8, 2011, Nanth333 from Nottingham, MD wrote:

I don't grow it in my garden; but it's available along the road. I love the flowers and dry them and use them in my papermaking as inclusions. It's also a good addition to salads.


On Apr 29, 2009, KarenRei from Iowa City, IA wrote:

I would have rated this a strong negative -- it's a noxious weed that reseeds like it's going out of style and is nearly impossible to eradicate. *But*, last year I found a great use for it, which pushes it up to "neutral": it's a perfect distraction crop for Japanese Beetles. It doesn't seem to draw them to the garden (I didn't have any beetles for years even with the smartweed hanging about), but when they're there, as they were last year, they ate nothing but smartweed. In fact, they're the only insect I've found willing to eat the stuff. They pretty much skeletonize it and leave the rest of the garden alone.


On Aug 27, 2008, philotea from Philadelphia, PA wrote:

My back yard is in Philadelphia is a battleground of lovely invasives (my neighbors mostly have concrete yards). My groundcover is a mixture of persicaria maculosa threaded through violets with a few punctuations of spiderwort, pokeweed, persicaria odorata and morning glory up the fences. It's quite lovely and virtually maintenance free. Since they're all invasive, I don't really have to weed or water except in the Spring when other invasives come up. I do have to take a machete to the morning glory now and then, but I'm quite thrilled with the results. Birds and squirrels LOVE my yard. I make a couple of wood-mulch paths through the green, set up a chair, and enjoy!


On Sep 11, 2007, ladyannne from Merced, CA (Zone 9a) wrote:

Hard to get rid of!


On Sep 16, 2005, CaptMicha from Brookeville, MD (Zone 7a) wrote:

I know this as pinkweed.

I hate it, it grows everywhere, gets into everything and is just a pest. It especially likes disturbed soil so that if you weed or make new beds, you'll be sure to find it there.


On Jan 2, 2005, melody from Benton, KY (Zone 7a) wrote:

An invasive little weed that spreads rapidly in damp areas. It's cheerful and cute, but even the smallest piece of a stem is capable of producing a new plant. When removing it from an area, care must be taken to get every shred of the stuff....even then it will take several seasons to rid it completely from a planting space. It produces a vast number of seeds that can lay dormant for great lengths of time and still remain viable.

The name Smartweed comes from the sap that sometimes causes ittitation when it comes in contact with the skin.

The seeds are attractive to songbirds and wildlife, but there are many plants that are less invasive that can serve that purpose....and this stuff is never going to be put on any endangered list.