Photo by Melody

PlantFiles: Smartweed, Big Seeded Smartweed, Pink Knotweed, Pinkweed, Pennsylvania Smartweed
Persicaria pensylvanica

Family: Polygonaceae
Genus: Persicaria (per-sih-KAR-ee-uh) (Info)
Species: pensylvanica (pen-sill-VAN-ee-ka) (Info)

Synonym:Polygonum bicorne
Synonym:Polygonum mexicanum
Synonym:Polygonum mississippiense
Synonym:Polygonum pensylvanicum
Synonym:Persicaria mississippiensis

5 members have or want this plant for trade.


36-48 in. (90-120 cm)

18-24 in. (45-60 cm)

Not Applicable

Sun Exposure:
Full Sun
Sun to Partial Shade
Light Shade

Handling plant may cause skin irritation or allergic reaction

Bloom Color:
Pale Pink

Bloom Time:
Late Spring/Early Summer
Mid Summer
Late Summer/Early Fall


Other details:
May be a noxious weed or invasive
This plant is attractive to bees, butterflies and/or birds
Self-sows freely; deadhead if you do not want volunteer seedlings next season

Soil pH requirements:
4.5 or below (very acidic)
4.6 to 5.0 (highly acidic)
5.1 to 5.5 (strongly acidic)
5.6 to 6.0 (acidic)
6.1 to 6.5 (mildly acidic)
6.6 to 7.5 (neutral)
7.6 to 7.8 (mildly alkaline)
7.9 to 8.5 (alkaline)

Patent Information:
Unknown - Tell us

Propagation Methods:
From seed; direct sow outdoors in fall
From seed; winter sow in vented containers, coldframe or unheated greenhouse
From seed; stratify if sowing indoors

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

Click thumbnail
to view:

By melody
Thumbnail #1 of Persicaria pensylvanica by melody

By melody
Thumbnail #2 of Persicaria pensylvanica by melody

By melody
Thumbnail #3 of Persicaria pensylvanica by melody

By htop
Thumbnail #4 of Persicaria pensylvanica by htop

By htop
Thumbnail #5 of Persicaria pensylvanica by htop

By htop
Thumbnail #6 of Persicaria pensylvanica by htop

By htop
Thumbnail #7 of Persicaria pensylvanica by htop

There are a total of 16 photos.
Click here to view them all!


1 positive
2 neutrals
3 negatives

Gardeners' Notes:

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

Polygonum pensylvanicum is native to the U.S. and I can't get enough of the beautiful flowers, so it's a positive in my book.

Don't confuse this native plant with Polygonum persicaria. P. persicaria is a non-native invasive. 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.

Negative KyWoods On Jul 9, 2011, KyWoods from Melbourne, KY (Zone 6a) wrote:

I thought these were pretty when they showed up in one area, so I let them stay. Big mistake--now I am pulling them up everywhere! If you want these in a small area, make sure you pluck off the flowers before they go to seed!

Neutral NatureLover1950 On Feb 28, 2009, NatureLover1950 from Vicksburg, MS (Zone 8a) wrote:

I like to find this weed when it's flowering in local fields. When the flowers are at the pink stage I clip a big bunch to use in dried flower arrangements. They not only dry well but hold their color very well.

Negative CaptMicha On May 24, 2005, CaptMicha from Brookeville, MD (Zone 7a) wrote:

Me no likey.

This plant is a pest in recently disturbed earth, which means any new gardens or freshly dug up gardens.

Also pops up in the lawn.

Neutral JodyC On Jan 17, 2005, JodyC from Palmyra, IL (Zone 5b) wrote:

This native annual plant is 1-4' tall, branching occasionally. It is more or less erect, often bending toward the light in partially shaded locations.

The flowers attract many kinds of insects, including long-tongued bees, short-tongued bees, wasps, flies, small butterflies, skippers, and moths. Almost all of these insects seek nectar. The caterpillars of several moths feed on the foliage of this smartweed and others, including Lithacodia synochitis (Black-Dotted Lithacodia), Lithacodia carneola (Pink-Barred Lithacodia), Haematopsis grataria (Chickweed Geometer; often flies during the day), and Dipteryia rosmani (Noctuid Moth sp.). The caterpillars of the butterflies Lycaena helloides (Purplish Copper) and Strymon melinus (Gray Hairstreak; eats flowers & buds) are occasionally observed on smartweeds as well. The rather large seeds are very popular with various bird species, including waterfowl, upland gamebirds, and songbirds (see Bird Table). Many of the wetland birds have not been listed in the table. It is possible that the seeds are only partially digestible, and thus some of them may be distributed by these birds. Because the leaves are somewhat bitter and peppery, this plant is not a favored food source for mammalian herbivores.

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

An invasive weed that has the ability to reproduce itself from even the tiniest bit of stem. It grows in cultivated fields, gardens and damp meadows. Vast amounts of seeds are produced that have the capability of remaining dormant for quite some time.

The seeds are attractive to birds and wildlife, but so many of these plants are produced each year, there is no need to propogate it on purpose.

The sticky sap can cause irritation if it comes in contact with the skin, thus, the name Smartweed.


This plant has been said to grow in the following regions:

Prescott Valley, Arizona
Deer, Arkansas
New Milford, Connecticut
Demorest, Georgia
Leavenworth, Kansas
Benton, Kentucky
Melbourne, Kentucky
Brookeville, Maryland
Cumberland, Maryland
Vicksburg, Mississippi
Ogdensburg, New York
Orient, Ohio
San Antonio, Texas

We recommend Firefox
Overwhelmed? There's a lot to see here. Try starting at our homepage.

[ Home | About | Advertise | Media Kit | Mission | Featured Companies | Submit an Article | Terms of Use | Tour | Rules | Privacy Policy | Contact Us ]

Back to the top

Copyright © 2000-2015 Dave's Garden, an Internet Brands company. All Rights Reserved.

Hope for America