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

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!

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.

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.

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.

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.