Persicaria pensylvanica laevigata
Smartweed family (Polygonaceae)
Description: 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 stems are round, smooth, light green to slightly red, and have a tendency to zigzag between the short narrow petioles of the leaves. The green to dark green leaves are up to 7" long and 3" across. They are lanceolate to broadly lanceolate, with smooth margins, and devoid of hairs on the lower and upper surfaces (for this variety). Unlike some introduced smartweeds, this plant has no darker markings on the upper surface of the leaves. At the base of the petioles are sheaths that wrap around the stem, which are devoid of bristles.
Some of the upper stems terminate in a short spike-like inflorescence about 2-3" long and narrowly cylindrical in appearance. It is normally more or less erect (unless the plant is leaning toward the light), and densely crowded all around with small buds and flowers about 1/8" across. These little flowers have 5 tepals that are white, light pink, or bright pink, and don't open widely even when they are in full bloom. There is no noticeable floral scent. The long peduncle of each inflorescence has small white hairs. The seeds are larger than those of most other smartweeds and spheroid in shape.
Cultivation: The preference is full or partial sun, moist conditions, and rich loamy soil. Standing water is tolerated if it is temporary. This robust plant is rather weedy and easy to grow it has more tolerance to drought than many other smartweeds. The leaves are rarely blemished by disease.
Range & Habitat: Pennyslvania Smartweed occurs in every county of Illinois, and is common (see Distribution Map). It can be found in moist black soil prairies, swamps, near ponds or lakes, edges of marshes, abandoned fields, moist areas along railroads and roadsides, vacant lots, fence rows, and other waste areas. This annual plant thrives on the reduced competition resulting from disturbance. It often forms colonies of varying size.
Faunal Associations: 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.
Photographic Location: The photographs were taken in a vacant lot near Urbana, Illinois.
Comments: This native plant, along with other members of the genus, is often undervalued because it is considered too common, and the flowers are not thought to be sufficient large and pretty. In fact, Pennsylvania Smartweed is rather attractive when the flowers are bright pink, and its ecological value to birds, moths, butterflies, and other insects, regardless of the color of the flowers, is quite high. Different varieties of this smartweed have been described by some authors; Persicaria pensylvanica laevigata is the most common variety in Illinois, which is distinguished from the others by the glabrous lower surface of its leaves. Distinguishing this smartweed from others is difficult. Pennsylvania Smartweed has the following features that may be helpful in making a correct identification as to species: 1) the leaves lack darker markings and are glabrous underneath (the latter trait applies to this variety only), 2) there are small hairs on the peduncle of each inflorescence, 3) the sheaths wrapping the stems at the base of the petioles have no bristles, and 4) the spikes of flowers are usually held more or less erect, rather than nodding. Other common names for this plant are 'Pinkweed' and 'Big-Seeded Smartweed.' Another scientific name for this plant is Polygonum pensylvanicum laevigatum.