Redshank (Plants of the Peggy Notebaert Nature Museum Grounds, Chicago, Illinois)

Redshank

Persicaria maculosa

Summary ⁶

Persicaria maculosa (syn. Polygonum persicaria) is an annual plant in the knotweed family, Polygonaceae. Common names include lady's thumb,spotted lady's thumb, Jesusplant, and redshank. It is native to Eurasia and present as an introduced and invasive species in North America, where it was first noted in the Great Lakes region in 1843.

Description ⁷

This annual plant is about ½–2' tall and more or less erect, although individual plants may sprawl. The stems are usually light green, round, and glabrous or slightly pubescent. The alternate leaves are up to 6" long and 1" across, although usually smaller. They are lanceolate or linear-lanceolate, hairless, smooth along the margins, and sometimes slightly ciliate. Each leaf has a short petiole or it is nearly sessile; there is a membranous sheath (ochrea) that wraps around the stem at the base of each petiole. This sheath may have a few longitudinal veins and there are deciduous bristles along its upper rim that may exceed 1 mm. in length. The upper surface of a leaf often has a black smudge that is oval or triangular-shaped; this smudge may be dark and conspicuous or faint and barely perceptible. Each upper stem terminates in 1 or 2 spike-like racemes of flowers; there are often shorter racemes that develop from the axils of the upper leaves on peduncles. Each raceme is about ½–1½" long, more or less erect, and oblongoid in shape from the crowded whorls of small flowers. The sepals of the flowers may be pink, red, greenish white, or purple, even on the same raceme; usually pink flowers are the most common. Each flower is about 1/8" long and shy to open; it consists of 5 sepals, 6 stamens (usually), a style that is divided into 2-3 parts toward the middle, and no petals. The sepals are not glandular-punctate, and the stamens are not exerted beyond the sepals. The blooming period can occur from late spring to early fall; a colony of plants will typically bloom for 1-2 months during the summer. There is no noticeable floral scent. Each flower is replaced by a seed that ovoid, flattened or slightly 3-angled, black, and shiny. The shallow root system doesn't produce rhizomes. This plant often forms colonies, particularly in disturbed wetland areas, or it may occur in drier areas as scattered plants. Reproduction is by seed only.