Description: This native perennial plant is
about 2–3' tall and sparingly branched. The central stem is more or less
erect (for terrestrial plants), swelling somewhat at the nodes where the
leaf-sheaths wrap around the stem. These nodes can be brownish and hairy, but
are never bristly at the edges. The alternate leaves are up to 8" long and 3"
across, and have short petioles. They are usually lanceolate or
ovate-lanceolate. Their margins are smooth, although they may curl up and down
or twist about. The surface of the leaves (upper and lower) can be either
hairless, or have appressed silvery hairs, depending on the local ecotype. The
midvein on the underside of each leaf is quite prominent. Their are 1 or 2
terminal racemes of flowers at the apex of the central stem. The flowering
stalks are quite hairy and often brownish in appearance. The cylindrical
racemes are about 2-3" long and densely crowded with flowers. Each flower is
about 1/6" across, consisting of 5 petal-like sepals, 5 stamens, and a divided
white stigma. The sepals of these flowers are rosy pink or scarlet, and rather
showy. The blooming period can occur from mid-summer to early fall, and lasts
about 1-2 months for a colony of plants. There is no noticeable floral scent.
The black seeds are oval or orbicular in shape, with a shiny surface that may
be slightly granular. The root system produces long rhizomes, which enable this
plant to form sizable colonies.
Cultivation: The preference is wet soil that is
prone to flooding, and full sun. This plant will grow in shallow water,
assuming an aquatic habit, and can also grow in soil that is steadily moist. It
does not tolerate drought. The foliage is bothered by few pests and disease,
and is usually attractive, unless attacked by Papilio japonica (Japanese
Beetles). Scarlet Smartweed can spread aggressively to form large colonies in
wet areas.
Range & Habitat:
Scarlet Smartweed occurs occasionally in most counties of Illinois; it is less
common or absent in southern Illinois, preferring the poorly drained glaciated
areas of the state. Habitats include moist meadows or prairies in areas prone
to flooding; marshes, swamps, and borders of ponds and lakes, including areas
with shallow water; and ditches along roads and railroads. This is primarily a
wetland plant
that is found in
the sloughs of prairies, sometimes growing beside Iris virginica shrevei
(Blue Flag Iris).
Faunal
Associations: The flowers attract many kinds of insects, especially
flies, wasps, and small bees. Other flower visitors include small butterflies,
skippers, and beetles. These insects seek nectar primarily. The caterpillars of
the moths Lithacodia synochitis (Black-Dotted Lithacodia) and
Lithacodia carneola (Pink-Barred Lithacodia) feed on the foliage, while
the caterpillars of the butterfly Strymon melinus (Gray Hairstreak) eats
the flowers and buds. The seeds of smartweeds are a popular source of food to
many kinds of birds, especially those that inhabit wetlands (see
Bird Table; many wetland birds
have not been listed). Mammalian herbivores usually don't consume smartweeds to
any great extent because of the peppery/bitter taste of the leaves, although
deer sometimes chomp off the tender tops of plants.
Photographic Location: The photographs were taken of
plants growing in a flood-prone area of a moist remnant prairie, which was
located between a road and an abandoned railroad in Champaign County,
Illinois.
Comments: Scarlet
Smartweed is my favorite smartweed because of its beauty. The leaves often
shimmer in the sunlight because of their silky hairs, while the individual
flowers are large-sized for a smartweed and quite colorful. Recently, the
smartweeds have been separated from the knotweeds by taxonomists and
re-assigned back to the Persicaria genus. Formerly, Scarlet Smartweed
has been assigned such scientific names as Polygonum coccineum,
Polygonum amphibium var. emersum, and Polygonum muhlenbergii.
Sometimes Scarlet Smartweed is lumped together with Polygonum amphibium
(Water Smartweed), but these are quite different species, the latter having
flowering racemes that are shorter and cone-shaped, rather than cylindrical.
Scarlet Smartweed can be distinguished from other smartweeds by its large size,
erect racemes of colorful flowers, and the presence of conspicuous hairs on the
flowering stalks and leaf-sheaths.