IUCN threat status:

Not evaluated

Comprehensive Description

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Description

This perennial plant is emergent-aquatic and 1-3' tall, consisting of a rosette of basal leaves and one or more flowering stalks. Mature leaves are 4-14" long and 3-10" across; they are sagittate or hastate in shape and smooth along their margins. The leaves have conspicuous primary veins and smaller lateral veins; their venation is palmate-parallel overall. There is considerable variability in the width of the leaves and the length of their basal lobes across different populations. However, the basal lobes are at least as long as the main bodies (or terminal lobes) of the leaves. The upper leaf surface is pale green, medium green, or yellowish green, while the lower leaf surface is pale green or yellowish green. Both sides of the leaves are glabrous. The ascending petioles of the leaves are 6-18" long and rather stout; they broaden toward the base and become sheath-like. Each petiole is flat on one side, otherwise it is rounded (convex). The flowering stalks (including both peduncles & floral rachises) are about as tall as the leaves or slightly taller and ascending to erect; they are angular or terete. These stalks are either branched or unbranched; sometimes 1-2 lateral branches are produced below the rachis of the terminal stalk. Each branch of the inflorescence terminates in a raceme of whorled flowers; there are 2-3 flowers per whorl. The terminal raceme typically has 3-9 whorls of flowers, while the lateral racemes (if present) have 2-5 whorls of flowers. The whorls of flowers are spaced about 1-2" apart along each raceme. Most plants are monoecious; the male (staminate) flowers are located above the female (pistillate) flowers in each raceme. Occasionally, dioecious plants occur, and sometimes perfect flowers are produced. Underneath each whorl of flowers, there are 2-3 floral bracts that join together at the base. These floral bracts are up to ½" long, linear-lanceolate to lanceolate in shape, green, and glabrous. Each flower is about 1" across, consisting of 3 white rounded petals and 3 green ovate sepals. The male flowers have numerous stamens that are yellow, while the female flowers have clustered carpels that are green and form a small bur-like mass. The filaments of the stamens are hairless. The spreading to ascending pedicels of the flowers are up to 1" long; they are green and glabrous. The blooming period occurs from mid-summer to early fall, lasting about 1-3 months for a colony of plants. Afterwards, the female flowers are replaced by bur-like fruits that are up to ¾" across at maturity, changing in color from green to dark brown as they mature. These fruits are are globoid to subgloboid (globoid, but slightly flattened) in shape, consisting of a dense cluster of achenes. Because of the lateral beaks of the achenes, these bur-like fruits appear more streaked than prickly. The sepals of these fruits are widely spreading to recurved; they slowly wither away. Individual achenes are 2.0-3.0 mm. long, 1.5-2.0 across, and flattened-obovoid or flattened-obdeltoid in shape; some of their margins are membranous and winged. Each achene has a more or less straight beak about 1.0-1.5 mm. in length that projects laterally from its upper side. The root system consists of a tuft of coarse fibrous roots and long spreading stolons, from which starchy tubers are occasionally produced. This plant reproduces by reseeding itself or by forming clonal plants from the tuberous stolons. Colonies of plants sometimes develop at favorable sites.

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© John Hilty

Source: Illinois Wildflowers

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