Rumex verticillatus L.

Swamp Dock


CC = 7
CW = -5
MOC = 39

© SRTurner

Family - Polygonaceae

Habit - Perennial, monoecious forb with a stout, vertical rootstock, sometimes rooting at the lower nodes.

Stem - Ascending to erect, to 1.0 m, mostly solitary, sometimes from a spreading base, usually few-to several-branched below the inflorescence, glabrous or nearly so.

Rumex_verticillatus_stem.jpg Stem and node.

© SRTurner

Leaves - Alternate, basal rosette usually absent at flowering, simple. Ocreae white or translucent and membranous to more or less papery, becoming shredded into fibers with age. Leaf blades 5-30 cm long, 1-5 cm wide, usually relatively thin, not or only slightly leathery, narrowly lanceolate to lanceolate, those of the uppermost leaves sometimes nearly linear, unlobed, the margins entire, flat or somewhat crisped or undulate, narrowly angled at the base, angled or tapered to a usually sharply pointed tip, the surfaces glabrous.

Rumex_verticillatus_leaf1.jpg Leaf adaxial.

© SRTurner

Rumex_verticillatus_leaf2.jpg Leaf abaxial.

© SRTurner

Rumex_verticillatus_leaf2a.jpg Leaf abaxial surface.

© SRTurner

Inflorescences - Terminal and axillary, the terminal ones usually occupying the upper 1/3-1/2 of the plant, narrowly paniculate, the main axis often somewhat zigzag, mostly relatively open and interrupted, at least below the midpoint. Flowers 10-15 per whorled fascicle, the stalks 10-17 mm long, 2-5 times as long as the fruiting perianth, mostly strongly arched downward or nodding at maturity, jointed toward the base. Staminate flowers produced toward the inflorescence tips but generally not apparent at fruiting.

Rumex_verticillatus_inflorescence1.jpg Inflorescence.

© SRTurner

Rumex_verticillatus_inflorescence2.jpg Inflorescence whorls.

© SRTurner

Flowers - Pistillate flowers with the inner whorl of tepals becoming enlarged to 3.5-5.0 mm long and 2.5-4.0 mm wide at fruiting, moderately to broadly winged, ovate to ovate-triangular, truncate or broadly rounded at the base, narrowly rounded or sharply pointed at the tip, the margins entire, the surfaces with a prominent network of nerves; tubercles 3, all of similar size or 1 of them slightly larger than the others, covering up to 1/2 of the width of the tepals (including the wings), glabrous, sometimes minutely pitted, pebbled, or slightly cross-wrinkled; the outer whorl spreading to somewhat reflexed at fruiting.

Fruits - Achenes 2.3-3.1 mm long, 1.6-2.2 mm wide, brown or dark brown.

Rumex_verticillatus_fruits.jpg Tepals and tubercles at fruiting stage.

© SRTurner

Flowering - April - June.

Habitat - Swamps, sloughs, oxbows, bottomland forests; often emergent aquatics.

Origin - Native to the U.S.

Lookalikes - Other species of Rumex.

Other info. - Species of Rumex are often ignored, as they tend to be coarse, weedy looking, and somewhat difficult to identify to species. The flowers have no showy parts and are virtually invisible at normal viewing distances. Some species can be pernicious pests of crop fields. Swamp dock, however, is a relatively conservative species usually found in undisturbed habitats. It is one of the easiest species of Rumex to identify to species (when in the fruiting stage) due to its whorls of long-stalked fruits, appearing a bit like a series of tiny grass skirts arranged along the inflorescence axis. The fruiting tepals have smooth, entire margins, and there are usually three tubercles per fruit. The species is scattered throughout Missouri, and is probably a little more common toward the eastern side of the state. Its range beyond Missouri extends southward to the Gulf Coast and northeastward into New England.

Photographs taken at Otter Slough Conservation Area, Stoddard County, MO, 5-14-2016, and at Marais Temps Clair Conservation Area, St. Charles County, MO, 5-31-2021 (SRTurner).