Rumex britannica (Great Water Dock)

Plant Info
Also known as:
Genus:Rumex
Family:Polygonaceae (Buckwheat)
Life cycle:perennial
Origin:native
Habitat:part shade, sun; moist to wet; fens, seeps, shores, stream banks, marshes, wet ditches, swales
Bloom season:June - July
Plant height:3 to 6 feet
Wetland Indicator Status:GP: OBL MW: OBL NCNE: OBL
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 3-petals Flower shape: indistinct Cluster type: panicle Cluster type: whorled

[photo of whorled flower clusters] Branching clusters at the top of the plant, each branch with numerous whorls of 15 to 25 slender-stalked flowers, usually crowded towards the branch tips and more widely separated below. Flowers are up to about 1/4 inch long (4 to 7 mm), green to pinkish, 3-sided with 2 series of tepals (petals and similar sepals) and the outer tepals much smaller than the inner. The 3 inner tepals, also called valves, are egg-shaped to nearly round, distinctly veined across the surface, the edges flat to slightly wavy and smooth to slightly jagged. At the base of each inner tepal is a projection called a grain, about half as long (or slightly more) as the tepal, lance-oblong typically tapering to a pointed tip, with the grains of all 3 tepals about the same size. Tepals are spreading at flowering time, revealing stamens and styles, and close up after pollination. Flower stalks are very slender and smooth, about twice as long as the inner tepals at flowering time, with an obscure joint in the lower third.

Leaves and stems: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of basal leaves] Leaves are both basal and alternate, hairless, toothless to shallowly scalloped around the edge, and have lateral veins nearly perpendicular to the midvein. Basal leaves are lance-oblong, the blade 1 to 2+ feet long and to 3 inches wide, flat to slightly wavy, blunt to pointed at the tip, wedge-shaped to straight across at the base, on a stalk about as long as the blade. New leaves are erect, rolled under along the edge and unfurl like a scroll, and are often tinged red to a bronzy orange color.

[photo of stem leaf] Leaves become smaller, more tapering at both ends, more sharply pointed at the tip, shorter stalked, and often more crinkled around the edge as they ascend the stem. At the base of the leaf stalk is a brownish papery sheath (ocrea) that surrounds the stem and mostly disintegrates with maturity. Stems are stout, erect, mostly unbranched except in the flower clusters, ribbed and hairless.

Fruit: Fruit type: capsule/pod Fruit type: seed without plume

[photo of mature fruits] A flower produces a single seed, wrapped in the persistent tepals, which form a capsule-like structure and dry to brown.

[photo of seed] Seeds are 3-sided, elliptic to egg-shaped with a short taper at the tip, reddish brown, and 3 to 4.5 mm long.

Notes:

Great Water Dock, formerly known as Rumex orbiculatus, is a native wetland species found throughout most of Minnesota. There are at least 11 similar Rumex species in the state, 5 of which are native. Some of the distinguishing characteristics are whether the leaves are crinkly-wavy or relatively flat, the shape of the inner tepals at maturity, size and shape of the grains, whether the grains on all 3 inner tepals are about the same size, sometimes the length of the flower stalk or where the stalk is jointed or the vein pattern on the leaves. Great Water Dock is the tallest of the native docks in Minnesota, with large, mostly flat basal leaves, tepals up to 7 mm long that are egg-shaped to nearly round and only slightly ragged around the edge, all 3 grains about the same, grains half as long or so as the tepal and typically tapering to a pointed tip, the flower stalk obscurely jointed in the lower third, and lateral leaf veins nearly perpendicular to the midvein.

Compare to Curly Dock (Rumex crispus), a common weed of disturbed soils, roadsides and waste areas, with leaves that are all very crinkly-wavy around the edge, grains that are half or less as long as the tepal, rounded at the tip, and usually with 3 grains (rarely 1 or 2) unequal in size. Dooryard Dock (Rumex longifolius), a less common weed of disturbed soils, has broader and more crinkled leaves than Great Water Dock, larger, heart-shaped tepals and essentially no grains at all, just a very slight swelling at the base of the midvein. Bitter Dock (Rumex obtusifolius), has broader basal leaves with heart-shaped bases and tepals have large teeth around the edge.

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More photos

Photos by K. Chayka taken at Pine Bend Bluffs SNA, Dakota County, and Battle Creek Park, Ramsey County. Photos courtesy Peter M. Dziuk taken in Le Sueur, Pine and Winona counties.

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