Curly Dock

Curly dock plants blooming on a field margin north of Jefferson City
Scientific Name
Rumex crispus
Polygonaceae (smartweeds, knotweeds, buckwheats)

Curly dock is a perennial plant with a thickened taproot that begins as a basal rosette of lance-shaped leaves with wavy margins and distinct leaf stems. As the smooth, ribbed stem grows taller, it bears alternate leaves that are progressively smaller and narrower up the stalk. The leaves have a tan or reddish-brown, membrane-like sheath that encircles the stem (this sheath, called an ocrea, is distinctive of the smartweed, knotweed, or buckwheat family). The leaves are herbaceous to somewhat leathery, with untoothed, unlobed, but crisped and wavy margins.

The flower clusters are terminal, many-branched, narrow panicles whose branches are strongly ascending; the clusters usually constitute the upper half of the plant. The flowers are many, about ⅛ inch long, consisting of yellowish-green sepals that redden as they mature. Each flower’s stalk nods or droops. The flowers are not fragrant. Blooms April–June.

Fruits are dry, about ¼ inch long, with 3 rather broad wings (valves); the single, rather large seed within each fruit is 3-angled. The clusters of mature fruits, along with the entire top of the plant, turn dark brown when mature and are easily seen along roadsides.

Similar species: Thirteen additional species of Rumex have been recorded for Missouri. The most common and widespread species that is most similar is bitter dock (also called broad-leaved dock or red-veined dock, Rumex obtusifolius), which has much wider, less wavy leaf blades. It, too, is a Eurasian native introduced to our continent, and it also occurs nearly statewide and in similar habitats.

Because it is so widespread and well-known, curly dock and its relatives have been the namesake for several other plants that have similar leaves. Prairie dock (Silphium terebinthinaceum), for instance, is in the sunflower family with sunflower-like flowers, but its whorls of broad, leathery leaves look very similar to this Rumex dock from the Old World. Pale smartweed (Persicaria lapathifolia) is sometimes called “dock-leaved smartweed” for its leaf shape, too.

Other Common Names
Sour Dock
Yellow Dock

Height: usually 16–40 inches.

Where To Find

Common statewide.

Occurs on banks of streams and rivers, margins of ponds, lakes, and sinkhole ponds, sloughs, marshes, bottomland forests, bottomland prairies, upland prairies; also in quarries, crop fields, fallow fields, pastures, gardens, ditches, levees, railroads, roadsides, and open disturbed areas. It occasionally grows as an emergent aquatic plant.

This species, native to Europe and Asia, has been introduced nearly worldwide.

Nonnative perennial forb; introduced to our continent from Eurasia. Spreads by seeds. Usually considered a weed of pastures, hay fields, and crop fields.

Used as a wild edible green. Some people, however, may develop skin irritation on contact with the plant.

In some people, contact with the plant can cause dermatitis.

Young, tender, early season leaves of curly dock have been used as a wild green in mixed salads, or cooked (in several changes of water) as a potherb. The seeds have been ground into a flour and eaten, similar to buckwheat. Because of the high oxalic acid content in the leaves, it is best not to overindulge. Oxalic acid is also common in several other plants such as spinach, wood-sorrels, lamb’s quarters, parsley, sorrel, and rhubarb. (Sorrel and rhubarb are in the same family as curly dock.)

Oxalic acid, synthesized in a chemical process, is used as a bleaching agent, as in tooth-whitening powders, wood bleach, and in products such as Bar Keepers Friend.

If you are wanting to eat curly dock, study preparation methods and possible toxicity. Oxalic acid makes the plant taste tart. Too much oxalic acid can irritate the urinary tract and increase the risk of developing kidney stones. If you have kidney problems, you should probably avoid eating it. Also, older leaves are high in tannins, which make them taste bitter.

The roots have been sold for their medicinal value under the name yellow dock.

Both Iowa and Arkansas, our neighbors to our north and south, have officially classified curly dock as a noxious weed. Among midwestern states, Iowa and Michigan have listed it as invasive.

Curly dock is wind-pollinated, and it can contribute to people’s seasonal allergies. Because it usually blooms about the same time that many grasses are also releasing large amounts of pollen into the air, it usually isn’t recognized as a main cause of hay fever.

Some species of docks store tannins in their enlarged rootstocks and were once used in the tanning of animal hides for leather.

Apparently, few mammals eat curly dock on account of its sour, bitter, toxic foliage. Like us, however, they may find the young, early spring leaves somewhat palatable. Rodents reportedly eat the fruits, as do a variety of birds.

Because curly dock is cross-pollinated by wind, its flowers attract few insect pollinators.

A wide variety of insects eat curly dock. Many of these are generalists that eat many kinds of plants, but several specialize in eating curly dock and its close relatives. Here are some of the insects whose favorite or only foods are species of Rumex:

  • the dock aphid (Aphis rumicis), a black, wide-bodied aphid that specializes in sucking the juices of docks and sometimes rhubarb
  • the rapid plant bug (Adelphocoris rapidus), a brownish plant bug trimmed with yellow or orange; it commonly sucks the juices of dock plants
  • the green dock beetle (Gastrophysa cyanea), a small, shiny, oval leaf beetle that is black with a green or blue iridescent sheen; the back is punctate (dotted) with tiny indentations; both adults and larvae chew the leaves
  • the rhubarb weevil (Lixus concavus), a long-bodied, long-nosed beetle with a bright yellow or orangish, dusty-looking bloom on its body; its young develop within the stems of dock and its relatives, including rhubarb
  • Pegomya bicolor, a fly whose larvae are leaf miners, creating big, tan, dead blotches on the leaves of docks and other members of the family as they eat the inner layer of tissues of leaves; the adult flies have a grayish thorax and orangish abdomen
  • the dock seed midge (Contarinia rumicis) is a gall-forming midge whose larvae develop in the flowers and fruits of dock plants, causing the plant to create reddish, warty galls in response
  • the dock sawfly or dock false-worm (Ametastegia glabrata), a nonnative wasplike insect whose caterpillar larvae eat the leaves of members of the smartweed family
  • the American copper (Lycaena phlaeas americana), one of the world’s most widespread butterfly species, uses curly dock, sheep sorrel, and other members of the smartweed family as caterpillar food plants.
  • the American bird’s-wing (Dypterygia rozmani), a brown noctuid moth whose unusual wing pattern looks like a bird in flight; its caterpillars feed on docks and smartweeds
  • the dock rustic (Resapamea passer), a tan noctuid (dart or cutworm) moth whose larvae bore into the roots of dock plants
  • the pink-barred pseudeustrotia (Pseudeustrotia carneola), a tan noctuid moth marked with a big, pale pink X when it’s at rest; its caterpillars feed on dock among other plants
  • the ruby tiger moth (Phragmatobia fulginosa), whose larvae use dock as a principal food plant; adults have brown forewings, but the bodies are bright orange-red with rows of black spots.

Globally, there are about 200 species in genus Rumex. A close relative is sheep sorrel (R. acetosella), a common pasture weed with red stems and flowers that can cover large patches of ground. Others in the genus include common sorrel and French sorrel (R. acetosa and R. scutatus), which are cultivated as sour-tasting additions to salads. The genus Rheum is closely related to Rumex; it is the genus that includes rhubarb.

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About Wildflowers, Grasses and Other Nonwoody Plants in Missouri
A very simple way of thinking about the green world is to divide the vascular plants into two groups: woody and nonwoody (or herbaceous). But this is an artificial division; many plant families include some species that are woody and some that are not. The diversity of nonwoody vascular plants is staggering! Think of all the ferns, grasses, sedges, lilies, peas, sunflowers, nightshades, milkweeds, mustards, mints, and mallows — weeds and wildflowers — and many more!