PNW 446 • March 1993 Red Sorrel Rumex Acetosella L. J.P. Fitzsimmons and L.C. Burrill

Red sorrel (Rumex acetosella) also is known as sheep, horse, field, mountain, and cow sorrel or sour dock. This European DATE. weed grows throughout the Pacific Northwest under vari- ous soil and climate conditions. OF While it apparently thrives on acid soils with low fertility, it is Figure 1.—The typical color of red adapted to other soil conditions. sorrel simplifies identification. Figure 2.—The papery sheeth on the Competition from other plants with one or two conspicuousOUT stem at the left and the basal lobes on on better soils reduces its basal lobes. The slender leaf the leaf at the right help distinguish abundance. It occurs in lawns, stalks haveIS a papery sheath red sorrel. fields, gardens, along road- where they attach to the stem. depends on several unknown sides, and in burn areas. Red Both the stems and leaves are factors, and it appears that sorrel is especially unwelcome acrid tasting, resembling Rumex with a dangerous level in fields of clover grown for rhubarb, which also is in the of oxalate content are rare. seed because the red sorrel buckwheat family. Male and seeds are difficult, if not female flowers are produced impossible, for commercial on differentinformation: plants, which bear CONTROL seed cleaners to separate from the flowers in branched MECHANICAL. Control red clover seed. clusters at the top. Yellow- sorrel in pastures or perennial orange flowers produce large crops by shifting to annual Red sorrel is not classified as quantities of pollen. Red- crops that require or accom- noxious in the Pacific North- orange female flowers blos- modate tillage. west. There is evidence thatcurrentsom from May to September the seeds PUBLICATIONlast long enough in producing small, three-angle A 4-year rotation to include a the soil to provide a source for fruits enclosed in reddish, clean-cultivated crop, fol- new infestations every time persistent flower parts. The lowed by a grain crop, cover the soil is disturbed. triangular seeds are a polished crop or clover, and returning most mahogany color. to a pasture or perennial crop helps reduce infestations. THISIDENTIFICATION Effectiveness of control Red sorrel is a rhizomatous, TOXICITY depends on the thoroughness creepingFor perennial that repro- Red sorrel is considered safe and persistence of cultivation. duces by seed and by under- for human consumption as a Another method is to repeat ground stems. Above-ground fresh herb or when boiled, but stems oftenhttp://extension.oregonstate.edu/catalog are less than 12 there is potential for poisoning inches tall but grow up to 2 of livestock. Species of Rumex Jim P. Fitzsimmons, graduate feet tall with few lateral owe their toxicity to soluble student, crop and soil sciences; and branches. Lower leaves are oxalates. The degree to which Larry C. Burrill, Extension weed somewhat arrowhead shaped oxalates accumulate in plants specialist, Oregon State University.

A Pacific Northwest Extension Publication • Oregon • Idaho • Washington cultivation during dry control red sorrel. Selective weather, which gradually control in broadleaf crops or USE PESTICIDES SAFELY! weakens and destroys roots. pasture crops with legumes is more difficult. Repeated • Wear protective clothing Cultivation must be at short applications may be necessary and safety devices as intervals to deplete root re- in any situation. recommended on the serves, but plants must be label. Bathe or shower after allowed time to produce 2 or 3 Herbicide registrations change each use. inches of green tissue between frequently; therefore, this • Read the pesticide label— cultivations for maximum publication does not contain even if you’ve used the depletion of reserves. Liming specific herbicide use instruc- pesticide before. Follow and nitrogen fertilization to tions. Registered uses are closely the instructions on the label (and any other increase soil pH and enhance summarized each year in the Pacific Northwest Weed Control directions you have). other plant growth where • Be cautious when you Handbook. practical may reduce red sorrel apply pesticides.DATE. Know infestation. Remove small your legal responsibility patches of red sorrel from In addition, detailed instruc- as a pesticide applicator. gardens and flower beds by tions for herbicide use are YouOF may be liable for injury aggressively digging with a provided on herbicide con- or damage resulting from shovel or potato fork to expose tainer labels and in other pesticide use. and remove the rhizomes. literature provided by herbi- cide manufacturers. CHEMICAL. In non-crop OUT areas or in grass crops, several herbicides can selectively IS

information:

PUBLICATIONcurrent most THIS Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the Oregon State University Extension Service, O.E. Smith, director; Washington State University Cooperative Extension, Larry G. James, interim director; the University For of Idaho Cooperative Extension System, LeRoy D. Luft, director; and the U.S. Depart- ment of Agriculture cooperating.

http://extension.oregonstate.edu/catalogThe three participating Extension Services offer educational programs, activities, and materials—without regard to race, color, national origin, sex, age, or disability—as required by Title VI of the Civil Rights Act of 1964, Title IX of the Education Amendments of 1972, and Section 504 of the Rehabilitation Act of 1973. The Oregon State University Extension Service, Washington State University Cooperative Extension, and the University of Idaho Cooperative Extension System are Equal Opportunity Employers. 50/0/50