What Is Wood Sorrel?
By Patricia H. Reed
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Whether digging in your garden, mowing the lawn or taking a walk in the park, you've likely come across wood sorrel. Whether you yank it out with a curse, exclaim at its beauty or pucker your lips at its tart, lemony flavor depends on the species you encounter -- though some prompt all three responses. Several of species of these plants, which feature cloverlike clusters of dainty heart-shaped leaves, are widespread across the United States, while others confine themselves to warmer climates or are treated as houseplants.
Oxalidaceae
At its most basic level, wood sorrel (Oxalis spp.) is a large genus of annual and perennial plants in the Oxalidaceae family. The names of the family and genus are derived from the Greek word for sour, "oxys." Plants in this family contain varying levels of oxalic acid in their foliage, which gives them a tart flavor, though the plants can be toxic if consumed in large quantities.
Weedy Wood Sorrels
Yellow wood sorrel (O. stricta) and creeping wood sorrel (O. corniculata) are the most common wood sorrels found in yards and gardens and are widely considered weeds. The plants are perennial down to U.S. Department of Agriculture plant hardiness zones 3 and 4 respectively, and they plague gardeners across the United States with their ability to spread and regenerate. Yellow wood sorrel has smooth, bright green leaves, grows about 8 inches tall and spreads through underground rhizomes. Creeping sorrel is lower to the ground, only about 4 inches tall with purplish-green, slightly hairy leaves and spreads through stolons, which move along the top of the ground putting down new roots. Both types have five-petaled yellow flowers. Control of both is primarily by hand digging and repeat pulling, though a long taproot makes this difficult. Glyphosate and broadleaf herbicides labeled for use on oxalis are effective, though you might need to apply them several times to eliminate the plants.
Ornamental Wood Sorrels
Numerous wood sorrel species are considered wildflowers, featuring the same heart-shaped leaves as weedy varieties. They vary in size and color and offer attractive blooms in a range of colors and sizes. These plants may be used as houseplants, in borders, or as ground covers. Redwood sorrel (O. oregano) is a native species perennial in USDA zones 7 through 9 that grows up to 12 inches tall with white, pink or pink-purple flowers. Windowbox wood sorrel (O. rubra), perennial to zone 9 and used as a houseplant or annual elsewhere, grows from a bulb, has showy pink flowers with darker veins and grows 6 to 12 inches tall. Purple wood sorrel (O. purpurpea) grows 4 to 6 inches tall with purple flowers. The "Alba" cultivar has white blossoms, while "Garnet" features purple flowers and foliage. They are hardy in zones 9 and 10.
Wood Sorrels to Watch For
Though not officially considered invasive species, some ornamental wood sorrel species have escaped cultivation in areas with mild climates to make themselves at home in waste areas -- roadsides, woodlands, and other areas of abandoned soil. Keep any plantings in check by deadheading flowers and digging up and disposing of plants that spread beyond their bounds, or control them before they set seed with a broadleaf herbicide specified for use on oxalis. Bermuda buttercup (O. pes-caprae) is the one plant in the family, though not commonly called wood sorrel, that should be avoided. Bermuda buttercup features large bright yellow flowers an is hardy in zones 9 and 10. It spreads via bulb and is difficult to eliminate once established.
Fine Gardening: Genus Oxalis
Oregon State UniversityNorth Willamette Research & Extension Center: Oxalis Corniculata, Oxalis Stricta
University of California Integrated Pest Management: Creeping Woodsorrel and Bermuda Buttercup
Wyman's Gardening Encyclopedia; Donald Wyman
Sunset: Oxalis Oregana
Bulbs: How to Select and Grow More Than 400 Summer-Hardy and Tender Bulbs; Barbara W. Ellis
Missouri Botanical Garden: Oxalis Purpurpea
Plant of the Week: Oxalis Rubra, Windowbox Wood Sorrel
Weeds of California and Other Western States, Volume 1; Joseph M. DiTomaso
California Invasive Plant Council: Oxalis pes-caprae (Bermuda Buttercup, Buttercup Oxalis, Yellow Oxalis)
University of California Extension Under the Solano Sun: Sour Grass is a Pain in the...!
Patricia Hamilton Reed has written professionally since 1987. Reed was editor of the "Grand Ledge Independent" weekly newspaper and a Capitol Hill reporter for the national newsletter "Corporate & Foundation Grants Alert." She has a Bachelor of Arts in journalism from Michigan State University, is an avid gardener and volunteers at her local botanical garden.
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