Wild Parsnip (Pastinaca sativa) Identification and Control in Residential Landscapes Michael Caron, Taun Beddes, and Corey Ransom
Description
Summary
Wild parsnip (Pastinaca sativa) is an herbaceous, biennial, or short-lived perennial weed in North America native to Eurasia. The species produces furanocoumarins in the sap, stems, and leaves that cause severe burns (phytophotodermatitis) and blisters when the sap is on the skin surface and exposed to sunlight or UV light from other sources. Concentrations of furanocoumarins can increase in plants if insects feed on it or plants are cut back and allowed to regrow.
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After exposure, skin is often discolored and more sensitive to the sun for up to two years. Cultivated parsnips are closely related and have far fewer furanocoumarins than wild forms. The quantity of furanocoumarins in wild populations also varies widely, depending on the population.
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Wild parsnip is a weed that can potentially cause serious injury to gardeners. It thrives in sunny locations in many landscapes and wildland habitats. It grows a rosette of leaves in the first year and a tall flower stalk in Years 2 or 3, after which the plant dies. It primarily propagates by seed, and seeds are dispersed by wind, rain, animals, or other disturbance to the dry flowers. Non-herbicide control options include tilling 2 inches deep or mowing before flowering. Many herbicides effectively control wild parsnip, including those containing 2,4-D.
Leaves are pinnately compound with five to 15 toothy leaflets. Yellow flowers are produced late spring through midsummer and are small, fivepetaled, numerous, and on flat-topped umbels 2–6 inches wide. The yellow flowers and pinnately compound leaves of more than five toothed leaflets distinguish it from other parsnip species (Figure 1). The taproot is slender and light-colored, penetrating 6–12 inches into the soil. Plants grow to 3–6 feet tall and wide by late summer. It spreads by seed, and humans unknowingly spread it when mowing, removing, or disturbing the plant after seeds have formed.
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