1. Pastinaca sativa L. (parsnip, wild parsnip)

Pl. 210 g, h; Map 873

Plants biennial. Stems 35–150(–200) cm long, erect, relatively stout, usually strongly ridged, glabrous or sparsely to moderately short-hairy. Leaves alternate and often also basal (a few basal leaves usually present at flowering), glabrous or the undersurface short-hairy, short- to long-petiolate, the sheathing bases of lower leaves not or only slightly inflated, those of the middle and upper leaves sometimes somewhat more inflated. Blades of the basal and main leaves 5–55 cm long (uppermost leaves usually highly reduced and nearly bladeless), oblong-elliptic to ovate in outline, pinnately 1 or 2 times compound, the leaflets 10–200 mm long, lanceolate or ovate to nearly circular, narrowed to less commonly shallowly cordate at the base, toothed (often coarsely so) and often shallowly to deeply lobed, rounded or narrowed to a blunt point at the tip. Inflorescences terminal and axillary, compound umbels, these sometimes appearing in loose clusters of 3 or 5, short- to long-stalked, the stalks glabrous or minutely hairy. Involucre absent. Rays 5 to numerous, 2–10 cm long, unequal in length, glabrous or minutely hairy. Involucel absent. Flowers 8 to numerous in each umbellet, the stalks 2–10 mm long (the central flower sometimes sessile), elongated slightly at fruiting, glabrous or minutely hairy. Sepals absent. Petals ovate, narrowed or tapered to a short, slender tip, yellow, occasionally tinged with red. Ovaries glabrous. Fruits 5–7 mm long, oblong-elliptic or broadly elliptic to slightly oblong-obovate in outline, flattened dorsally, glabrous, tan to light greenish brown with usually prominent reddish brown oil tubes between the ribs, each mericarp with the intermediate and dorsal ribs slender and nervelike, hardly raised from the surface, the lateral ribs with thin, broad wings. 2n=22. May–October.

Introduced, scattered to common nearly throughout the state, but apparently still absent from the Mississippi Lowlands Division and adjacent Ozarks (native of Europe; introduced widely in the U.S. and Canada). Disturbed portions of upland prairies and banks of streams; also pastures, fallow fields, old fields, fencerows, roadsides, railroads, and open, disturbed areas.

Although the tuberous roots of the cultivated form of parsnip are edible, the aboveground portions of both cultivated and weedy races have been reported to contain furanocoumarins and related compounds similar to those found in Heracleum and may cause phototoxic dermatitis in some individuals.