1. Perilla frutescens (L.) Britton (beefsteak plant, wild basil, summer coleus, rattlesnake weed)

Pl. 438 j, k; Map 1977

Plants annual, with taproots. Stems 20–80(–100) cm long, erect or ascending, bluntly to sharply 4-angled, branched, sparsely to moderately pubescent with loosely downward-curved, multicellular hairs, more densely so toward the tip and around the nodes, often nearly glabrous toward the base, sometimes strongly purplish-tinged. Leaves opposite, mostly long-petiolate, the petioles unwinged, with an unpleasant, pungent odor when bruised or crushed. Leaf blades 3–15 cm long, sometimes entirely or mostly dark brownish purple, oblong-ovate to broadly ovate or occasionally broadly elliptic, unlobed, the margins coarsely toothed, rarely with slender irregular lobes (incised), broadly angled to angled or short-tapered at the base, angled or tapered to a sharply pointed tip, the surfaces glabrous or more commonly sparsely short-hairy, mostly along the veins, the undersurface also with conspicuous sessile glands. Inflorescences terminal and axillary, of relatively dense, slender, usually elongate spikelike racemes, the flowers 2 per node (1 on each side of the axis), these short-stalked. Bracts 3–6 mm long, not extending past the calyces, elliptic to ovate, sharply pointed but not spinescent; bractlets absent. Calyces 2–3 mm long at flowering, slightly zygomorphic, lacking a lateral projection, symmetric at the base at flowering, more or less bell-shaped, the tube 10-nerved, the nerves obscured by usually dense, spreading, multicellular hairs on the outer surface, sparsely hairy in the mouth, the lips slightly shorter than to slightly longer than the tube, the upper lip curved slightly upward, with 3 triangular lobes, the lower lip slightly curved upward, with 2 deeper, narrowly triangular lobes, the lobes all tapered to sharply pointed, but not spinescent tips, usually with relatively dense, sessile glands and sometimes with a few spreading, nonglandular hairs toward the base on the outer surface, becoming enlarged to 8–12 mm, papery, and swollen or pouched basally on the lower side at fruiting. Corollas 2.5–4.0 mm long, nearly actinomorphic, not 2-lipped, white to lavender or light purple, lacking darker purple spots, the outer surface glabrous or more commonly sparsely hairy, more or less bell-shaped, the tube hairy in the throat, the 5 lobes very short, all similar or nearly so (the lowermost lobe sometimes slightly larger and/or slightly more spreading), broadly rounded to bluntly pointed, somewhat spreading. Stamens 4, short-exserted, the 2 pairs equal or nearly so, the anthers small, the connective short, the pollen sacs 2, spreading, dark purple. Ovary deeply lobed, the style appearing more or less basal from a deep apical notch. Style short-exserted, with 2 unequal branches at the tip. Fruits dry schizocarps, separating into 2–4 nutlets, these 1.3–2.0 mm long, more or less globose, rounded at the tip, the surface orangish brown to reddish brown, with a network of fine nerves or slender, low ridges, glabrous. 2n=40. June–September.

Scattered, mostly south of the Missouri River (native of Asia; introduced widely in the eastern U.S. west to Minnesota, Nebraska, Texas; also Canada, Europe). Bottomland forests, banks of streams and rivers, bases of bluffs, fens, and seeps; also fallow fields, pastures, cemeteries, railroads, roadsides, and moist, disturbed areas.

This species has a long history of use in Oriental cuisine and traditional medicine, and as a source of a red dye. Steyermark (1963) noted that the seed oil has been important in the manufacture of lacquer, artificial leather, paper umbrellas, printer’s ink, and waterproof clothing, and that in the United States it has been used as a substitute for linseed oil in the varnish and paint industries. It apparently was introduced into the United States in the late 1800s by Asian immigrants and was soon adopted by local residents in the Appalachians and Ozarks as a potherb and seasoning (Potts, 1996). However, Burrows and Tyrl (2001) reported that ingestion of the plant by livestock results in respiratory symptoms known as panting sickness and acute respiratory distress syndrome (ARDS), which can also lead to fatalities. Overconsumption in humans can cause similar poisoning. The plants contain a complex mixture of aromatic compounds (resulting in a pronounced disagreeable odor when the foliage is crushed), including cyanogenic glycosides, but apparently the toxicity is caused by several volatile furan ketones. As with many biochemically active plants, dosage is the key to distinguishing between a pleasant food flavorant and a toxic plant.

Over time, a complex series of infraspecific taxa has been described based on Asian materials, but many of these taxa appear to relate more to cultivated selections than to wild variants (Yu et al., 1997). Two main groups of variants generally are recognized. Plants called var. crispa (Benth.) W. Deane are characterized by dark brownish purple leaves with somewhat more finely toothed margins. Sometimes the leaf blades also are crisped along the margins. This variety is cultivated primarily as a food additive and for dye. Green plants with relatively coarsely toothed leaf margins are referable to var. frutescens and are cultivated mainly for their seed oils. Selections from both of these groups are used medicinally. However, in the United States, there appears to be a breakdown of these characters, in that plants with purplish leaves having relatively coarsely toothed margins are encountered and vice versa. In a genetic analysis of cultivated and weedy wild plants in Japan, Nitta and Ohnishi (1999) concluded that many of the wild plants may have arisen through past interbreeding of cultivated variants. For practical purposes, it does not appear reasonable to formally treat infraspecific taxa in the present work.