1. Pachysandra procumbens Michx. (Allegheny spurge)

Map 1397

Plants perennial herbs, monoecious, with long-creeping, branched rhizomes, more or less evergreen. Aerial stems 10–40 cm long, spreading to ascending, sparsely to densely (especially toward the tip) pubescent with short, curled hairs, green to nearly white, sometimes purplish-tinged. Leaves alternate, mostly toward the stem tips, mostly long-petiolate. Stipules absent. Leaf blades 3–9 cm long, simple, ovate to broadly obovate or nearly circular, rounded to more commonly sharply pointed at the tip, tapered at the base, the margins with relatively few coarse teeth above the midpoint and also minutely hairy, the surfaces sparsely to moderately and minutely hairy along the veins, the upper surface dark green but often with lighter mottling, the undersurface lighter green. Inflorescences relatively dense spikes or spikelike racemes (the staminate flowers sessile, the pistillate flowers sometimes short-stalked), 5–12 cm long, axillary from the lowermost aerial stem nodes. Flowers actinomorphic, hypogynous, the staminate flowers numerous and positioned toward the inflorescence tip (sometimes also 1 or 2 at the very base), each subtended by 1 small sepal-like bract; the pistillate flowers usually 1–7 and positioned toward the inflorescence base, each subtended by a series of 7 or more small scalelike to sepal-like bracts. Calyces of 4 free sepals (sometimes more in pistillate flowers), 3.5–5.0 mm long, ovate to broadly ovate, rounded to sharply pointed at the tip, usually reddish- or purplish-tinged, the margins minutely hairy. Corollas absent. Staminate flowers with usually 4 stamens, these opposite the sepals and exserted from the calyx, the filaments white, the anthers red to reddish purple, attached below the midpoint of the outer side. Pistillate flowers with 1 pistil, this superior, usually with 3 carpels and apically 3-lobed, each carpel with 2 locules, the surface densely and minutely hairy. Ovules 6, the placentation more or less axile. Styles usually 3, each with a linear stigmatic region along the inner side toward the tip. Fruits capsules, 12–16 mm long, ovoid to nearly globose, apically 3-lobed, the surface densely and minutely hairy, dehiscing circumscissilely near the base. Seeds 1 per locule, 3.0–4.5 mm long, ovate in outline, triangular in cross-section, with a small outgrowth (caruncle) at one end, the surface smooth, black, shiny. 2n=24. March–May.

Introduced, known thus far from a single collection from Warren County (southeastern U.S. west to Kentucky and Louisiana; introduced farther north and west). Mesic upland forests.

The presence of the Warren County population was long known to members of the Webster Groves Nature Study Society and monitored regularly by Midge Tooker, who graciously showed the site to the author. The occurrence is seemingly natural, but the presence in the vicinity of a few other nonnative species, such as Tsuga canadensis, suggests the former presence of an old homesite.

The Asian P. terminalis Siebold & Zucc., a close relative, also is commonly cultivated as a groundcover. It differs from P. procumbens in its somewhat narrower leaves, terminal inflorescences, and 2-carpellate flowers. Pachysandra terminalis has escaped from cultivation sporadically in the northeastern United States and adjacent Canada, and eventually it may be located in Missouri.