1. Vitex negundo L. (vitex, chaste tree, hemp tree)

Map 2008

Plants shrubs or small trees. Main stems or trunk 1 to more commonly few to several, 100–500 cm long, erect or ascending, branched, the bark light brown to grayish brown, relatively smooth, but with scattered raised lenticels. Twigs mostly sharply 4-angled, reddish brown to dark brown with pale lenticels, but the surface more or less hidden by a dense, scurfy to felty covering of minute, spreading unbranched hairs, these often intermixed with sparse, longer hairs. Winter buds ovoid, angled to a sharply pointed tip, somewhat flattened, the 2–4 outer scales obscured by dense felty hairs. Leaves opposite, mostly long-petiolate (10–60 mm), the petiole unwinged. Leaf blades palmately compound with 3–9 leaflets, these 1–15 cm long, 0.5–4.0 cm wide, mostly stalked (the basalmost leaflets usually markedly shorter than the others and often sessile or nearly so), lanceolate to elliptic or occasionally oblanceolate, tapered at the base, tapered to a sharply pointed tip, the margins variously entire to irregularly toothed or with slender pinnate lobes, the upper surface dark green, glabrous or more commonly sparsely to moderately short-hairy, sometimes only along the main veins, some of the hairs sometimes minutely gland-tipped, the undersurface appearing gray, densely pubescent with minute, spreading hairs, rarely glabrous, also with sparse, inconspicuous, sessile glands. Inflorescences terminal panicles, the short branches with clusters of several to numerous flowers mostly along the upper side. Bracts scalelike. Calyces actinomorphic, 2.5–3.5 mm long, lacking a lateral projection, symmetric at the base, bell-shaped, the tube more or less 5-nerved, the nerves obscured by dense, short hairs, shallowly 4-lobed, the lobes similar in size and shape, narrowly triangular, not spinescent, not becoming enlarged at fruiting. Corollas 6–8 mm long, zygomorphic, the tube funnelform, obliquely 2-lipped to about the midpoint, the upper lip shorter and 2-lobed, white to pale lavender (rarely darker), the lower lip longer, with a large central lobe and 2 short lateral lobes, pale lavender to more commonly purple or bluish purple, often with a yellow spot at the base (mouth), the outer surface (and mouth) densely grayish short-hairy. Stamens 4, exserted, all similar in size, the filaments attached in the corolla tube, the anthers small, the connective very short, the pollen sacs 2, appearing angled from their tips, dark purple. Ovary unlobed, the style appearing terminal. Style exserted, with a pair of slender, spreading branches at the tip. Fruits fleshy, more or less globose to very slightly obovoid (sometimes truncate to very slightly concave at the tip) drupes 3–5 mm in diameter, the outer surface dark brown to black, glabrous (sometimes with a few hairs toward the base and slightly glandular toward the tip), the stone 4-celled. 2n=26, 32, 34. June–October.

Introduced, uncommon, widely scattered (native of Asia, Africa, Madagascar, Pacific Islands, introduced sporadically in the U.S.). Sand savannas and edges of mesic to dry upland forests; also old fields, fencerows, roadsides and disturbed areas.

This species was first reported for Missouri by Yatskievych and Summers (1993). It formerly was distributed by the Missouri Department of Conservation for use in wildlife plantings and also occasionally is cultivated as an ornamental in Missouri. Several varieties have been named, differing in leaflet shape and degree of toothing or lobing, as well as density and narrowness of the inflorescences (S.-l. Chen and Gilbert, 1994). The plants that escape from cultivation in temperate North America range from var. negundo (with leaflets entire or nearly so) to var. heterophylla (Franch.) Rehder (with leaflets having irregularly toothed and/or lobed margins. However, the infraspecific taxonomy of the species requires further study, as many intermediates are known between some of the named variants and the various characters said to separate the taxa sometimes do not appear well-correlated.

Vitex negundo is often confused with another commonly cultivated species, V. agnus-castus L., which is native to southern Europe and western Asia and escapes sporadically throughout the southern United States (farther north along both seaboards) and elsewhere in the world. As characterized by Wann and Akeroyd (2000), this species differs from V. negundo in: the stronger aromatic scent of the crushed foliage; usually slightly larger corollas (6–10 mm), more shallowly lobed calyces with broadly triangular lobes; and smaller fruits (2–3 mm in diameter). Vitex agnus-castus also has inflorescences that tend to be few branched from near the base, with the branches more strictly spicate than those of V. negundo, only the lowermost nodes having noticeably stalked flower clusters.