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.