7. Ligustrum
L. (privet)
(Yatskievych and Summers, 1991)
Plants shrubs
(small trees elsewhere), sometimes evergreen or semi-evergreen. Trunks few to
several, ascending, sometimes arched, the bark grayish brown to gray, thin,
relatively smooth, but with raised leaf scars and lenticels. Twigs relatively
slender, variously yellowish green to gray, brown, or nearly black, glabrous or
hairy, more or less circular in cross-section, the leaf scars raised and the
lenticels conspicuous and raised. Terminal buds ovoid to conic-ovoid, with
scales that are sharply pointed at the tips, the axillary buds similar to the
terminal ones, but smaller. Leaves opposite or occasionally subopposite, mostly
short-petiolate, the petioles of the largest leaves 1–16 mm long. Leaf blades
simple, 1–8 cm long, 0.5–2.5 cm wide, oblong-elliptic to elliptic,
oblong-ovate, or less commonly lanceolate to ovate, angled or tapered (rarely
rounded or shallowly notched) to the bluntly to sharply pointed tip, rounded or
angled to broadly angled at the base, the margins entire (sometimes minutely
hairy), the upper surface green to dark green, glabrous, the undersurface
slightly lighter green to yellowish green, glabrous or hairy, often also
inconspicuously gland-dotted. Inflorescences terminal, few- to more commonly
many-flowered, variously ascending to spreading or nodding panicles
(occasionally reduced and nearly racemose) 1.5–10 cm long developing after the
leaves, the lower branch points with small, leaflike or scalelike bracts, the
flowers mostly with slender stalks 1–5 mm long (occasionally some of them
sessile), moderately but unpleasantly fragrant. Calyces truncate at the tip
(unlobed or sometimes appearing slightly wavy) or with 4 very shallow lobes
1.5–2.0 mm long, the lobes irregular, blunt or toothlike. Corollas 4-lobed to
about the midpoint or less, 5–12 mm long, trumpet-shaped, the lobes oblong to
oblong-ovate, white or occasionally cream-colored. Style 1–2 mm long, with a
pair of ascending branches at the tip or more frequently the fused stigmas
appearing as a club-shaped mass. Fruits berrylike drupes, 5–8 mm long, globose
to broadly ellipsoid, green to olive green, turning bluish black or black,
glabrous, sometimes slightly glaucous. About 45 species, Europe, Africa, Asia
south to Australia.
Many species are
grown in cultivation for their foliage in hedges, as screens or as specimen
plants. The heavily scented flowers of Ligustrum were described by
Mabberley (1997) as having an unpleasant, ammonia-like or fishy smell (caused
by methylamine) that reportedly can taint the honey of honeybees that visit the
flowers. Species of Ligustrum are considered toxic to livestock and
humans, but there are conflicting reports on how poisonous the various species
may be. Terpenoid glycosides, especially ligustrin derivatives of oleanolic
acid, are suspected as the chemical basis of intoxication (Burrows and Tyrl,
2001). Symptoms are mostly gastrointestinal, including stomach and intestinal
irritation, vomiting, and diarrhea, but also may progress to paralysis of the
limbs, fluid in the lungs, and rarely death.
Privets are
popular in horticulture as background shrubs, windbreaks, hedges, and specimen
plants. A number of other Ligustrum species in addition to those treated
below are cultivated in the United States, including L. amurense
Carrière (Amur privet), L. japonicum Thunb. (Japanese privet), L.
lucidum W.T. Aiton (glossy privet), and L. quihoui Carrière
(waxy-leaved privet). Cultivars are available with variegated leaves of green
and white or green and yellow.
The inclusion by
Steyermark (1963) of only L. ovalifolium and L. vulgare (as an
excluded species) for the state has led to the misidentification of some
Missouri specimens. Additional collections of naturalized plants are needed to
more accurately determine the species occurring in the state and their
respective distributions. Hardin (1974) and K. A. Wilson and Wood (1959)
pointed to a need for further taxonomic work on the genus. The following
key is adapted from Hardin’s work and requires flowering material for accurate
determinations.