5. Viburnum L. (viburnum, blackhaw, arrowwood)
Plants shrubs or
small trees. First-year twigs 1–3 mm thick, the pith solid. Winter buds
various, appearing naked or more commonly with 2 valvate (the margins touching
but not overlapping) or 4 overlapping scales. Leaves with short or relatively
long, unwinged or narrowly winged petioles, none perfoliate. Stipules absent or
present, if present then 2–10 mm long, usually slender, sometimes partially
fused to the basal portion of the petiole. Leaf blades simple, elliptic,
oblong, ovate, or almost circular, the margins finely to coarsely toothed
(3-lobed in V. opulus). Flowers in dense, flat-topped panicles, usually
appearing as compound umbels, terminal on the branches, occasionally reduced to
a loose, umbellate cluster, the branch points with small, linear to narrowly
triangular bracts that are mostly shed by flowering, the individual flowers
usually subtended by minute, paired bractlets that are mostly shed early in
flower development. Calyx lobes 0.3–3.0 mm long, variously shaped. Corollas of
the marginal (sterile) flowers of the inflorescence sometimes enlarged and
slightly zygomorphic, those of the fertile flowers 2–4 mm long, actinomorphic,
more or less saucer-shaped or rarely somewhat bell-shaped with a broadly
cup-shaped tube 1–2 mm long and a spreading, (4)5-lobed portion 3–8 mm in
diameter (measured across the top of the flower), the lobes rounded, white,
sometimes fading to pale yellow. Style absent or nearly so, the ovary often
broadly conical-tapered at the tip, the deeply 3-lobed stigma appearing
sessile. Fruits berrylike drupes, more or less spherical to more commonly
oblong-ellipsoid, red to bluish black. Nutlet 1, 6–11 mm long, oblong-ovate to
elliptic in outline, flattened, one or both sides often ridged or with a pair
of longitudinal grooves, sometimes appearing longitudinally folded, the surface
variously smooth to somewhat warty, yellowish brown to reddish brown or nearly
black. About 175 species, North America to South America, Europe, Asia to Java.
Species of Viburnum
are important for wildlife food, and the fruits of some species also have been
eaten by man, raw, cooked, or processed into preserves and jellies. Many Asian
species of Viburnum have been introduced into horticulture, and several
have been reported to escape in states to the east of us. However, only two Old
World species, V. lantana and V. opulus, are known to have become
established in Missouri. Some of the native species are planted widely as well,
and they sometimes escape in areas outside their native ranges.
The sections of Viburnum
are well defined (at least in Missouri), but the species within the sections
often are difficult to distinguish. For this reason, the sections are noted in
the key to species below. Users should note that leaf descriptions in the
species treatments below apply to most of the stems on a given plant, including
flowering/fruiting stems. However, leaves of vigorous leading shoots, rapidly
elongating root suckers, or juvenile plants sometimes differ strikingly in
their longer, narrower, and more acute appearance, often with fewer veins and
fewer, smaller marginal teeth.