1. Cornus L. (dogwood)
Plants shrubs or
small trees (occasionally rhizomatous herbs elsewhere). Leaves usually opposite
(alternate in C. alternifolia). Winter buds ovoid, with usually 2
scales. Twigs with white to brown pith lacking diaphragms (cross-partitions).
Leaf blades with the margins entire or less commonly minutely wavy, the upper
surface green to dark green, the undersurface usually pale green (except sometimes
in C. foemina), the secondary veins strongly arched toward the leaf tip,
becoming irregularly fused toward the leaf margin. Inflorescences terminal on
the branches, short, broad panicles or usually compound umbels, in C. florida dense heads surrounded by 4 showy petaloid bracts. Flowers perfect (imperfect
elsewhere). Calyces with the free portion consisting of 4 small, triangular
lobes 0.1–2.0 mm long or a minute, low rim. Petals 4, inserted along
the margin of the nectar disc, white, cream-colored, or greenish yellow.
Stamens 4, the slender filaments 3–4 mm long, attached along the margin
of the nectar disc, the anthers 1.0–1.5 mm long, narrowly oblong,
attached toward the midpoint. Pistil of 2 fused carpels but 1 carpel sometimes
aborting during development, the ovary frequently hairy, with 1 or 2 locules.
Style 1, stout or slender, the stigma often 2-lobed. Ovule(s) 1 or 2 (1 per
locule). Fruits ovoid to spherical, red, white, or dark blue. Stone 1- or
2-seeded, the seeds oblong, flattened. Forty to 65 species, North America,
South America, Europe, Asia, Africa.
In the past,
some botanists have treated Cornus in a narrower sense, with various
species groups segregated into 7–9 small genera (Murrell, 1993).
Because these groups are more closely related to each other than to anything
outside the genus, most botanists now regard them as subgenera of Cornus
(Eyde, 1987). There are two major groups within Cornus, one with red
fruits and large petaloid bracts subtending the inflorescence, and the other
with blue or white fruits and the inflorescence bracts minute or absent (Eyde,
1988; Fan and Xiang, 2001). Taxonomic relationships within the blue- to
white-fruited lineage are complicated by morphological intergradation and
apparent hybridization, in addition to many of the original taxon descriptions
having very brief, incomplete diagnoses and lacking designated type specimens.
Furthermore, the size and shape of the leaves, degree of pubescence, and color
of the twigs and fruits may be affected by exposure to sun and shade or other
environmental factors. Flower morphology is more or less uniform, but the
inflorescences vary from open panicles to compact, headlike clusters. For this
group, the present treatment tentatively follows that of Wilson (1965).
Cornus is prized for its hard wood, which has
been used in spears, daggers, and weaving shuttles. Additionally, several
species are cultivated in the Midwest as hedges, specimen plants, and as
ornamentals, especially cultivars with red or yellow stems. Dogwood fruits also
provide food for various mammals and birds and are recommended for wildlife
plantings. Various species are larval food plants for several groups of moths.
The European species C. mas L. (Cornelian cherry) produces delicious
fruits that are often prepared into jams and syrups. Steyermark (1963) noted
that Native Americans prepared a tobacco substitute from strips of the bark of
several species under the name kinnikinnick.