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.