4. Cornus florida L. (flowering dogwood)
floridum (L.) Raf.
Map 1609, Pl.
trees or rarely shrubs 3–15 m tall, usually occurring as solitary
individuals. Twigs reddish brown to reddish gray or green, moderately to
densely appressed-hairy, the pith usually tan. Bark relatively deeply fissured,
the ridges becoming divided into irregularly polygonal to oblong plates, dark
gray to brown. Leaves opposite, positioned mostly toward the tips of the
branches, the petiole 0.3–1.2 cm long. Leaf blades 5–12 cm
long, 3–8 cm wide, ovate to broadly elliptic or occasionally elliptic-obovate,
rounded, angled, or short-tapered at the base, angled or more commonly tapered
to a sharply pointed tip, the surfaces sparsely to densely pubescent with
mostly appressed, straight, T-shaped hairs when young, the undersurface
sometimes also with longer, more or less spreading, V-shaped or Y-shaped hairs
along the main veins, sometimes becoming glabrous or nearly so at maturity, the
lateral veins (4)5–7 pairs, these relatively evenly spaced.
Inflorescences dense heads subtended by 4 showy petaloid bracts, these
2.5–5.0 cm long, broadly obovate to nearly circular or somewhat
heart-shaped, shallowly notched at the tip, white or rarely pink, the flowers
sessile or nearly so. Sepals fused below the midpoint, the lobes
0.5–1.0 mm long. Petals 3–4 mm long, narrowly
oblong-lanceolate, greenish yellow. Style 3–4 mm long, relatively
slender, not broadened toward the tip. Fruits 7–14 mm long, ovoid to
ellipsoid, red (sometimes turning black with age). Stone strongly longitudinally
veined but smooth or shallowly and inconspicuously grooved. 2n=22.
common in the Ozark and Ozark Border Divisions north locally to Shelby and Marion Counties; also in the Crowleys Ridge Section of the
Mississippi Lowlands Division (eastern U.S. west to Kansas and Texas; Canada, Mexico). Mesic to dry upland forests, savannas, edges of glades, bases,
ledges, and tops of bluffs; less commonly banks of streams and rivers, margins
of sinkhole ponds, and bottomland forests; also pastures, old fields, and
Cornus florida is the official state tree
of Missouri (and also Virginia). It is among the showiest of early
spring-flowering trees in the understories of Missouri forests, beginning to
flower slightly later than but overlapping the pink flowers of redbuds (Cercis
canadensis, Fabaceae). The red fruits are an important autumn and winter
food source for migrating songbirds and small mammals. Steyermark (1963) noted
that Native Americans prepared a red dye from the roots and that the bitter
inner bark was used as a quinine substitute to treat malaria. The wood has been
shaped into many products, including shuttles, golf clubs, mallets, tool
handles, wedges, spindles, pulleys, knitting needles, roller skates, and
dogwood also is one of the most popular of ornamental trees in gardens, prized
for its showy bracts before the leaves appear, checkered bark, graceful habit,
and red fall foliage. Rare pink-bracted individuals have been called f. rubra
(Weston) E.J. Palmer & Steyerm. and are popular in horticulture. Other
cultivars, including some with the bracts pinkish- to reddish-tinged toward the
margins, also have been developed by plant breeders.
flowering dogwood is threatened throughout much of its range by dogwood
anthracnose, a disease caused by the fungus Discula destructiva Redlin,
which attacks some members of the group of dogwoods with showy inflorescence
bracts. The disease was first diagnosed in the 1970s in both the northwestern
(on C. nuttallii Audubon) and northeastern (on C. florida) United States, and by the 1990s it had spread throughout the range of the host species.
Symptoms include blotches and small spots with purple margins on the leaves and
twigs, worsening in wet years and developing into branch diebacks. The tree
weakens and dies after usually 1–3 years. The geographic origins of
this disease are not known, and it was first described as new to science as
recently as 1991. Attempts to link it to C. kousa F. Buerger ex Miq.
trees imported from China have not been successful, and speculation that a
shift in some aspect of the continents climate might have caused an
expansion in the range of a previously undiscovered native fungus also has not
been substantiated. For a summary of the pathology of this disease and its
affect on C. florida, see the excellent review by Daughtrey (1993).
Dogwood anthracnose has yet to be documented from wild dogwood populations in Missouri, but it has been recorded from south-central and west-central Illinois (Schwegman
et al., 1998), and unconfirmed reports of trees with anthracnose-like symptoms
have been recorded from elsewhere in the Midwest.