4. Cornus florida L. (flowering dogwood)

Cynoxylon floridum (L.) Raf.

Map 1609, Pl. 369 f–h

Plants small 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. April–May.

Scattered to 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 roadsides.

Unfortunately, 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.