1. Viburnum dentatum L. (southern arrowwood)

V. dentatum var. deamii (Rehder) Fernald

Map 1437, Pl. 337 c–e

Plants shrubs 1–3 m tall. Bark firm, not peeling, relatively smooth to finely roughened or warty on younger branches, gray or grayish brown to reddish brown. Winter buds ovoid-conical, slightly flattened, with 2 pairs of overlapping scales, glabrous, not or only slightly sticky. Stipules sometimes present but usually shed early, partially fused to the basal portion of the petiole, linear, hairy and glandular. Petioles 16–28 mm long, unwinged, moderately pubescent with short, pale, branched to stellate hairs, especially on the upper surface, lacking prominent glandular swellings near the tip. Leaf blades (5–)7–11 cm long, (5.5–)6.5–10.0 cm wide, unlobed, relatively thin and papery, broadly elliptic to broadly ovate or nearly circular, rounded to truncate or shallowly cordate at the base, rounded or broadly angled to a usually bluntly pointed tip, occasionally abruptly contracted to a short-tapered, more or less sharply pointed tip, the margins coarsely toothed with the teeth 1–3 per cm, 14–21 on each side, the upper surface moderately pubescent along the veins and on the tissue between the veins with mostly unbranched or few-branched hairs, occasionally some of the hairs appearing stellate, the undersurface moderately to densely pubescent along the veins and on the tissue between the veins with mostly branched or stellate hairs, often with 3 or 4 secondary veins on each side crowded near the base of the midvein, pinnately veined above the base, the secondary veins straight, often dichotomously branched but not forming a network, extending to the leaf margin, each branch ending in a tooth. Inflorescences short- to long-stalked, with (3–)5–7 primary branches, these moderately hairy and with minute, stalked glands, the marginal flowers fertile and similar to the other flowers. Ovaries glabrous or occasionally with a few scattered, minute, stalked glands, the tapered, stylelike tip densely short-hairy. Fruits 7–10 mm long, ellipsoid, oblong-ovoid, or nearly spherical, purplish blue to bluish black, not glaucous. Nutlet 6.0–7.5 mm long, yellowish brown. 2n=36, 54, 72. May–June.

Uncommon, known thus far only from Shelby County (eastern U.S. west to Iowa and Texas). Bottomland forests and mesic upland forests.

Viburnum section Odontotinus comprises about 45 species that are widespread in eastern North America and Eurasia. The approximately six species native to North America are mostly part of a taxonomically confusing polyploid complex centered on V. dentatum. Most of these taxa have been called arrowwood because the straight branches were used in the past to make arrow shafts. They are difficult to distinguish, especially when mature fruit and flowers are lacking, and they have been treated variously as 6–10 or more species or as about 4 species with several additional varieties. The whole complex deserves more detailed biosystematic study. Missouri plants have been called var. deamii, a name applied to a series of morphologically poorly differentiated octoploid (2n=72) populations from western Pennsylvania to Missouri that differs from var. dentatum in the frequent production of stipules and the presence of scattered stipitate glands on the undersurface of the leaves.

Recently collected specimens from the margins of a disturbed woodland in Columbia (Boone County) were referred to this species by their collectors (Paul McKenzie and Tim Smith). These shrubs have the pubescence of the leaves mostly confined to the veins and vein axils (but with sparse hairs on the intervening tissue) and the inflorescence branches only sparsely pubescent. Plants with similar morphology have been called V. dentatum var. indianense (Rehder) Gleason, a name that has been applied to uncommon plants occurring in southern Illinois and Indiana (Gleason and Cronquist, 1991). It is possible that the Boone County materials represent an escaped cultivar or hybrid involving V. dentatum, but in their overall morphology they also seem close to V. recognitum. They are included in the concept of that species in the present treatment but might in fact be treated better as a hybrid derived from these two taxa (see Egolf [1962] for further discussion). They require further study.