Contributed by B.A. Sorrie & A.S. Weakley
A genus of about 160-200 species, shrubs and small trees, largely temperate, and primarily in Asia and North America. There remain a number of taxonomic problems, particularly in the Viburnum dentatum complex; the treatment and key for that group is provisional. Dirr (2007) discusses the genus in detail from a horticultural perspective.
ID notes:Leaves vary in shape in some taxa more than in others; we have allowed for some of this variation in the key, but readers should expect that some specimens will not key cleanly, especially rapidly-growing vegetative shoots. Petiole length of leaves varies considerably, even with those possessing “short” petioles. However, by measuring only the petioles of the first leaves below an inflorescence one reduces the chances of misidentifications greatly. Warning: even in some of the “long” petioled taxa, one may occasionally encounter unusually short petioles; therefore it is wise to examine several twigs. Density of pubescence and glandularity of leaves, petioles, and inflorescences varies more in some taxa than in others; we have allowed for some of this variation in the key, but readers should expect that some specimens will not key cleanly, especially vegetative shoots. Stipitate glands are usually very short, especially those on leaf veins; a 10× lens may not be adequate to see them clearly. It is our belief, based on thousands of specimens examined and years of fieldwork, that most Viburnum tend to lose pubescence, and perhaps glandularity as well, as the season progresses.
Ref: Clement et al. (2014); Clement et al. (2021); Dirr (2007); Ferguson (1966a); Floden & Saxton (2020); Landis et al. (2021); McAtee (1956); Spriggs et al. (2019a); Spriggs et al. (2019b); Weckman et al. (2002); Winkworth & Donoghue (2005). Show full citations.