Viburnum
Viburnum is a diverse genus comprising approximately 150 to 300 species of flowering plants within the Adoxaceae family. These plants predominantly manifest as shrubs or small trees, often cultivated for their highly fragrant flowers and ornamental appeal. Viburnums typically thrive in temperate regions of the Northern Hemisphere, with a few species found in other areas. Characteristically, Viburnum leaves are simple and grow oppositely along the stem, providing a distinctive visual trait. The flowers of Viburnum are arranged in clusters, featuring five lobes and reproductive structures that contribute to their unique appearance.
These plants produce drupes—fruits with a fleshy outer layer surrounding a hard seed—ranging in color from red to black, which attract various birds during the winter months. Viburnums are known for their resilience, tolerating conditions such as drought and deer, and are commonly used for creating natural privacy screens or hedges. They grow at a moderate rate, reaching heights of 2 to 20 feet (0.6 to 6 meters) and widths of 5 to 12 feet (1.5 to 3.6 meters), making them versatile for landscaping. Overall, Viburnums require minimal maintenance, enhancing their appeal among gardeners and homeowners alike.
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Viburnum
Viburnum (capitalized and italicized) is the name for a genus of about 150 to 300 species of flowering plants that are part of a broader taxonomic family called Adoxaceae. The word viburnum (lowercase) may also refer to any plant that belongs to the genus Viburnum. Viburnums usually take the form of shrubs or small trees. Several species grow highly fragrant flowers, and they are often cultivated as ornamental plants. Viburnum leaves serve as an important food source for the larvae of many species of moths and butterflies. Viburnums are typically native to temperate regions of the Northern Hemisphere, but a few species grow outside these areas.
Overview
Viburnums formerly belonged to the taxonomic family Caprifoliaceae, which includes honeysuckles, weigelas, and snowberry bushes. However, new evidence indicating a greater divergence between viburnums and other species of Caprifoliaceae caused scientists to play the viburnums into a new family alongside the moschatel, a flowering perennial plant, and the elderberry bushes. Together, the Caprifoliaceae and Adoxaceae families belong to the taxonomic order called Dipsacales.
Because viburnums can vary dramatically in appearance, size, and habitat, they are instead grouped by their DNA composition. However, viburnums can be visually characterized by their leaves, fruits, and flowers. Viburnum leaves grow in an opposite pattern, meaning that leaves appear symmetrically on opposite sides of the plant stem. Viburnums have simple leaves with undivided blades. (These contrast with compound leaves, which have a series of smaller leaves called leaflets that make up each leaf.)
Viburnums' fruit is a drupe, a form of fruit with a fleshy external shell surrounding a hard stone in the middle. The fruit of viburnums is typically rounded with a hard, bony layer covering the seed. Viburnum flowers are clustered together into corymbs in which the outermost flowers have longer stems than flowers in the middle so that all flowers are even with one another. The florets grow in clusters, typically at the ends of branches. Viburnum flowers have five lobes, five stamens, a three-cell ovary, and a three-lobed stigma, which make up the reproductive organs of the plant.
As ornamental plants, viburnums have been cultivated to have several shapes, sizes, and flower colors. In the United States, viburnums grow most successfully between hardiness zones 2 and 9, which means that the most cold-resilient species can withstand an average minimum temperature of –50°F (– 46°C). Most ornamental viburnums are cultivated to reach between 2 and 20 feet (0.6 and 6 meters) in height and between 5 and 12 feet (1.5 and 3.6 meters) in width. They grow moderately quickly at a rate of 1 to 2 feet (0.3 to 0.6 meters) per year. They are resistant to deer and drought and are valuable in creating natural privacy screens or hedges for homes. Their flowers typically range from white to pink. Their fruit, which varies in color from red to black, attracts a variety of birds and will last well into winter, making them a showier winter plant than many other types of bushes. Viburnums require a minimal amount of work to maintain.
Bibliography
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Clement, Wendy L., et al. "A Chloroplast Tree for Viburnum (Adoxaceae) and Its Implications for Phylogenetic Classification and Character Evolution." American Journal of Botany, vol. 101, no. 6, 2014, pp. 1029–49.
Diir, Michael A. Viburnums: Flowering Shrubs for Every Season. Timber Press, 2007.
Friis, Else Marie, et al. "Bruniales, Apiales, Paracryphiales, and Dipsacales." Early Flowers and Angiosperm Evolution. Cambridge UP, 2011, pp. 385–6.
Spriggs, Elizabeth L., et al. "Temperate Radiations and Dying Embers of a Tropical Past: The Diversification of Viburnum." New Phytologist, vol. 207, no .2, 2015, pp. 340–54.
Swaciak, David. "Guide to Identifying Viburnums." Cornell University, 4 Aug. 2016, www.hort.cornell.edu/vlb/key/index.html. Accessed 1 Mar. 2017.
"Viburnums." Missouri Botanical Garden, www.missouribotanicalgarden.org/gardens-gardening/our-garden/notable-plant-collections/viburnums.aspx. Accessed 1 Mar. 2017.
Williamson, Joey, et al. "Viburnum." Clemson Cooperative Extension, Clemson University, 20 Feb. 2015, www.clemson.edu/extension/hgic/plants/landscape/shrubs/hgic1075.html. Accessed 1 Mar. 2017.