Stems: Arrowwood is a multi-stemmed upright shrub growing to 9 feet high and almost the same in diameter making a rounded mass with arching branches.
Twigs are slender, angled with ridges, sometimes downy when young and then hairless with age. Buds are green to brown with several scales. Older stems are grayish with fissures showing the underlying reddish-brown tissue. The surface has warty protrusions.
Leaves are opposite, on short stalks without stipules, rounded to lanceolate in shape (broadest just below the middle), up to 4 inches long. Margins have sharp coarse teeth. Tips vary from pointed to rounded. Dark green above, dull under with some hair in star shaped tufts beneath and on the stalks. Leaves turn reddish in the fall. The leaves subtending the flower cluster have stalks at least 9/32 inches (7mm) long; the leaf stalk does not have a stipule; both of those characteristics separates the species from V. rafinesquianum.
The inflorescence is a branched, flat-topped cluster (a corymb), 2 to 4 inches wide, at the terminal end of new stem growth. Each cluster will have 5 to 7 flat-topped sub-groups. At the base of the corymb is a small green bract, one for each branch, then each corymb branch has its own bract.
Flowers: The 5-part flowers are small, less than 1/4 inch wide with the corolla tube spreading its 5 white lobes outward to a bell shape. The inside of the tube is sometimes with hair. There are 5 protruding stamens with yellow anthers. The stigma of the style is three-lobed. The base of the style has fine hair. The calyx is short, green to yellow-green on the five pointed lobes of the tip.
Fruit: The flowers mature to a rounded drupe (berry-like fruit), up to 1/4 inch in diameter that is green initially and turns bluish-black at maturity and bears a single seed. Seeds germinate only after having a cold moist period, followed by a warm moist period, followed by another cold moist period, each period of at least 60 days. If sown, they will germinate in the second year.
Habitat: Arrowwood grows best in loamy soil with adequate moisture in full sun to partial sun in open woods, wood edges and stream banks. It tends to sucker from the base but in an open space, forms a nice rounded form. It has a fibrous root system and is easily transplanted. Propagation of new plants is from seed or vegetative cuttings.
Names: In the never ending quest for specificity, botanists have recently moved the Viburnum genus into the Adoxaceae plant family, which is a small group of 5 genera of shrubs that have opposite leaves, mostly 5-petaled flowers that produce a small drupe. Minnesota authorities have made this change, USDA has not yet. The genus Viburnum is the Latin name for a European species of this genus. The species name dentatum, means 'toothed' - as per the leaves. In Eloise Butler's day the plant was also known as Viburnum pubescens and several other names now consolidated into the present classification. The common name of Arrowwood refers to the Native American use of straight stems for arrows. The author name for the plant classification - 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: There are a number of species of Viburnum and varieties of this plant. The full name of this species is Viburnum dentatum L. var. dentatum - not native to the state. The Arrowwood native to Minnesota is V. rafinesquianum, Downy Arrowwood, where the leaf stalks have stipules and the leaf stalks subtending the flower cluster are 9/32" (7mm) or less in length.
Below: 1st photo - Flowers occur in a branched flat-topped cluster, a corymb, with each cluster having 5 to 7 flat-topped groups. 2nd photo - The 5-part flowers are small, less than 1/4 inch wide with the corolla tube spreading its 5 white lobes outward to a bell shape; 5 extended stamens with yellow anthers.
Below: Each corymb of the inflorescence will have 5 to 7 flat-topped groups. At the base of corymb is a small green bract, one for each branch, then each branch cluster has its own bract. Older stem are grayish with fissures showing the underlying reddish-brown tissue. The surface has warty protrusions.
Above and below: Flowers mature to a rounded drupe (berry-like fruit), up to 1/4 inch in diameter that turns bluish-black at maturity and bears a single seed. Below 2nd photo: The underside of the leaf has hair along the main rib and down to the stalk.
Below: 1st photo - The calyx is green, shading to yellow-green on the 5 pointed lobes. 2nd photo - Stalked leaves have coarse sharp teeth and prominent veins. 3rd photo - Buds are green-brown with a few scales. Twig may be downy.
Below: A four year old plant in bloom.
Notes: Eloise Butler introduced this plant to the Garden in 1910 from a source in Osceola, WI. In 1912 she brought in plants from Kelsey's Nursery in South Carolina. In her day the plant was known as Viburnum pubescens. This species is not native to Minnesota but is found in the eastern half of the United States with the northern range from Iowa east to IL, IN, OH, PA and NJ. It has been planted in various locations in the metro area and does well here. There are recent proposed changes to the family structure for this genus, moving the Viburnums from Caprifoliaceae to Adoxaceae. This has not yet universal but Minnesota authorities at the DNR and the U of M Herbarium have made the change.
There are six Viburnums found in Minnesota outside of gardens. Four are native - American Cranberrybush (Highbush Cranberry), V. opulus var. americanum; Squashberry, V. edule; Downy Arrowwood, V. rafinesquianum; and Nannyberry, V. lentago. Two are introduced - European Cranberrybush, V. opulus var. opulus, and Wayfaring-tree, V. lantana.
Pests: Viburnums are subject to damage from the Viburnum Leaf Beetle, Pyrrhalta viburni, a native of Europe, which first was found in North America in 1947. The larvae feed on the leaves. Female beetles hollow out an egg cavity on the twigs to hold their eggs which over-winter and hatch in the spring. Certain species of Viburnum are more susceptible than others to the pest with V. dentatum, V. rafinesquianum, V. nudum, and V. opulus var. americana being most susceptible. These species will succumb to the pest in 2 to 3 years of infestation unless the eggs are destroyed. For just a few plants, cut off twigs with egg cases in late fall after the beetles have died.[Detailed PDF]
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"