Downy Arrowwood is a native perennial shrub growing on multiple stems to 6 feet high. Stems are generally straight but spreading and the plant forms a nice shape. The bark on older stems is a mottled gray to reddish brown with some warty protrusions.
Twigs are straight, reddish brown, with buds that reddish-brown scales that have short hairs long the margins. The terminal buds are ovoid in shape, laterals similar. Leaf scars are v-shaped with 3 bundle scars.
The leaves are opposite, on short hairy stalks with a pair of stipules at the base. The leaf stalks subtending the flower cluster are 9/32 inch (7mm) or less in length. Leaves are egg to lance shaped, medium to dark green with prominent venation and slight to very hairy on the underside. Leaf edges have coarse pointed teeth at the end of each leaf vein, but less broad than the Southern Arrowwood. Tips are pointed and the bases usually have a slight heart-shape. Leaf size is to 2-1/2 inches long and 1-1/2 inches wide. Fall color is rose to maroon.
The inflorescence is a branched, compound cyme (cluster), 2 to 3 inches wide, at the terminal end of stems. Each cyme will have 5 to 7 flat-topped groups.
Flowers: The 5-part flowers are small, less than 1/4 inch wide with the corolla tube spreading its 5 creamy-white lobes outward to a bell shape. The inside of the tube is sometimes with hair. There are 5 protruding stamens with yellow anthers that are exerted from the corolla throat. The stigma is three-lobed. 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 flattened ellipsoid seed.
Varieties: See notes bottom of page.
Habitat: Downy Arrowwood prefers shade to partial shade, in well drained neutral less-fertile soils without excessive moisture - even dry conditions. It is very cold hardy.
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 rafinesquianum, is an honorary for Constantine Samuel Rafinesque, (1783-1840), European polymath who traveled in the United States, lived here many years, collected specimens, and published over 6,700 binomial names for plants. The author name for the plant classification, ‘Schult.’ refers to Josef August Schultes (1773-1831), Austrian Botanist who with Johann Jacob Roemer published the 16th edition of Linnaeus’ Systema Vegetabilum. The common name of Arrowwood refers to the Native American use of straight stems for arrows. "Downy" refers to the excess of hair on the leaves and leaf stalks of this species compared with Southern Arrowwood. An older name for this species is Viburnum affine.
Comparisons: The similar looking Southern Arrowwood, V. dentatum, has coarser teeth on the leaves, hair on the undersides of the leaf only on the main veins if at all, no leaf stipules and the leaf stalks subtending the flower cluster are 9/32 inch (7mm) or more in length. It is also a larger plant with arching stems.
Above: Terminal buds and laterals have reddish brown scales with fine hair on the scale margins. Bark on older stems is a mottled gray with raised warty protrusions showing.
Below: The flower cluster is 2 to 3 inches wide. Each flower has creamy-white lobes and 5 exerted stamens with yellowish anthers.
Below: Leaves have sharp coarse teeth. The underside usually has fine downy hair as does the leaf stalk. Note the pair of small linear stipules at the base of the leaf stalk.
Below: The short green calyx of the flower has 5 point lobes. Mature fruit is a 1/4 inch bluish-black drupe.
Below: Plants growing in the understory are usually no more that 6 feet high and have multiple stems.
Downy Arrowwood is not indigenous to the Garden, but has been in the Garden since the 1930s. Martha Crone noted it in bloom in 1938 (as Viburnum affine) and Cary George planted it in 1989. Downy Arrowwood is found in Minnesota in most counties of the state except the SW quadrant where it is found only sparsely. Two varieties are recognized within Minnesota: var. affine and var. rafinesquianum. The former has hairy leaf stalks and leaf stipules and the underside of the leaf is slightly hairy on the veins. Var. rafinesquianum has more hair on the leaf undersides and the leaf stalks are shorter than the stipules. In North America it is found from the Dakotas eastward the coast in the U.S. excepting Maine and the southern gulf coast states. In Canada it is known in Manitoba, Ontario and Quebec.
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. Another Viburnum that will grow nicely in Minnesota, but is not native to the area is Southern Arrowwood, V. dentatum.
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"