downy arrowwood

(Viburnum rafinesqueanum var. affine)

               
Conservation Status

IUCN Red List

not listed

 

No image available

 

NatureServe

N5 - Secure

SNR - Unranked

Minnesota

not listed

Nativity

Native

Occurrence

Common

Habitat

Moderately moist to dry. Woodlands. Full sun, partial sun, or deep shade.

Flowering

Late May to early July

 
Flower Color

Creamy white

 
Height

3 to 9

 
 
Identification

Downy arrowwood is a medium-sized shrub that rises on multiple stems from a woody, spreading root system. It occurs in North America east of the Great Plains from Quebec to Manitoba south to South Carolina and Tennessee. It is common in northern and eastern Minnesota, mostly absent in the southwestern quarter of the state. It grows in moderately moist to dry upland woodlands in full sun, partial sun, or deep shade. There are two varieties of downy arrowwood, rafinesqueanum and affine. The ranges of both varieties appear identical, and many collected specimens have intermediate characteristics. Nevertheless, the varieties are generally, though not universally, accepted. Both varieties occur in Minnesota.

Downy arrowwood (var. affine) can be 3 to 9 tall and up to 13 16 (3 cm) in diameter at the base, but in Minnesota it is usually no more than 6 in height. The roots have buds which may sprout and form above-ground stems (suckers). When conditions permit, it forms colonies.

The bark on the lower stem is gray and wrinkled, and it sometimes, though rarely, peels in papery sheets. On older stems it becomes gray or grayish-brown to reddish-brown and fissured. On the upper stem and branches the bark is gray or grayish-brown and smooth.

Young twigs are green to reddish-green, round in cross section, and hairless. They have widely scattered white pores (lenticels). When cut at a diagonal, the soft tissue visible in the center of the twig (pith) is solid. The twigs are brown to reddish-brown in their second year. The buds egg-shaped to cone-shaped, slightly flattened, and hairless. They have two pairs of overlapping scales. They are not sticky or are only slightly sticky.

The leaves are opposite, undivided (simple), and deciduous. They are attached to the twig on a short, light green to red leaf stalk (petiole). The petiole averages (10 mm) long, one-fifth to one-tenth as long as the blade, but can be to ¾ (4 to 20 mm) long. The petiole is grooved on the upper (ventral) side, and and hairless. It is not winged and there are no projecting glands near the attachment to the leaf blade. At the base of each petiole there is a pair of leaf-like appendages (stipules). The stipules are green to reddish-green, narrow with almost parallel sides (linear), and partially fused to the base of the petiole. They are to (3 to 9 mm) long, usually shorter than the petiole.

The leaf blades are relatively thin and papery, egg-shaped to broadly lance egg-shaped, 1½ to 4 (4 to 10 cm) long, 1¼ to 2¾ (3 to 7 cm) wide. They are rounded or shallowly heart-shaped at the base and narrowly angled to a point at the tip with straight or concave sides along the tip. They are pinnately veined. The lateral veins are straight, evenly spaced, and end in a tooth at the margin. There are often 3 to 5 secondary veins near the base on each side. The upper surface is green and sometimes hairless but usually has scattered, unbranched hairs. The lower surface is pale green and is hairy just along the main veins, at least in the angles (axils), but is otherwise hairless. The margins have 6 to 10 (rarely up to 14) coarse teeth on each side. The leaves turn an attractive dull purplish-red to dull purple with red highlights in the fall.

The inflorescence is a dense, rounded, shallowly convex, ¾ to 2 (2 to 6 cm) in diameter, branched cluster (cyme) of 30 to 100 flowers at the ends of the current-year branches. The cymes have 4 to 7 main branches. They may be almost stalkless or have inflorescence stalks (peduncles) up to 2 (6 cm) long. The flowers on the margin of the cyme are fertile and are similar in appearance and size to the interior flowers.

Each flower is about ¼ in diameter. There are five sepals, five petals, five stamens, and no style. The sepals are green, fused for most of their length into a minute cup (calyx), and separated at the tip into five minute, triangular lobes. The petals are creamy white, broadly egg-shaped to elliptical, and 1 16 to (1.5 to 3.0 mm) long. The stamens have white filaments and tan anthers. They are 1 16 to (1.5 to 4.0 mm) long and extend beyond the petals. There is a three-lobed, stalkless stigma on a short disk (stylopodium) at the top of the ovary. The flowers appear in late May to early July. They have a fragrance that may appeal to insects but does not to humans.

The fruit is an edible, juicy, berry-like, oblong to ellipse-shaped or nearly spherical, somewhat flattened, ¼ to (6 to 9 mm) long drupe. It is green initially, becoming bluish-purple to purplish-black at maturity. It is not covered with a whitish, waxy bloom (glaucous). The fruit contains a single ¼ to 5 16 (6 to 8 mm) stone. The stone is somewhat flattened and is shallowly grooved on both sides. The fruit ripens in early August to early September.

 
Similar
Species

Downy arrowwood (Viburnum rafinesqueanum var. rafinesqueanum) petioles are hairy, especially along the groove, and shorter, averaging ¼ (6 mm) long but no more than (15 mm) long. They are about one-tenth as long as the blade and usually shorter than the stipule. The leaf underside is uniformly hairy.

 
Distribution Distribution Map  

Sources: 4, 7, 29, 30.

 
Comments

What’s in a Name?
This species was named for the 19th century polymath Constantine Samuel Rafinesque, who made important contributions to botany and zoology. It was published in 1820 as “Viburnum rafinesquianum”. The species epithet is a latinized correctable misspelling of the honoree’s last name. The corrected name is “Viburnum rafinesqueanum”. Many authoritative sources use the corrected spelling, but about the same number use the name as originally published. Which is correct? An argument can be made for either spelling.

Taxonomy
The genus Viburnum was formerly included in the Caprifoliaceae (honeysuckle) family. Based on a molecular phylogeny study published in 2005, it was moved to the Adoxaceae (moschatel) family.

 
Taxonomy

Family:

Adoxaceae (moschatel)

 

Genus:

Viburnum (viburnum)

 
Parent

downy arrowwood (Viburnum rafinesqueanum)

 
Synonyms

Viburnum rafinesquianum var. affine

 
Common
Names

downy arrow-wood

downy arrowwood

downy-leaf arrow-wood

Rafinesque’s arrowwood

   

 

 

 

 

 

 

Glossary

Axil

The upper angle where a branch, stem, leaf stalk, or vein diverges.

 

Calyx

The group of outer floral leaves (sepals) below the petals, occasionally forming a tube.

 

Cyme

A branched, flat-topped or convex flower cluster in which the terminal flower opens first and the outermost flowers open last.

 

Drupe

A fleshy fruit with a single hard, stone-like core, like a cherry or peach.

 

Glaucous

Pale green or bluish gray due to a whitish, powdery or waxy film, as on a plum or a grape.

 

Lenticel

A corky, round or stripe-like, usually raised, pore-like opening in bark that allows for gas exchange.

 

Linear

Long, straight, and narrow, with more or less parallel sides, like a blade of grass.

 

Peduncle

In angiosperms, the stalk of a single flower or a flower cluster; in club mosses, the stalk of a strobilus or a group of strobili.

 

Petiole

The stalk of a leaf blade or compound leaf that attaches the leaf blade to the stem.

 

Pinnately veined

With the veins arranged like the vanes of a feather; a single prominent midvein extending from the base to the tip and lateral veins originating from several points on each side.

 

Pith

The spongy cells in the center of the stem.

 

Stigma

In plants, the portion of the female part of the flower that is receptive to pollen. In Lepidoptera, an area of specialized scent scales on the forewing of some skippers, hairstreaks, and moths. In Odonata, a thickened, dark or opaque cell near the tip of the wing on the leading edge.

 

Stipule

A small, leaf-like, scale-like, glandular, or rarely spiny appendage found at the base of a leaf stalk, usually occurring in pairs and usually dropping soon.

 

Sucker

A basal shoot rising from the roots or from a bud at the base of a shrub or tree.

 

Winged leaf stalk

A leaf stalk with a leaf-like or membrane-like extension along both sides.

       
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Created: 11/17/2019

Last Updated:

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