Know Your Natives – Rough Leaf Dogwood

Rough Leaf Dogwood (Cornus drummondii) of the Dogwood (Cornaceae) family is a small, deciduous tree with opposite leaves, open clusters of small white flowers, and striking, decorative white fruit. The genus name derives from the Latin for “horn” in apparent reference to the hardness of the wood. The specific epithet recognizes Scottish botanist Thomas Drummond (1790-1835) who collected plant specimens from the western and southern U.S. The species occurs from eastern Texas to southeast South Dakota, east to Alabama and Ohio. In Arkansas, occurrence is mostly statewide with a notable gap in the counties of the Gulf Coastal Plain––perhaps explained by undercollecting. Habitats include various dry to wet soils on sunny and shaded sites, such as woodlands, woodland openings and borders, stream banks, fence rows and abandoned fields. Rough Leaf Dogwood is abundant along the Arkansas River.

Trees grow to 15-20+ feet tall from shallow, spreading roots that sucker to produce clonal trees. Spacing of trees in a colony may be tight or open, as determined by the age of the colony, shading, and rockiness of soil. Trees on more sunny sites develop a dense, broad, leafy crown, while crowded or shaded trees become tall with only a few erect branches. Some branches may exhibit a fast rate of growth (1+ feet per year) reaching for light. Epicormic branches may sprout directly from the trunk.

Photo 1: Trees on sunny sites have dense leafy twigs. To maintain a single trunk, suckers of this tree are removed. Yellow flowers at lower right are those of Yellow Crownbeard.

New twigs, initially pale green with dense, short pubescence, become reddish on their sunny side over several years before becoming gray and glabrous with small white lenticels that roughen with age. Twigs are straight. As they mature, the thin bark becomes shallowly fissured, splitting into small rectangular plates aligned along the branch. Fissuring becomes more pronounced on expanding trunks, with plates remaining relatively small and fairly tight. Lenticels eventually become lost on the rough texture of the bark.

Photo 2: Trunks of a colony are of various ages and sizes. New suckers may add trees beyond the perimeter of a colony or within a colony. These fissured trunks have characteristic small rectangular plates aligned with the trunk.

Overwintering, short, slender twigs (1-2 inches long) have small, valvate (2 scales in a praying-hand position) buds. With spring, twigs develop a terminal pair of opposite leaves and one to several pairs of lateral leaves. Most new-twig growth, both vegetative and reproductive, originates from terminal buds. Lateral buds often remain dormant or produce short-lived, stubby twigs. A reproductive twig’s terminal leaves subtend a floral cluster, as well as axillary buds. Vegetative twigs’ terminal pair of leaves subtend a single terminal bud. On sunnier sites, tips of robust twigs become congested with branches and inflorescence peduncles, making this architecture rather obscure.

Photo 3: Pairs of opposite twigs grow from the tips of the previous year’s fertile twigs, forming a Y-shape. Fertile and vegetative twigs become reddish on their sunny side over several years before becoming gray. Photo – November 19.
Photo 4: As paired twigs develop into branches, the branch on the upper side tends to become dominant. With the aging of branches, lenticels become less noticeable. Lowest branches in this photo are 6 feet above ground. (See lenticels in Photo 15.)
Photo 5: These trees, on a steep rocky slope, are in the understory. When falling oaks bent some trees, adventitious buds sprouted along the trunks and developed into erect stems.

The opposite, simple, ovate to elliptic leaves are about 4-6 inches long (including a 1-inch petiole) and 2-3 inches wide, with wedge-shaped (cuneate) to rounded or oblique bases and acuminate to abruptly acuminate tips. Leaves are green above and lighter below, with the sunny side of petioles becoming reddish. Pinnate venation is recessed above and expressed below, the secondary veins arching toward, but not reaching, the leaf apex. Both surfaces are pubescent, with moderately scabrous hairs above and softer hairs beneath––the upper surface feels slightly rough. Twigs and petioles are also hairy. In fall, leaves become orangish to purplish with distal leaves somewhat persistent.

Photo 6: Sunny sides of the pubescent twigs and petioles become reddish. A single terminal axillary bud occurs on the vegetative twig (left) and a pair occurs on the fertile twig (right) after the inflorescence has been shed. Bud scales are valvate. Photo – September 20.
Photo 7: Bases of the ovate to elliptic leaves may be oblique and apexes may be acuminate to abruptly acuminate. Veins are prominent on upper and lower surfaces. Well-spaced secondary veins are arcuate. Photo – September 29.
Photo 8: Dense, softly scabrous pubescence of upper surface (left) feels slightly rough, while villous hairs on lower side (right) feel soft. Hairs are not tightly appressed (as compared to Gray Dogwood – see below). Photo – November 5.

The inflorescence, from May to June, to 4 inches wide and 2 inches long, comprises a broad, rather flat-topped panicle on one or a few floral stalks. Fifty to eighty small white to creamy white flowers terminate the twigs of the current year. The pubescent branching stalks and pedicels redden as the fruits mature to white.

Photo 9: Long-stalked flower clusters are terminal on current year’s twigs. At upper left, with vigorous growth, short infertile secondary twigs may grow from the base of the inflorescence. Photo – May 10.

Flowers, about ¼ inch wide, have 4 sepals, 4 petals, 4 stamens (filament + anthers), and one pistil (ovary + style + stigma). Sepals, petals (about 3/16 inch long), and stamens (also about 3/16 inch long) are attached at the summit of the inferior ovary. The oblong anthers, set see-saw fashion at the narrowing tip of the filaments, are elevated higher than petals and stigma. The flattened stigma is at the apex of the erect style. A prominent nectary encircles the base of the style.

Photo 10: The firm oblong-lanceolate petals are wide-spreading to the point of being down-flexed. Straight filaments position anthers above the post-like style. Photo – May 15.
Photo 11: Flower clusters, terminal on current year twigs, are flat-topped to slightly domed. Anthers, stigma and nectary ring are a slightly darker color than petals. Stamens drop as flowers begin to fade.
Photo 12: All flowers of panicles bloom and fade at the same rate. Panicles are wider than long. Leaves are loosely folded along their midribs. Photo – May 25.

In August and September, the immature green drupes become white and fleshy as the floral stalks, floral branches, and pedicels become reddish. Each drupe, a slightly flattened sphere about ¼ inch across, contains a single, smooth stone. A dark, rimmed depression with persistent sepals at the fruit’s apex marks the former attachment point of the petals and stamens.

Photo 13: Fruits have a central apical scar that persists from the base of the petals and stamens. Stalks and branches of the inflorescence become red as fruits mature. Photo – July 29.
Photo 14: Mature white, flattened-spherical fruits contrast with the reddish floral branches and green leaves. Tiny persistent sepals can be seen on the rim of the scar. Photo – August 22.
Photo 15: Fruits are a favorite of many song birds as well as ground-dwelling birds. Light colored lenticels can be seen on the twig extending to right. Photo – September 14.
Photo 16: If fruits are not taken by birds, stalks dry and fruits shrivel. Fruits contain a single spherical stone. Minute sepals persist on some fruits (see red arrow). Photo – October 17.

In regard to gardens, Rough Leaf Dogwood has a strong suckering tendency and, for a single-trunk tree, would need continual sucker control. It will grow in the understory, but, depending on degree of shading, its structure may be sparse and flowering and fruiting may be limited. This small tree is ideal for a larger naturalized area, for property barriers, and bank stabilization. Its leafy growth, flower clusters, fruits and fall foliage can be showy. Fruits are highly prized by a wide variety of birds and mammals.

Photo 17: Fall foliage can be colorful with leaves at the ends of twigs persisting for up to a month. White arrow (lower left) points to the apex of a fertile twig where the infructescence has dropped off and a pair of axillary buds are present. Photo – November 8.

Five other dogwoods occur in Arkansas: 1) Alternate Leaf Dogwood (Cornus alternifolia) with alternate or whorled leaves and twigs as well as panicles of small white flowers and blue fruits, 2) Flowering Dogwood (Cornus florida) with showy white bracts surrounding a densely clustered flower head and red fruits, 3) Stiff Dogwood (Cornus foemina) with panicles of small white flowers and blue fruits, 4) Silky Dogwood (Cornus obliqua) with panicles of small white flowers and blue fruits, and 5) Gray Dogwood (Cornus racemosa) with panicles of small white flowers and white fruits. Of these, Rough Leaf Dogwood is most likely to be confused with Gray Dogwood which has a similar growth habit and inflorescence. However, Gray Dogwood is more shrub-like, has panicles that are about as tall as wide, and its leaves are less pubescent, with smooth upper adaxial surfaces and abaxial hairs being appressed.

Article and photographs by ANPS member Sid Vogelpohl

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