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Rainy Side Gardeners' Featured Book
Viburnums
Flowering Shrubs for Every Season
by Michael A. Dirr
With their abundance of flower, handsome foliage, robust constitution, and frequently stunning fruits, viburnums are among the most beautiful and versatile hardy shrubs available to gardeners. Yet despite these outstanding qualities, there has never been an entire volume devoted to them – until now. In this definitive, comprehensive, generously illustrated guide, internationally renowned woody plant expert Michael Dirr provides a wealth of information about every species and cultivar worthy of horticultural consideration. Dirr details each plant's height, spread, foliage, habit, floral characteristics, fruits, special traits such as fragrance or attractive bark, hardiness, origin, cultural needs, and overall garden appeal. These finely judged appraisals make it easy for the gardener or designer to choose the right plant for the right situation.
Excerpt from this book: Seldom recognized as a viburnum because of the maple-shaped leaves, this wide ranging, colonizing, suckering, native species dwells on the forest floor, often in the suffocating shade of noble trees. Definitively, it will never ascend to the garden acceptance and use of V. carlesii and V. dentatum, but it does have a niche in naturalized landscapes. The fall color is exceptional — in shades of fluorescent pink and rose-red to grape-juice purple-red — and effective for an extended period in October–November. I have experienced V. acerifolium in the wild from Maine to Indiana to Georgia, always as a spreading-colonizing shrub, 2 to 3 (occasionally 4 to 6) feet high, usually inhabiting slopes and hillsides. In mid October 2003, Bonnie and I chanced upon a thicket of vibrating fall color near Wiscasset, Maine. We were lumbering down a slope to find an open view of the marsh for photographic purposes. I believe this viburnum actually followed us from Georgia to Maine.
The 2-to 5-inch-long and -wide leaves, blue-green to dark green, are often 3-lobed with prominent jagged serrations and impressed veins. I have also observed plants with unlobed leaves. Leaves have black dots on the lower surface. Flowers, off-white, nonoffensive odor (offensive on a Florida provenance), in 1- to 3-inch-wide, flat-topped cymes, open in early May (Chapel Hill, North Carolina; 25 April 2006 in Athens, Georgia). On occasion, pink-budded flower forms occur. Unfortunately, as the flowers mature, the pink fades to white. Fruits, almost camouflaged among the foliage, are black, ellipsoidal, 1/3-inch-long drupes. I seldom see them persisting into fall and suspect that they are taken early by the birds.
Any woodland, organic, humusy, well-drained soil is suitable for cultivating V. acerifolium. Truly remarkable that in my travels, I cannot remember a plant in a cultivated, man-intervened, garden setting. Cultivars are occasionally listed but are doubtfully sufficiently unique from the species to warrant purchasing. Prospers quite contentedly, in the wild, from New Brunswick to Florida, west to Minnesota and Texas. Zones 3 to 7(8). Introduced 1736. Viburnum atrocyaneum, C. B. Clarke
Observed in only a few gardens by the author and rather refined compared to its big-leaf brethren. Evergreen leaves, ovate to ovate-elliptic, serrate, acute at apex, cuneate to rounded at base, 2 to 3 inches long, 1¼ to 1¾ inches wide, with 5 to 7 vein pairs, emerge bronze to purplish, eventually dark green, and finally bronze-purple-green in winter. Petiole is 1/3-inch-long, maroon, glabrous, with the color extending to the midvein below. Completely glabrous, which is seldom true for viburnums; whorled leaf arrangement (3 at a node) occasionally occurs. The May–June flowers (29 May 2006, Hillier Arboretum) are greenish white and are followed by ellipsoidal, 1/5-inch-long, steel-blue fruits. Develops into a small, 3- to 4-foot-high and -wide shrub, although I observed a 15-foot-high and -wide specimen at Hillier in 1999. This plant was multi-stemmed, vase-shaped, with rounded crown. Lancaster (1989) reported a 20-foot-high plant in China. Appears to tolerate sun and partial shade. Small plants reside at the J. C. Raulston Arboretum and in the superb garden of Charles Keith in Chapel Hill, North Carolina. Zones 7 and 8. Native to the Himalayas. Cultivated plants are derived from Kingdon-Ward's 1931 collection. Viburnum awabuki, K. Koch
Heavenly taxonomic nightmare! in recent years, this taxon has been assigned variety (subspecies) and cultivar status under V. odoratissimum, and maintained as a legitimate species. Leaves, when crushed, do not have the foul odor of V. odoratissimum. It has also been listed as V. macrophyllum and V. japonicum (a legitimate species). The uniqueness of this taxon, compared to its so-called brethren, deserves a legitimate designation. I have observed gigantic old plants in Augusta, Georgia, and in Raleigh and Chapel Hill, North Carolina, exceeding 20 feet in height and exhibiting no mature growth characteristics comparable to V. odoratissimum and V. japonicum. The narrow, elliptic, 3- to 7-inch-long, ½-to 2-inch-wide leaves, as thick as orange peel, mirror-reflective upper surface, toothed on the margins, are beautiful throughout the seasons. In fact, the foliage is the principal reason to utilize the plant. It makes a great screen or group planting and can be pruned into a respectable hedge. The leaves are so large and thickish that the cut edges may look the worse for wear after pruning.
Bonnie and I had a plant of 'Chindo' given to us by J. C. Raulston of North Carolina State University. This, in reality, does not appear vegetatively different from the species, except Raulston mentioned observing "large pendulous masses (6 to 10 inches in diameter) of bright red fruits hanging in the 15-foot-tall plant like ornaments on a Christmas tree." 'Chindo' and the species are initially shy flowering and fruiting. I observed the white, fragrant flowers in late May on a large, 20-foot-high specimen at the J. C. Raulston Arboretum in Raleigh. I suspect that fruit set is minimal because the species is largely self-sterile and requires another seedling or clone to effect cross-pollination. The plant at the J. C. Raulston Arboretum produced a fair display of 1/3-inch-long, red, oval fruits in August 2005.
The species is reliably cold hardy in Zone 7; however, the foliage may be discolored or injured when temperatures drop below 0°F. In the early 1980s, temperatures dropped to between -5°F and -10°F in Griffin, Georgia, and large plants were killed to the ground but did resprout. The species requires well-drained soil and is remarkably drought tolerant once established. I have observed it prospering in sandy and clay-based soils in sun and shade. In fact, extremely dense-foliaged specimens develop in the shade of pine trees in Georgia.
For grouping or screening, or as a bold-textured specimen plant, V. awabuki is a topflight choice. Remember, pruning is a requisite to keep it in bounds. Matures 15 to 25 feet high, 10 to 15 feet wide. Ancient trees in Japan are recorded as growing 66 feet high. Zones 7 to 9(10). Native to Korea, Japan, eastern China, and Taiwan. Grows in evergreen forests on hills and in valleys in warm coastal areas at altitudes of 30 to 2,500 feet. See Lancaster 2000. Cultivars & varieties
'Variegata' is spectacular with milk-white marginal variegation. Unfortunately, the chimera is unstable. This means that all green, all white, and white-margined leaves can occur. For the collector who has time to remove the stray reversion shoots. Viburnum betulifolium, Batal. — Birchleaf Viburnum
I had only read about this species and dreamed of the magnificent red fruit displays that are typically described. Then in Trewithen Gardens, Cornwall, on a chilly February day, I chanced upon several 15-foot-high plants — the fruits still persistent. Since that initial encounter, sightings have increased, and I ponder why the species is not more common in American commerce.
Typically, a large shrub with arching branches. The 2- to 4-inch-long, 1½- to 3-inch-wide, dark green leaves resemble those of a birch: apex acuminate, base rounded, sharply serrate, with 7 to 9 vein pairs, veins prominent with tufts of hairs in axils below, and petiole about ¾ inch long. On the leaf underside are a pair of pitted glands, one on either side of the midrib near the base. The white flowers occur in 2- to 4-inch-wide, 7-rayed cymes in May–June in England; they were in full flower 6 May 2006 at the Sarah P. Duke Gardens, Durham, North Carolina. My notes state, "Fragrance not bad" on the Sarah P. Duke plant. The bright red fruits are spectacular, each ¼ inch long, ovoid in shape, and long persistent. For maximum fruit expression, plant several seedlings for cross-pollination. A well-drained, slightly acid soil is best. Provide full sun to partial shade. Excellent plant for the back of the border or as a loose screen or grouping. In England I witnessed plants 10 feet high and 15 feet wide at Hillier, 15 feet high and wide at RHS Wisley, 15 feet high and wide at Hinton Ampner, and 10 feet high and wide ('Marchant') at RHS Hyde Hall. Lancaster (1989) noted a 13- by 13-foot specimen in China. Zones 6 and 7(8). Native to China, Taiwan. Cultivars & varieties
'Hohuanshan' was described by Crûg Farm as a small, deciduous, well-branched shrub to 13 feet high in the wild. New leaves emerge deep bronze and are followed by white flowers and bright red fruits. Their collection was from Tayuling, Taiwan, at approximately 10,000 feet.
'Marchant' has smaller leaves than the species and pinkish fruits.
'Trewithen' is a heavy-fruiting selection. I believe that this was derived from the plants I saw at Trewithen Gardens. Viburnum bitchiuense, Mak. — Bitchiu Viburnum
This species is closely allied to V. carlesii and absolute identification is not easy. The habit is looser, with more slender stems, smaller leaves, and smaller, pure-white flowers. Leaves, dull, dark blue-green, 1 to 3 inches long, 1 to 2 inches wide, may turn dull reddish purple in fall; however, I have observed plants with sheeny, blue-green leaves. Leaves emerge by late March at the J. C. Raulston Arboretum, Raleigh, North Carolina. The flowers, in 2- to 3-inch-wide, hemispherical cymes, open in late March–early April (Athens, Georgia). The emerging buds are pink, opening white, and sweetly fragrant. Fruits are approximately ¼ inch long, ripening red to black. The species is taxonomically difficult to put one's arms around. Plants labeled as such may be V. carlesii. In our Georgia trials, a wild-collected V. bitchiuense by Dan Hinkley flowered profusely as a small plant, with inflorescences to 4 inches in diameter. The leaves are dull gray-green and larger than typical V. bitchiuense. In my observations, V. bitchiuense, to the envy of V. carlesii, appears more heat tolerant. The fact that V. ×juddii (V. carlesii × V. bitchiuense) performs better in Zones 7 and 8 of the south than V. carlesii supports these contentions. Not fussy about soils as long as they are well drained. Site in full sun to partial shade. Will grow 8 to 10 feet high and wide. Zones 5 to 7. Native to Japan and Korea. Introduced 1911. Viburnum ×bodnantense, Stearn — Bodnant Viburnum
My affection for this group of hybrids between V. farreri and V. grandiflorum, named after Bodnant Garden in Wales where they originated, ebbs and flows with the seasons. From fall to spring, fragrant flowers are often present. The floral effect is not overwhelming, but the fragrance and unique timing more than compensate. I grew V. farreri in our Urbana, Illinois, garden, where it prospered; V. ×bodnantense in Georgia, where it perished. This was my fault for I sited it in full sun and a dryish location. 'Dawn', in other southern gardens, properly sited, has performed with dignity. The foliage is akin to V. farreri, 2 to 4 inches long, 1 to 2 inches wide, bronze when emerging, later medium green, narrowly oval, tapering at the ends and regularly toothed except at the base. Described in European literature as having good autumn color, this has not occurred under my watch in the United states. The fragrant flowers appear from the naked branches in cymes that are 1 to 2 inches wide by approximately 1 inch high. The buds are pink (varying degrees) and open to lighter colors (pink to almost white). The red fruits mature in summer (June in England) and in my experience are limitedly produced. They eventually turn black at maturity, but I have yet to witness this latter color stage. The habit is cumbersome and stiff, upright in youth, eventually somewhat rounded. Certainly more appealing when fully foliaged than naked-stemmed. Will grow from 8 to 10(15) feet high and wide, or wider. Behemoth-like specimens are common in english gardens. Quite adaptable, sun and shade, with reasonable moisture. Grows from Chicago, Illinois, to Atlanta, Georgia. Zones 5 to 7, 8 and 9 on West Coast. Cultivars & varieties
The three cultivars — 'Charles Lamont', 'Dawn', and 'Deben' — have separate origins. The original crosses were made by Charles Lamont in 1933 at the Royal Botanic Garden, Edinburgh, using V. grandiflorum as the maternal parent. Initially, none were considered worthy of naming.
Flowers open over an extended period, so if injured by cold, another spurt follows. There is a surreal, mystical aura to the flowers, and as I traipsed around the Hillier Arboretum in February and March in the dank and cold, I had the "feeling" that I was being watched. Can plants see?
Certainly worthwhile plants for the winter garden. Their oafishness can be masked by groundcover shrubs and perennials like Sarcococca, Danae, Helleborus, and Skimmia.
'Charles Lamont'. A seedling with brighter pink flowers (than 'Dawn') and a more free-flowering nature. Leaves are the largest of the three cultivars (the V. grandiflorum trait). An upright-spreading, stiff, coarse plant, 15 feet high and 10 feet wide, grew at Hillier in 1999. A 15- to 18-foot-high specimen grew at RHS Wisley on 25 May 2006.
'Dawn' was derived from V. farreri × V. grandiflorum (1934) by Charles Puddle, head gardener at Bodnant Garden, Wales. The flowers are pink with dark purple-pink anthers. This is the most common form in cultivation in the United States. Witnessed a 12- by 8-foot plant with great foliage at Hillier on 2 July 1999.
'Deben' appeared as a chance seedling at Notcutts Ltd., England. The buds are pink, opening apple-blossom pink, and fading to white. Flower clusters are larger than those of 'Dawn'. May be a cross with V. farreri 'Candidissimum' as one parent. The flowers show cold injury (browning) more so than 'Dawn' and 'Charles Lamont'. There was an upright-spreading form, 12 feet high by 10 feet wide, at Hillier in 1999. Viburnum bracteatum, Rehd. — Bracted Viburnum
Even for the advanced gardener, this is a difficult species to properly identify. Consider it a souped-up version (72 chromosomes, an octaploid) of V. dentatum with glossier, thicker-textured leaves. Otherwise I see little difference between the two species, and, within the complex V. dentatum, individual plants that resemble V. bracteatum do appear. I have grown a selection, 'Emerald Luster', for ten years in the UGA trials that is 10 feet by 8 feet in outline: a respectable haystack. This lone specimen is tightly branched and, in foliage, lustrous dark green. Over the years, I have observed a number of plants labeled as V. bracteatum, but I am never absolutely convinced. The basis for the epithet is the presence of distinct bracts that subtend the inflorescence. Leaves, 2 to 5 inches long, 1½ to 3 inches wide, almost rounded at times, with 5 to 6 vein pairs, ending in coarse dentate teeth, turn yellow to bronze in fall. Leaves are pubescent on impressed veins below; petiole is about ½ inch long and pubescent. Leaves display remarkable heat tolerance and hold up better than those of most named V. dentatum cultivars in Athens. Flowers, white and malodorous, open in early to mid May (Athens), in 2- to 3(5)-inch-wide, flat-topped cymes. On 'Emerald Luster' the flowers are borne in profusion, producing a striking contrast to the glossy dark green foliage. Tolerates sun and shade (will be more open in shade) in well-drained soils. Excellent drought tolerance as evidenced by ten years in Georgia trials without flinching. Makes a great screen, shrub border, or naturalizing and wildlife shrub. Unique in that the purple-blue-black fruits (at least of 'Emerald Luster') occur in profusion without cross-pollination, meaning a single plant is self-fruitful. Easy to root from cuttings and to grow in containers. The species grows to 10 feet high and wide. A 15-foot-tall plant of the species resides in the Hillier Arboretum. Zones 6 to 8. Native to the southeastern United States. Viburnum buddleifolium, C. H. Wright — Woolly Viburnum
Common neither in literature nor in gardens, V. buddleifolium serves as a lure for the collector. The fuzzy, bunny-ear leaves, resembling those of Buddleia, are the benchmark for identification. Leaves in outline resemble V. rhytidophyllum, 4 to 6(8) inches long, 1 to 2 inches wide, shallowly toothed with 8 to 10 vein pairs, and a woolly pubescent petiole that is approximately ½ inch long. Leaves softly pubescent above, gray-felted below. Leaves tend toward semi-evergreenness with at least those below the terminal bud persisting in Zone 7. The stems and buds are covered by fine pubescence.
Pink buds give rise to white flowers in April (10 April 2004 in Chapel Hill, North Carolina), in 2- to 4-inch-wide, 7-rayed cymes. I kept smelling the flowers, expecting the off-odor, but was unable to detect anything, sweet or foul. I checked the field notes from my study leave at Hillier in 1999 and read the abbreviated passage, "No floral fragrance, April 13." The flowers are reminiscent of V. lantana but occur before the new leaves develop: the entire effect rather rickety. This is by no means a dainty plant, and habit is distinctly upright, to 10 feet high and greater. Usually taller than wide. Noted a dense, 10- by 6-foot plant with clean foliage at Hillier, 1 July 1999; 10- to 12-foot-high plant in Chapel Hill, North Carolina. Fruit, oval, red to black, average ½ inch long. A parent of V. ×rhytidocarpum. Deer will browse. Zones 6 and 7. Native to central China. Introduced in 1900 by E. H. Wilson.
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