Michael A. Dirr, Ph.D.
Copyright © 2012

In the August, 2011, Nursery Management, a survey of 4,000 landscape professionals listed Viburnums as the number two most utilized plant after Buxus (1) and before Hydrangea (3). Viburnums are often tagged as utilitarian, functional, reliable garden denizens without the pizzazz of hydrangea. Viburnums have contributed to every Dirr garden and the newest currently houses 40 species and cultivars. I planted the first in fall 2010 in a sinuous border to screen the vegetable garden. A neighbor asked what was planted. Viburnum was the reply. He said . . . what? Such is the obscurity of my beloved Viburnums.

At the University of Georgia and now Plant Introductions, viburnum breeding has been a part of my program. Several of the new hybrids are discussed herein and shown in the presentation. Viburnum breeding requires patience for seeds are often doubly dormant and 2 to 3 years are required for seedlings to flower. Many of my selections are now 8 to 10 years old and not yet commercialized. Viburnums, like fine wines, require time. Dr. Egolf’s ‘Nantucket’ spanned 20 years before introduction. The cross was made in 1988; plant introduced in 2008.

Dr. Brent McCown, University of Wisconsin, and students hybridized V. carlesii × V. lantana with 171 clones via embryo rescue. To date, there are no introductions.

Michael Yanney, Johnson’s Nursery, Menomonee Falls, introduced Spice Island™ (‘JNSA’), Spiced Bouquet™ (‘J.N. Select’), and Sugar ‘n’ Spice™ (‘Select S’), all V. carlesii selections. Testing the three in Georgia and have yet to sense greatness. He also introduced V. dentatum Red Feathers® and V. trilobum Red Wing™.

Gary and Susan Ladman, Classic Viburnums, Upland, Nebraska, are true aficionados, and we correspond regularly. They have introduced ‘Copper Ridges’ (V. plicatum f. tomentosum) and ‘Prairie Classic’ (V. × jackii) and have the richest Viburnum offerings in the U.S.  Over 200 Viburnum taxa are in their inventory. Visit www.classicviburnums.com

Jim Zampini and Maria Zampini, Upshoot, list five V. dentatum, three V. plicatum, and two V. prunifolium that have been introduced. Roy Klehm, Beaver Creek Nursery, introduced three V. cassinoides, six V. dentatum, and one V. sieboldii. None resulted from controlled breeding and are row-run, chance seedling selections or branch sports. Gary Ladman’s great comment that the world does not need another V. dentatum with an additional tooth (serrations) along the margin rings true.

The greatest viburnum breeder was the late Dr. Don Egolf, USNA, who released 19 cultivars. ‘Nantucket’ (#20) released in 2008 is an evergreen with large, white, slightly fragrant inflorescences and outstanding heat tolerance. Parentage is ‘Eskimo’ × V. macrocephalum f. keteleeri. I have utilized ‘Nantucket’  in Georgia breeding with considerable success.

An abbreviated checklist of Viburnum species and cultivar facts, foibles, follies, and fables follows.

• Who can identify? Opposite leaves, drupaceous fruit (fleshy outer covering, hard inner).

• Approximately 150 species. Two new species described in Plantsman 10(4): 232-237, 2011- Viburnum fansipanense and V. hoanglienense, from northern Vietnam.

• Sum of parts constitutes great garden shrubs.

• No magic WOW factor.

• Utilitarian (functional) landscape elements.

• Classic Viburnums, Upland, NE, Gary Ladman, glclassicviburnums@rcom-ne.com; Gary is a viburnum scholar, as is Susan, his wife.

• Southern growers and retailers note that viburnums are a difficult sell.

• New introductions with potent pizzazz are essential to move the genus forward in the commercial market.

Best of Best

Fragrant Flowers

• Viburnum bitchiuense—Parent of V. × juddii; more heat tolerant than V. carlesii; performed well in Georgia trials, pink buds open to white, sweetly scented flowers. My original plant was wild-collected by Dan Hinckley. Hybridized with an open-pollinated ‘Nantucket’ evergreen seedling 69852-02-06 (now Pearlific™) to yield a spectrum of habits and foliage, several with outstanding fall color. Also, 69852-01-06 has large, lustrous dark green, semi-evergreen leaves, turning wine-red, 4 to 5” diameter, white, lacecap flowers, on a 4’ by 4’, 6-year-old plant.

• Viburnum ×burkwoodii—American Spice™ (-20°F), ‘Mohawk’, ‘Park Farm Hybrid’; high heat tolerance primarily due to V. utile parentage.

• Viburnum ×carlcephalum ‘Cayuga’

• Viburnum carlesii—‘Aurora’ and ‘Diana’; Spice Island™ (‘JNSA’), Spiced Bouquet™ (‘J.N. Select’), and Sugar ‘n’ Spice™ (‘Select S’) are more restrained growers with the typical fragrant flowers from Johnson’s Nursery, Menomonee Falls, WI. Yet to prove impressive in Georgia trials.

• Viburnum farreri, ‘Candidissimum’—pretty white flowers.

• Viburnum ×juddii—better than V. carlesii for heat tolerance.

• Hybrids of ‘Park Farm Hybrid’ × V. m. f. keteleeri produced all snowball seedlings, but with minimal fragrance.

• Open-pollinated ‘Mohawk’ seedlings are floriferous, red-budded, opening white, fragrant with superior summer foliage, red-purple in fall and restrained habit (6-7’) at 8 years of age.

• Have grown numerous V. ×burkwoodii and V. ×carlcephalum seedlings to flower with nothing better than the parents.

• ‘Susy’, named by Gary Ladman after our youngest daughter, is an open-pollinated evergreen seedling of ‘Eskimo’ [(V. carlesii × V. ×carlcephalum) × V. utile], with supra abundant white flowers, red to black fruits, 6 to 7’ by 5’ after 8 years. Roots readily, grows off vigorously, and sets abundant flower buds as a small liner. The V. utile parentage is easily recognized.

Showy Flowers

• Viburnum plicatum types—‘Pink Sensation’, ‘Popcorn’ (f. plicatum); ‘Cascade’, ‘Molly Schroeder’ (pink rose) (f. tomentosum)

• Kevin Spellman, Wisconsin (?), sent photos and cuttings of an upright, broad-columnar, snowball flowered, self-sown seedling from his garden. Foliage is dark green, thick-textured and heat tolerant (like ‘Popcorn’). Seedlings of this selection display comparable foliage traits. Gary Ladman is producing this plant. Name under consideration is ‘Spellbound’.

• Most cold hardy in the group include Newport® (-20 to -30°F), ‘Popcorn’ (-23°F), ‘Fireworks’ (-23°F), ‘Igloo’ (-20 to -30°F), ‘Shasta’ (-20 to -30°F), and ‘Shoshoni’ (-20 to -30°F).

• Viburnum ‘Eskimo’—evergreen in Zone 7, more useful for breeding than I had considered.

• Viburnum ‘Nantucket’ (USNA  69852, f. keteleeri × ‘Eskimo’)—evergreen in Zone 7 with consistent, prolific flower production.

Fruit

• Viburnum betulifolium—brilliant cranberry red, persistent fruit, large shrub.

• Viburnum dentatum—blue fruits are great bird magnets; serviceable, functional shrub with over 20 cultivars; those tested in Georgia were inferior to V. bracteatum ‘Emerald Luster’ with thickish lustrous dark green leaves, self-fertile blue fruits and high heat tolerance.

• Viburnum corymbiflorum (a.k.a. Camellia Forest Nursery)—amber, coral to red, abundant, long-persistent fruit; excellent heat tolerance in Georgia trials. Lustrous dark green leaves, yellow-orange-red fall color.

• Viburnum dilatatum—Cardinal Candy™, red-fruited, listed as hardy to -30°F; yellow types; ‘Michael Dodge’, ‘Vernon Morris’ with beautiful  bright yellow fruit.

• Viburnum nudum ‘Pink Beauty’—prodigious fruit production, compact habit.

• Viburnum setigerum—leggy growth, but a bountiful red fruiting species.

• Viburnum wrightii—often confused with V. dilatatum, red fruit and often red-purple fall color; ‘Hessei’ is more compact. Glabrous stems and inflorescences; pubescent on V. dilatatum.

Small Trees, Large Shrubs: All 10 to 20’ and larger

• Viburnum lentago—native, cold hardy, pretty pink to bluish black fruit, purplish red fall color, mildew susceptible.

• Viburnum macrocephalum—Softball size green to white inflorescences in spring and repeat in fall, heat tolerant.

• Viburnum prunifolium—Stiff, rigid, hawthorn-like habit, pink, rose to bluish black fruits.

• Viburnum sieboldii—Lemon fragrant flowers, rose-red to red to black fruits, large pleated dark green leaves, best in North. ‘Ironclad’ from Roy Klehm considered one of the hardiest.

Foliage: Variegated

• Viburnum dentatum ‘Golden Arrow’—yellow leaf, fades in heat

• Viburnum dilatatum ‘Ogon’—yellow to gold leaf, color fades in heat

• Viburnum rafinesqueanum ‘Louise’s Sunbeam’—three yellow leaf seedlings found in wild in Chapel Hill, NC; Bailey Nurseries, St. Paul, will commercialize the best with lustrous bright yellow foliage and red-purple fall color; species native from Canada to Georgia

• Yellow-leaf forms of V. lantana and V. opulus are occasionally encountered.

Breeding continues at Plant Introductions, Inc. with hope that the nursery industry will embrace the new offerings. To date, acceptance of our selections has been painfully slow. A  grower who supplies the major mega-stores cited reblooming as an essential trait. Where does one go to find those genes beyond ‘Summer Snowflake’?

The new Pearlific™ (‘Nantucket’-02-06), licensed to McCorkle Nursery, is 5’ by 7’ after 6 years, evergreen, with abundant slightly fragrant flowers in early April, and red to black fruit. Easy to propagate, grows vigorously and sets flower buds as a one-gallon container plant. I have noticed that most hybrids with a measure of V. utile genes in the makeup embody the traits mentioned.

For additional information visit my Manual (2009), Viburnums for American Gardens (2007) with 420 photographs, and Lloyd Kenyon’s, Viburnum (2001).