A second look

What’s new in viburnums? Actually, no one ever asks this question. It’s a genus with great functionality, but insufficient “wow” factor to arouse the average gardener. Even nursery producers are jaded, particularly in the Southeast, where proclamations of, “They don’t sell” outdistance their inherent good. I queried the president of a large southeastern nursery about the merits of several University of Georgia/Plant Introductions Inc. selections and his first words were, “Do they rebloom?” He added a reblooming fragrant type like V. carlesii would be a huge seller. Note the emphasis on the word “seller.” More than ever in my 40-plus-year career, I am convinced that there are “seller” plants and “collector” plants.

Where are the genes for reblooming in viburnum? Viburnum plicatum f. tomentosum ‘Summer Snowflakes’ is a good rebloomer. Viburnum obovatum, small viburnum, spits white flowers from fall to spring. Viburnum macrocephalum, Chinese snowball, spring and fall, but is sterile. The V. × bodnantense, V. foetens, V. fragrans and V. grandiflorum taxa flower sporadically from fall into early spring. None, except ‘Summer Snowflakes’ qualifies for “seller status.” The nursery president wanted a fragrant, semi-snowball type with potent reblooming genes. If any reader knows of such a genetic miracle, then head straight to the patent office.
 

A case for viburnum

What to do? Appreciate the magnificence of the genus for the sum of the parts: flower, fragrance, fruit, fall color, evergreen, deciduous, large, small, nativity in U.S., adaptability from Zones 3 to 9, with form and function for every landscape dilemma/challenge.

Since 2000, a significant number of viburnums have been introduced with only seven patented (uspto.gov) (see Table 1). Hydrangeas, for comparison, in the same time period, number in the hundreds. It’s worth mentioning that plant patents are valid for 20 years from date of application. The inventor/assignee controls licensing, sales and royalty schedules. No other party may propagate, license, offer for sale, etc., except the owner. Note that trademarks are a totally different story. Trademarks represent only the marketing name attached to the plant. Without patent protection, the trademark name is almost worthless, for anyone can name the plant and offer for sale under a new name, trademarked or otherwise. The point of this discussion is that most viburnums have only trademark names.

My attempts to connect with all viburnum introductions are fallible, albeit not intentionally. If readers know of others, please advise. At The University of Georgia and Plant Introductions, Inc. open-pollinated and controlled cross hybrids were constituted. To date, only Pearlific has been introduced. Selections are still under evaluation that range from 7 to 12 years old. The viburnum process is slow. A current example relates to seed collection from open-pollinated ‘Susy,’ a floriferous, lustrous dark green, white-flowered, red to black fruited selection from ‘Eskimo’ in 2003.

Original plant is 7’ by 6.4’ after 10 years. Has resolutely withstood the heat and drought of 2011 and 2012 without supplemental irrigation. Rooted cuttings develop copious flower buds the first season. Obviously, ‘Susy’ has excellent genes so we continue to explore the possibilities for newer selections. Seeds of ‘Susy’ were collected 10-17-11, cleaned and placed in warm stratification 10-27-11, then to cold 1-27-12, sown in flats 4-27-12, with germination (sporadic) 11-3-12. The seedlings were transplanted to cells in early 2013, then into 3-gallon containers in summer 2013, then grown for two to three years until flowering (fragrance, size, abundance) can be assessed. Then to the field and another three to five years to target the best.
 

Keep searching

Most (all) recent commercial introductions resulted from row-run seedling populations. Minimal focused, structured breeding is being (has been) conducted.

‘Nantucket’ (NA 69852, PI 651840) is a beautiful evergreen, slightly fragrant, white-flowered, red- to black-fruited hybrid of ‘Eskimo’ × V. macrocephalum f. keteleeri. ‘Eskimo’, itself, was derived from open-pollinated seed from the cross [(V. carlesii × V. ×carlcephalum) × V. utile]. The controlled cross was made in 1988 by the late Dr. Donald Egolf and the plant released in 2008, an amazing 20 years in process. Original plant was 12’ by 7’ in 16 years. Has been in the Georgia trials for 12 years and is 8’ by 8.4’. Abundant slightly fragrant flowers every year, completely evergreen, heat and drought tolerant, this is an outstanding Zone 6 to 8 option. Easy to root and sets prodigious flower buds as a young plant. Where is it in commerce?

When I noticed fruit on ‘Nantucket’ my eyes morphed into saucers. Wow! With the complex and varied parentage, what might be spawned in a seedling population? Out of 22 seedlings, planted in 2006 at the Horticulture Farm, all but two were similar to V. macrocephalum f. keteleeri with lacecap flowers and red to black fruit. Two, originally designated 69852-01-06 and -02-06, semi-evergreen to evergreen, respectively, showed promise. All the f. keteleeri types were rogued with the above two, now, 5’ by 5.5’ and 5’ by 7.9’, 7-years-old, extant and worthy potential introductions. 69852-02-06 is now Pearlific (‘PII1B-1’) PPAF and licensed to McCorkle Nursery, Dearing, Ga. Evergreen, rounded shrub, pleasantly fragrant white flowers in 3-5” diameter convex cymes in early April, red to black fruits, roots readily, set abundant flower buds, excellent vigor in a container, insect resistant, heat and drought tolerant. The original plant has received no supplemental irrigation for the last four years. The positive attributes of V. utile are readily evident in this hybrid. I envision this as an alternative to ‘Conoy’ because of stronger constitution and ease of container culture. The early onset of copious flower buds on young plants is truly exceptional.

69852-01-06 did not garner enthusiasm from visitors. Why? I do not know. In flower, the 4 -5” diameter inflorescences remind of a ‘White Wave’ lacecap hydrangea and literally smoother the foliage in mid-April (Athens). The 2-5” long lustrous leathery dark green leaves turn wine-red in late fall-winter. More compact than Pearlific and has yet to fruit to any degree. Currently being evaluated for introduction by Plant Introductions, Inc.

Might mention that seedling populations derived from V. × burkwoodii, V. ×burkwoodii ‘Park Farm Hybrid’ × V. macrocephalum f. keteleeri, V. × carlcephalum ‘Cayuga’, V. corymbiflorum, V. nudum ‘Pink Beauty’ yielded little of worth. Considering the hundreds (probably now thousands) of viburnum seedlings pitched, one might question the wisdom of continuing to breed. Will . . . from ‘Eskimo’ came ‘Susy’, ‘Mowhawk’ spawned 11-03, a dense rounded, large shiny dark green leaf form with red-purple fall color, gleaming red buds, white flower, explosively fragrant, now 6.5’ by 8’ in 10 years.

The rarest viburnum I worked with is V. corymbiflorum. Of the two original seedlings purchased from Camellia Forest Nursery, Chapel Hill, N.C., one produces yellow to coral to red fruit in a 4 to 6 week span starting in late September into early November (Athens). Fruits persist into winter. This most beautiful fruiting specimen has a miserable habit and hundreds of seedlings later, there is no improvement. With quality habit tied to the fruiting traits, the result will constitute a beautiful garden shrub. Might add that foliage is lustrous dark green and turns yellow-orange-red in autumn.
 

To afford a concept of the species size, the sister seedling was 9.2’ by 11.5’ in 10 years with green to red fruits. Yellow-red foliage still present on November 6, 2012 when size measurements were taken.

Kevin Spellman, via email, sent me photos of an upright (fastigiate) V. plicatum f. plicatum bird-planted seedling in his Illinois garden. Information was exchanged as well as cuttings and seeds [yes, from a sterile(?) snowball type]. ‘Popcorn’ from David Leach is a Dirr favorite Japanese snowball, but Kevin’s is more upright, with decidedly larger, thicker, heat-tolerant leaves. Fall color has ranged from maroon to red. Easy to root and a strong, vigorous grower in a container. Typical white snowball flowers are produced in quantity along the upright stems. Gary Ladman, Classic Viburnums, is producing the plant. Three seedlings resulted, with one selected for its smaller leaves, red fall color and upright habit. Yet to flower, so the jury is still out on absolute worthiness. To date, excellent heat tolerance at PII, but based on early signals will pale alongside Kevin’s original.

An exciting aspect of any breeding program is the development of new breeding lines, nowhere else available in the Universe. Dr. Josh Kardos, breeder at PII, integrated Pearlific (69852-02-06) and Mohawk-11-03, the resulting seedlings absolutely beautiful in foliage with flower buds visible in 2012 (see photo). He also crossed V. bitchiuense × Mohawk-12-03, the latter the latest flowering fragrant semi-snowball type I have observed. These latter hybrids are rich with flower buds. All the above 3 to 4 years old and 2013 will tell the story of their floral worth. Hope springs eternal in plant breeding. Truly, there is more to viburnums than is currently available at the garden centers.

Michael A. Dirr is founder of Plant Introductions Inc.; www.plantintroductions.com and retired professor of horticulture at the University of Georgia.