By Michael A. Dirr, Ph.D.

Little-known, little-grown, little-appreciated, and with limited ornamental assets, Viburnum rafinesqueanum, Rafinesque viburnum, is a sleeper among the 150 or so viburnum species. Twenty-five years past, a rather pretty specimen prospered in the University’s Botanical Garden. I urged Mark Griffith, Griffith Propagation Nursery, Watkinsville, GA, to root cuttings. This he did and the resultant sales were incrementally north of zero.

So, the reader opines . . . why travel further with this discussion? I believe, with selection, the species has a niche, particularly because of its sun, shade, and cultural tolerances. Our time in Chapel Hill, NC, 1999 to 2008, was the open window that introduced me to the species. Virtually everywhere in the wild, typically as an understory and woods-edge plant, often dominant. Seedlings, bird-planted, were common in our Chapel Hill garden. The species prospers in near neutral soils and I noticed stress in dry years but plants were back to "normal" the following year. Trees and Shrubs for Northern Great Plains Landscapes (NDSU, 2007) noted the species was similar to V. dentatum, but better adapted and more stress-tolerant in the Great Plains. Paul Jones, curator, Sarah P. Duke Gardens, Durham, NC, has an affinity for the species and allowed it to self-seed in areas of the garden.

The extensive native range from Quebec to Manitoba to North Carolina, Georgia, Kentucky, Missouri, and Arkansas, where it occurs in calcareous soils of dry slopes and woods, speaks to its adaptability. Habit is significantly variable from finely-twiggy, relatively compact rounded to loose, open, and upright. Size ranges from 5 to 6' high, 6 to 8' wide to 10' and more upright. At the Minnesota Landscape Arboretum (MLA), Chaska, several tightly-knit, dome-shaped (see photo) plants were evident.

Foliage, typically dull dark green, 1 to 2 ½" long, 1 to 1 ¾" wide, emerges early in spring, mid-April in Chapel Hill, becoming muted red to russet red in autumn. I was perpetually on the lookout for a bright red selection, but to date with no good fortune. Leaves are coarsely toothed with 4 to 6 prominent veins and can be mistaken for those of V. dentatum. Within native populations of V. rafinesqueanum resides V. dentatum. The latter has larger, more lustrous, uniformly serrate leaves with 6 to 10 vein pairs and flowers 10 to 14 days later.

Flowers open early April with early May umbrellaing the late arrivals in zone 7. The white, malodorous flowers are held in 1 ½ to 3" wide, 5- to 7-rayed terminal cymes. Sun-sited plants are more floriferous than those in shade, although floral production is among the highest for shade-grown viburnum species.

The 1/3" long, ellipsoidal, shiny black fruits ripen by July and are quickly taken by the birds. Noticed some fruits transitioning from red to black. Fruits do not overwhelm and are, to a degree, camouflaged by the foliage.

The only malady observed (07-20-2005) was mildew which occurred on several plants at the MLA. Have yet to note insect damage, although suspect the viburnum beetle may be an issue in the North. Listed as highly susceptible by Paul Weston, Cornell University.

Thrives in calcareous soils, as well as acid as long as well drained. Adaptable from zone (3)4 to 7. I have transplanted seedlings in full leaf from the wild with success. Has been easy to propagate from firm-wooded cuttings. 'Louise's Sunbeam' rooted 85 to 90% with 06-25-10 cuttings treated with 3,000ppm KIBA and overwintered without loss.

I suspect that most readers, at this juncture, are still not enthralled with the species. Is it something that has a place (read: spot) in the garden? If nursery producers grow numbers, will it sell? The answers are no and no but . . . let's continue the journey. In early May 2005, Bonnie, Susy, Madeleine Quinlan and I were driving to a service for Susy's donor Mom. Susy was blessed to receive Madeleine's daughter, Louise's lungs. This vivid yellow leaf shrub was growing at the woodland edge and I thought it might be a V. rafinesqueanum variant. Not a time to stop said Bonnie, so a few days later I returned to verify. Indeed, a miracle and I christened this initial discovery 'Louise's Sunbeam'. Waited until fall, dug the plant, containerized and anxiously awaited spring regrowth and potential cuttings. Reflected on whether other yellow-seedlings might have occurred since the original, 4' by 4' plant, flowered and fruited. In mid-April 2006, I discovered two additional seedlings, the smallest about 6" high with stunning sheeny pure yellow leaves. This little seedling, after 5-years evaluation, proved the best of the three and will be introduced as 'Louise's Sunbeam'. This plant, in the new Dirr garden, is 35" high and 28" wide. Leaves emerge bronze-red then illumination yellow, yellow-green in the heat of Georgia summer, and bronze-red in autumn. For color in a shady border, woodland understory plantings and massed for explosiveness, 'Louise's Sunbeam' is magnificent.

'Louise's Sunbeam' will be introduced through Plant Introductions, Inc. and Bailey Nurseries, St. Paul, MN. Royalties will be shared with the Sweet Melissa Foundation at the University of North Carolina, Chapel Hill, to support transplant patients and their families.

Why did this plant appear on the Dirr radar during the drive to the service? I have no absolute answer, but believe that miracles do occur whether accepted as such or not. 'Louise's Sunbeam' is one of those.