The Roll of Serendipity in Plant Discovery and Introduction

By Michael A. Dirr, Ph.D.

Dr. Richard Olsen, U.S. National Arboretum, and I have discussed plant breeding with defined objectives and the potential for achieving the goals. A case study might focus on an Ulmus parvifolia, lacebark elm, with maximum height and width of 15 to 25', compact habit, disease-free dark green foliage, and exfoliating bark. What are the prerequisites for initiating the breeding process? Digest the literature on elm breeding, assemble all extant germplasm of U. parvifolia, perhaps concentrating on dwarf, compact types like 'Catlin', 'Chessins', 'Ed Wood', 'Hokkaido', 'Stone's Dwarf', and others. Accession the major shade tree cultivars that offer superior genetics. Outplanting all and evaluating for superior traits over a five year period. Now it's time to make controlled crosses, probably reciprocally to assess maternal and paternal inheritance patterns. Collect seed, germinate, maintain seedlings, outplant and over 5 to 10 years evaluate them for the desired original traits. Might prove necessary to backcross to original parents or grow F2 populations for segregating characteristics. Let’s assume the perfect tree is identified. Is this the end? Absolutely not, for vegetative propagation, testing for trueness-to-type, sharing with nurseries for increase, patenting, trademarking, marketing . . . does the process ever end?

 

Or allowing serendipity, powers of observation, and blind good fortune to substitute for most of the above. The compact lacebark elm was targeted as the example because I discovered such a tree in my daughter Katie's pervious Athens neighborhood. Remarkably, the builder planted seedling Ulmus parvifolia, Acer buergerianum (trident maple), and Acer saccharum (sugar maple). I named this potential introduction 'Small Frye' and believe it has potential under utility lines, smaller residences, street-scapes. I estimate the neighborhood is about 20 years old and most of the trees are of similar vintage. Every characteristic previously enumerated is embodied in this restrained biological beauty.

 

My question . . . how many people walked and drove by the tree without really sensing ("seeing") the uniqueness? The answer resides in observation, the "feel" for a particular species' genetic plasticity (variation), predicting what the tree market could utilize. Innately, I believe I could do everything outlined above in controlled breeding and not succeed to the degree of this drive by sighting.

Ulmus parvifolia 'Small Frye'

Persistence, scientific breeding, serendipity will continue to result in new worthy plant introductions. Allow me to share with the reader the plants and stories attached to several Dirr serendipitous discoveries.

 

My sweet Mom, then 88, and I were taking a scenic drive in my hometown of Cincinnati. I mentioned to Mom that many years past, a "red" flowered form of Hydrangea quercifolia (oakleaf hydrangea), occurred in large seedling planting. Zipping here, there, and at times lost, with the White Castle coffees sloshing out of our cups, Mom shouted: Is that IT?! No doubt about the authenticity of the sighting. Cuttings were acquired, a few with the ruby-red sepals still aglow, taken to Georgia where Bonnie decreed it 'Amethyst', rooted, and given to any who would take. Growers still tell me it is one of the easiest to produce in a container. Dr. Sandy Reed's U.S.N.A. 'Ruby Slippers' appears promising with rose-red sepals and resulted after 12 years of breeding and evaluation. 'Amethyst' resulted from an afternoon drive with Mom and at no expense to the taxpayer.

Hydrangea quercifolia 'Amethyst'
The longest commercially persistent introduction from the author is 'Mt. Airy' Fothergilla, now with over 30 years of garden acceptance. Observed in the early 1970's in Mt. Airy Arboretum, Cincinnati, Ohio, with larger flowers, beautiful blue-green summer foliage, and reliable yellow, orange, red fall color. Requested cuttings, granted, rooted, and given to all who visited. Dr. Tom Ranney, NCSU, determined 'Mt. Airy' is a hybrid of F. gardenii × F. major, with the species moniker F. ×intermedia. Initially, I aligned 'Mt. Airy' with F. major. Perhaps, its great cultural adaptability equates with the hybrid parentage, F. gardenii found in moist to wet soils in the Coastal Plain; F. major in well drained soils in the Piedmont and mountains. 'Mt. Airy' has been labeled a nursery grower’s plant for production is relatively easy. Many introductions that have challenged 'Mt. Airy', but a perusal of nationwide nursery catalogs reflects its staying power.
Fothergilla xintermedia 'Mt. Airy' flower
Fothergilla xintermedia 'Mt. Airy' fall color
With sweet Bonnie on continual plant alert when we are driving, she spotted a rich pink redbud, Cercis canadensis, at Exit 2, I-85 in North Carolina. Quite an impressive sighting at 70mph. Scionwood was collected the next winter, sent to J. Frank Schmidt & Son, Boring, OR, with the first plant ensconced in the Dirr garden in 2009. True-to-type, rich vibrant neon pink, vigorous and named 'Bonnie's Pink', it is the tie that binds and offers memories never to be forgotten. Commercial? Perhaps not. Personal? Absolutely!

Cercis canadensis 'Bonnie's Pink'
A March 2007 trip exploring the Shenandoah Valley of Virginia, the drive from Chapel Hill, NC, to Fancy Gap, VA, then every backroad to Winchester, Charlottesville, and home. Then it appeared: an upright, tightly fastigiate oak that had me examining buds and hunting acorns. Quercus bicolor, swamp white oak, was the answer, but like none I have ever experienced. Asked for scionwood, granted, sent to Schmidt’s, and in 2009, two-year-old grafted trees met my eyes. Wow! Frank Schmidt, Jr. and Keith Warren, horticulturist, were both impressed. So the Bonnie and Mike oak will experience the dawn of a commercial day. The emerging shiny bronze-green leaves mature lustrous dark green on a soldier-at-attention framework. Keith has compared it to the various hybrid Q. robur 'Fastigiata' × Q. bicolor hybrids and decreed it different. Should be available from Schmidt's in 2012. Serendipity wins again and Bonnie brings a better set of eyes to the table than mine. The journey continues.
Quercus bicolor BeaconTM ('Bonnie and Mike')
Misty, cold, cloudy, early-February day . . . another drive, 500 miles to Charlottesville, VA, for lectures. Bonnie and I decide to detour and visit a parcel of land we own in Pipers Gap, VA, near the Blue Ridge Parkway. Returning to the Interstate, a red light appears, only in the form of a shrubby dogwood, growing in swampy habitat. Bonnie, did you see that? See what? Car jumps the median. Back to make sure my visual senses were true to color. Indeed, a red-stemmed Cornus amomum, silky dogwood, brown pith the absolute arbiter compared to the white pith of C. sericea, redosier dogwood. In the South, it is impossible to culture C. sericea for any length of time because of heat and canker. However, C. amomum ranges from Massachusetts to Georgia, grows locally in wet, swampy habitats, and is common around Athens. The stems are reddish purple, sometimes green, older stems brownish purple, largest gray. Cuttings were requested from a local beaver who dammed this swamp, granted, and have successfully been rooted. I look forward to continued testing and hope this red is as true as what the original plant offered.

 

In the Manual of Woody Landscape Plants 2009 edition I opined "I see the species everywhere in the eastern United States, almost always along streams. Have searched for unique forms with improved stem color, smaller habit, abundant colorful fruits. A large seedling population grows along Crooked Creek in Virginia and I could not find a penny’s worth of differentiation in the seedlings. One of these days!" The day came! Persistence and serendipity may have delivered dividends. This plant will be introduced through Plant Introductions, Inc.

Cornus amomum, typical winter stem color
Cornus amomum, Dirr's new red-stemmed find!
The one that got away may be the best plant story. Returning from our son's June graduation at Georgia Southern University in 1998, Bonnie and her Mom and Dad chatting-away, I spy large white golf-ball size eyes on a compact shrub peering at me from the black swampy water. Finally, the Holy Grail of shrubs, a compact, large, and I mean enormous, flowered Cephalanthus occidentalis (buttonbush). Another species on my radar that needs selection to become mainstream. Coat, tie, respectable shoes, out-of-the-car, heading for deep water, and water moccasins, and the PLANT. A voice, Bonnie, in resonant tones, Michael, back in the car. You're crazy! This is the end. Mom and Dad always wondered about you. Now they know. I paused, pondered, reflected, debated, and failed to collect. Another time, I'll return for the ONE that got away.
Cephalanthus occidentalis, the one that got away