Plant discovery

Richard Olsen, a research geneticist at the United States National Arboretum, and I have often discussed plant breeding with defined objectives and the potential for achieving certain goals.

A case study might focus on the discovery of a new Ulmus parvifolia (lacebark elm) with maximum height and width of 15-25 feet, 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 and assemble all extant germplasm of U. parvifolia, perhaps concentrating on dwarf, compact types like ‘Catlin,’ ‘Chessins,’ ‘Ed Wood,’ ‘Hokkaido,’ ‘Stone’s Dwarf’ and others. Attain the major shade tree cultivars that offer superior genetics, outplant them all and evaluate them 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.

Next, collect seed, germinate, maintain seedlings, outplant and evaluate them for the desired original traits for another five to 10 years. It 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 —there’s vegetative propagation, testing for trueness-to-type, sharing with nurseries, patenting, trademarking and marketing. Does the process ever end?

Neighborhood discovery
How about allowing serendipity, the powers of observation and blind good fortune to substitute for most of the above steps? The compact lacebark elm was targeted as the example because I discovered such a tree in my daughter Katie’s Athens, Ga., 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 and in streetscapes.

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.

I believe I could do everything outlined above in controlled breeding and not succeed to the degree of this drive-by sighting.

I wonder, how many people walked and drove by the tree without really seeing its unique characteristics?
Persistence, scientific breeding and serendipity will continue to result in new and worthy plant introductions. Allow me to share several Dirr family serendipitous discoveries.

An outing with mom
Hydrangea quercifolia ‘Amethyst’ features red sepals.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 a large seedling planting in town. Zipping here and 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. I acquired cuttings—a few with the ruby-red sepals still aglow. I took them to Georgia where my wife Bonnie decreed it ‘Amethyst,’ rooted it and gave it to anyone who would take it. Growers still tell me it is one of the easiest to produce in a container. ‘Ruby Slippers,’ a selection from the National Arboretum’s Sandy Reed, appears promising with rose-red sepals —a result of 12 years of breeding and evaluation. ‘Amethyst’ resulted from an afternoon drive with mom and at no expense to the taxpayer.

A stroll in the arboretum
My longest, commercially persistent introduction is Fothergilla ‘Mt. Airy,’ now with more than 30 years of garden acceptance. I observed it in the early 1970s at the Mt. Airy Arboretum in Cincinnati, with larger flowers, beautiful blue-green summer foliage and reliable yellow, orange and red fall color. Tom Ranney, professor at North Carolina State University, 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. gardenia, found in moist to wet soils in the Coastal Plains and F. major in well-drained soils in the mountains. Nursery growers have labeled ‘Mt. Airy’ as a relatively easy plant for production. Many introductions have challenged ‘Mt. Airy,’ but a perusal of nationwide nursery catalogs reflects its staying power.

Bonnie’s observations
With sweet Bonnie on continual plant alert when we are driving, she spotted a rich pink redbud, Cercis canadensis, at Exit 2 on Interstate 85 in North Carolina. Quite an impressive sighting at 70 mph. Scionwood was collected the next winter and sent to J. Frank Schmidt & Son in Boring, Ore. The first plant was 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.

The back roads
During a March 2007 trip exploring the Shenandoah Valley of Virginia, we saw 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 had ever experienced.

I asked for scionwood and sent it to J. Frank Schmidt & Son, and in 2009, I had two-year-old grafted trees. Wow! Frank Schmidt III and Keith Warren, director of product development, 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. It should be available from Schmidt in 2012. Serendipity wins again, and Bonnie brings a better set of eyes to the table than mine. The journey continues.

The road to Charlottesville
It’s a misty, cold, cloudy, early-February day—another 500-mile drive to Charlottesville, Va., for lectures. Bonnie and I decide to detour and visit a parcel of land we own in Pipers Gap, Va. Returning to the interstate, a red light appears, only in the form of a shrubby dogwood growing in a swampy habitat. “Bonnie, did you see that?” And the car jumps the median. I go 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. Cuttings were requested from a local beaver who dammed this swamp, granted, and were successfully 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.

Perhaps another time
The one that got away may be the best plant story. Returning from our son’s June graduation at Georgia Southern University in 1998, with 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. Dressed up in a coat, tie and respectable shoes, I’m out of the car, heading for deep water, 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.

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