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Taming the Wild Plant

^ JD Walker &

Inlate spring 2022, I was enjoying a bit of agritourism while on a short road trip. For those unfamiliar with the term, agritourism combines the working of a farm or other agricultural business with recreational activities open to the general public. In this case, I was at a small suburban garden center that also included a petting zoo, duck pond, craft beer and snacks area, and small music venue. While browsing the center’s plant collection, I came across an old friend from the plant kingdom.

“Well, look at that,” I thought to myself. “Someone has tamed the wild cow-itch vine.”

People in the southern United States need no explanation of what a cow-itch or trumpet creeper vine is. Botanically speaking, it is Campsis radicans, a deciduous, wildly aggressive vining plant that will attach to anything that stands still long enough. The leaves can cause contact dermatitis in some people. Given the opportunity, the vine will grow thirty feet long with a lateral spread of four to ten feet. Pulling it up is not an option. It has a death grip on any land, post, barn, or house it grows in or around. Its saving grace is gorgeous, red-orange or yellow trumpet-shaped flowers that hummingbirds adore.

I have often thought when seeing it come into bloom around July along cornfields and road ditches that it would make a lovely garden specimen if you could reduce the height . . . and subdue its aggressiveness . . . and do something about the millions of seeds it produces . . . and maybe fix that mildly toxic dermatitis it causes. Basically, what any gardener would want is the lovely flowers without the overall boorishness of the plant.

Why Breed New Plants for the Garden?

The drive to find new introductions for the landscape is a major reason why researchers keep breeding or hybridizing new plants. In her 2008 book Flower Confidential, author Amy Stewart points out breeders are often looking for larger flowers, new colors, bigger (or smaller) versions of plants, and greater durability. In the case of cow-itch vine, it turns out people have been working on this North American native almost since Europeans first landed on the new continent. English botanist John Parkinson described the plant in his Paradisi in Sole, first published in 1629. From there, it spread in popularity to the rest of Europe. C. radicans ‘Flamenco’ is an example of a variety of the native vine that was bred in Germany. It helps to understand that in the cooler climates of northern Europe, cow-itch is a bit more restrained in growth.

Aesthetics aside, we are finding out that we need new plants for other reasons. As the climate changes, we may not be able to rely on the old standbys in commercial farming. Plants have to be more heat and drought tolerant. If we hope to cut down on the use of insecticides, we need plants to be more resistant to bug infestations. Of course, a big driver of crop development has always been greater harvests from the same acreage planted.

Going from Concept to Reality

The old-school way to get new plants is to control their sex lives. It sounds dirty, but it’s not. Plants of the same family are selected that have desirable characteristics, such as a unique bloom or particular color or special growing habit. The plants are brought to bloom, often in a greenhouse or contained location. The breeder then carefully takes pollen from one plant flower and dusts it into the bloom of another plant.

This is a slow process that must be done two parent plants at a time. The breeder can’t mix the pollen from multiple plants into one blossom. The bloom is then protected, usually with netting, to keep insects or air movement from introducing additional pollen from another plant. The plant sets seed: those seeds are collected and eventually planted. The new plant is monitored to see if the desired traits—any of the desired traits—are present in the offspring of the original cross.

This has been done with cow-itch vine. Breeders crossed the aggressive North American C. radicans with the more mild-mannered Asian C. grandiflora. The result was the new plant C. ×tagliabuana, a shorter vine with a more open flower that is still more resilient than its Asian parent.

A Labor of Love

When the process works and the breeder is lucky, the new plant delivers that bigger bloom or new color. Unfortunately, it’s rarely that simple. Famed plant breeder Luther Burbank worked for years to develop the Shasta daisy (Leucanthemum ×superbum). This is the flower we immediately think of when someone says “daisy.” It’s a large, white-rayed flower with a bright yellow center, presented on strong stems that are perfect in a cottage garden or in a bouquet. Why did he do it? He just loved daisies.

Burbank started by growing wild ox-eyed daisies (L. vulgare) to get the best and strongest plants possible. Next, he crossed the result with the English field daisy (L. maximum). The result was considered better but not good enough. The new daisy was crossed with the Portuguese field daisy (L. lacustre). This gave Burbank the large flowers he wanted but a less-than-brilliant white color. The next cross was with the Japanese field daisy (Nipponanthemum nipponicum). Burbank ended up with bright white flowers that were smaller than desired. After several seasons of crossbreeding these last new plants with each other, Burbank finally ended up with the Shasta daisy we know today.

This process took seventeen years. But that is a drop in the bucket to the time some plants have undergone hybridization. The forerunners to our summer geraniums (Pelargonium ×hortorum) were first collected by Europeans in the early 1700s from South Africa (P. sidoides). Striking plants in their native environment, these predecessors look distinctly different from our zonal geraniums. The natives grow with red or white flowers. Modern geraniums come in nearly every shade except blue. This is due to busy breeders hard at work in the greenhouse. As is often the case, the South African plants tend to be smaller and more compact than our summer standards.

While humans have been manipulating plants (often accidentally) for thousands of years, Thomas Fairchild of London was the first person to scientifically produce a new plant in 1717 with methods still used today—the Dianthus caryophyllus barbatus, a cross between the sweet william and carnation plants.

Europeans did the same thing with North American deciduous azaleas. In my area of the country, we often think of the flame azalea (Rhododendron calendulaceum) or the Piedmont azalea (R. canescens) when we talk about the wild deciduous azaleas, but there are many natives in this group of plants. In the early 1700s, plant collectors took samples of all these new plants, bred them in English nurseries with the European R. luteum, and sent us back the Ghent, Knapp, and Exbury azaleas we find in garden centers today.

Of course, all this breeding and hybridizing does come with drawbacks. Old World explorers were introduced to maize (Zea mays) in the fifteenth century. At that point, researchers think maize had already been in cultivation for about 6,000 years. The plant the Spanish explorers saw was a tall plant (ten feet and higher) that produced small ears made up of cobs that had few kernels that could be white, yellow, red, purple, and even green. After hundreds of years of more hybridizing and crossbreeding, most of us enjoy Z. mays var. saccharata, or sweet corn, and Z. mays var. everta, or popcorn.

As tasty as they are, these varieties of corn would probably not survive in the wild, researchers tell us. All the domestication has resulted in corn kernels that don’t easily detach from the cob without the help of human hands or hulling machines. The outer leaves or husks tend not to relax as the cob ages. Both traits keep birds and small animals from helping distribute the seeds.

New-School Breeding Techniques

As noted, the old way plants were improved or adapted to modern use can take years, even decades, to produce viable results. Even then, the changes may not be permanent. Anyone who has grown an F1 hybrid tomato knows they get a strong, disease-resistant plant that produces abundantly for a long growing period. However, if they save the seeds in the hopes of growing their own tomato sets next season, the result will likely not be the same.

The reason is that the hybridized plant doesn’t come back “true to seed,” as my grandmother would say. The offspring will tend to resemble one or the other of its parents—usually a smaller plant with smaller, cherry tomatoes. Grandma would buy new tomato sets each year to get tomatoes for sandwiches and for canning. But we never wanted for cherry tomato plants. We just went down to the pig pens around May and dug up any of the many tomato seedlings that sprouted from last year’s wasted tomatoes.

Much discussion has been made of genetically modified organisms or GMOs. This is the process of taking the genes that result in a set of desired characteristics from one plant and inserting those genes into a different plant. Some people worry about the unintended consequences of “Franken-plants.” Could GMO plants crossbreed with existing crops or even wild plants in waste areas around fields to produce a noxious weed that could not be controlled? Could GMO plants do harm to surrounding wildlife or even to humans who consume the plant (or its produce)?

These may be valid concerns, but not for the home gardener—at least not yet. The process to produce GMO plants is very expensive and mostly limited to commercial farming. Currently, the only GMO crops available in the United States are corn, soybeans, papaya, cotton, squash, canola, alfalfa, and sugar beets. These are not available “over the counter,” so to speak, to the average homeowner. European breeders have come up with a handful of carnations and one rose for the flower markets there. However, again, the average homeowner can’t buy GMO carnations or roses.

Growing Forward

Plant hybridizing is a labor-intensive process that requires true attention to day-to-day details. I’ve known several dedicated gardeners who started as avid hobbyists and morphed into plant breeders. It usually starts out as intense devotion to a particular species of plants, be that flower, vegetable, shrub, or tree. The result isn’t always a desirable offspring. Even if the hobbyist does create an outstanding new plant, the chances are someone has already beat them to that particular combination and sent it off for patenting.

Resources

Cash, R. Christian. “Exbury Azaleas—From History to Your Garden.” Temple University. Accessed October 18, 2022. https://scholar .lib.vt.edu/ejournals/JARS/v40n1/v40n1-cash1.htm.

Favretti, Rudy J. “Colonial Gardens.” Arnoldia 31, no. 4 (1971): 145–71. http://www.jstor.org/stable/42962477.

“Shasta Daisy.” Luther Burbank Home & Gardens. Accessed October 18, 2022. http://www.lutherburbank.org/about-us/shasta-daisy.

Stewart, Amy. Flower Confidential. New York: Algonquin Books, 2008.

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