Breeding a Better Spiraea

When evaluating a plant species, its cultivars and its future potential, I like to start by growing all the available cultivars in our test garden. This gives me a better understanding of the strengths and weakness of a species and each cultivar. It helps me to know how a new plant stacks up and if it has potential for release. It also helps us identify breeding opportunities.

After growing and evaluating every possible cultivar of Spiraea japonica, we came to the conclusion that there was an opportunity for plants with new and better flower color, better foliage color, improved mildew resistance and better branching. Feedback from our growers indicated they wanted more impulse appeal, mildew resistance, burn resistant foliage, more flowers. Lastly they wanted plants that required less care in production and in the landscape. With this information in hand we started breeding Spiraea.

After six years of breeding Spiraea and three more years of evaluation, we were able to narrow 1,500 potential field seedlings down to twelve candidates. We then propagated and grew on these twelve selections and evaluated them in production as one gallon and three gallons. Plants were also placed in our test garden and again compared to what was on the market. Additionally test plants were sent to key growers across the US to get their feedback. The most difficult part of the process is narrowing the selection down to one or two potential introductions. A cool wet spring made our task a lot easier. It was the perfect spring for powdery mildew. If a plant was going to get mildew, this was the spring. Mildew eliminated about half of the selections left in program.

By August two plants rose to the top as clear winners and were chosen for introduction under a series name call Double Play™. The name Double Play™ was chosen because each plant delivered two or more improved traits; primarily improved foliage and improved flower color. The first introduction is called Double Play™ Artist. This plant was a clear winner early in our field trials because it was compact, had attractive foliage coloration and unusual purple flowers. The foliage is unique because the new growth is a vibrant purplish-red color. As the season progresses the leaves mature to an attractive bluish-green color. The flowers also caught our attention. The flower color is a unique shade of rich purple that we’ve never seen before.

Double Play™ Gold is a dwarf gold leaf selection. It stood out from the other seedlings because it had no mildew, tight branching and a tidy dwarf habit, eye catching pure pink flowers and the plant did not burn when grown in full sun. This plant also stood out in our container trials, as each plant produced was a perfect little soldier with very little pruning.

Growers will begin producing the Double Play™ series next spring and I expect that will be at retail in Spring of 2010.