“Which colorful plant can I use in dry shade?” and “What can I plant that deer won’t eat?” are among the gardening questions most frequently asked by visitors to Mt. Cuba Center. For Research Horticulturist George Coombs, coming up with the right answers is what his work is all about.
Coombs runs the Trial Garden at Mt. Cuba Center, where he studies varieties of native plants to determine which are the hardiest, most disease resistant and the most popular in the mid-Atlantic.
For the last three years, Coombs has conducted an exhaustive study of Heuchera, commonly known as coral bells or alum root, to determine which selections of the plant would do best in local gardens. His findings, released this January in a report titled “Heuchera for the Mid-Atlantic Region,” are a valuable resource for area gardeners, landscape professionals and retail nursery owners.
Years ago, Heuchera was known for its green scalloped leaves and stalks of tiny reddish-pink bell-shaped flowers. They were popular with gardeners for their pretty display, but were represented in garden centers by just a few selections.
In the 1980’s, North Carolina nursery owner Nancy Goodwin found a naturally hybridized seedling in her garden that had dark leaves with silver markings. With this discovery, plant growers realized that they could breed new selections for other foliage colors leading to an explosion of a vast array of Heuchera, grown more for their foliage than for their showy blooms.
Fast forward to 2011, when Mt. Cuba Center was looking for plant trial nominees for their upcoming research project. Plant breeders had been busy growing new Heuchera strains with brightly contrasting foliage, but were meeting with inconsistent results. Many of the plants succumbed to disease and were not as hardy as gardeners would have liked. “We decided to study Heuchera because there were so many cultivars available, but we had heard complaints that many of the selections look alike and that some of them wither and die,” Coombs explains. “We wanted to find out which ones were best for our area.”
For the next three years, Coombs made meticulous observations about the 83 Heuchera plants growing in the Trial Garden at Mt. Cuba Center. He measured growth, kept data on bloom time and observed how the plants fared over successive winters. He took thousands of photos, documenting the foliage and bloom color. Each time a plant succumbed to a disease, Coombs and an assistant carefully noted and catalogued the problem and the consequence.
Coombs was also eager to get input about the plants from the local community. At the outset of the Heuchera study, he launched a program to ask visitors to vote for their favorite selections. Mt. Cuba Center is the first research facility to publish this information and give it the attention it deserves. The opinions gathered in the Trial Garden are valuable to the nursery industry, which uses such data to make decisions about what to order for the coming gardening season.
When the research was concluded, Coombs identified the top performers, and confirmed that Heuchera is an ideal addition to the mid-Atlantic shade garden. Coombs also learned some things that he didn’t expect. For example, the study revealed that many of the selections change foliage colors as the leaves mature. He found that a number still provided a lovely display of blooms, especially when planted in large groups. Coombs learned that wet conditions proved to be the biggest disease-causing factor; plants grown in well-drained soil thrived and required less care.
In this region of the country, shaded beds are typically populated with green pachysandra and hosta, which are susceptible to deer damage. Gardeners have long known that deer usually leave Heuchera alone. “No one really knows why, but deer just don’t seem to care for it,” Coombs explains.
“Heuchera are easy to grow and adaptable, living in what can sometimes be difficult conditions. With colorful foliage and evergreen qualities, you get a lot of bang for your buck. The fact that deer don’t like them is an added benefit.”
Mt. Cuba Center’s report has been made available to plant growers, landscape professionals and retail nursery owners to help them make decisions about what to promote in the coming year. “The report helps horticulture professionals offer plants that are popular with their customers and that will be successful additions to their gardens,” Coombs says, adding that it is also a good resource for home gardeners. “The report can help homeowners choose plants that they are confident will grow well in their garden conditions,” he explains.
Now that Coombs has concluded his work on Heuchera, he has begun a new research project on Phlox and continues three-year studies on Baptisia and Monarda. Like the Heuchera study, these research projects are helping Mt. Cuba Center provide fact-based advice about great native plants and how they can be used in backyard gardens.
Great Selections for Delaware’s Shady Gardens
- Heuchera ‘Citronelle’
- Heuchera ‘Cajun Fire’
- Heuchera villosa ‘Bronze Wave’
- Heuchera ‘Color Dream’
- Heuchera ‘Steel City’
- Heuchera ‘Spellbound’
- Heuchera ‘Citronelle’
- Heuchera ‘Southern Comfort’
- Heuchera ‘Guardian Angel’
- Heuchera ‘Green Spice’