the best heuchera and how to grow them, with mt. cuba center
WHAT SHADE perennial has beautiful foliage in a dramatic color range, attractive flowers, offers multiseason interest with low maintenance, and is also drought tolerant and deer resistant—and inclined to cause indecision and perhaps dizziness if you try to select which variety to buy among the many in catalogs and garden centers?
If you said Heuchera, you’re right. Perhaps you’re going to reshuffle some shady beds this spring, and know that Heuchera, with their great foliage, can help make garden pictures work–but wonder which ones, and how best to use them. I invited George Coombs, trial garden manager at the must-visit Mt. Cuba Center in Delaware, with 50 acres of native-plant display gardens and 500 acres of natural land, back to the radio show to help make the best choices and grow them to perfection.
George knows from Heuchera, having trialed 83 varieties side by side (the exhaustive results are in this pdf). “I say to people, ‘I’m doing Consumer Reports for plants,'” he explains. Though there are countless varieties on the market, many are duplicative in appearance or just not distinctive. “I can honestly say that when it came time to end the trial, there were very few Heuchera that I wanted to take home for my own garden,” George says. But stars there were.
For dramatic groundcover. For growing in pots in shady places. For unifying shade-garden designs.
Listen in now to the April 6, 2015 show, using the player below or from this link, or read along–or both.
my heuchera q&a with george coombs
A. Heuchera have been around for a long time, and were one of the first plants exported back to Europe, in the 1600s, by early American explorers. It wasn’t until recently that people started to think of them as foliage plants.
The common name is coral bells, and that’s a pretty well-known plant, but that’s not really what we’re talking about. Those old-fashioned coral bells were typically ones with red flowers, and plain green foliage—maybe they’re variegated. Those plants are native to the American Southwest, so they weren’t part of our trial at Mt. Cuba, where we’re looking at plants derived from Heuchera americana and Heuchera villosa [below].
A. Yes, there were hybrids as well, but that was the predominant species.
Q. Are all three species you’ve mentioned, then, native to the Americas?
A. There are about 35 species, all native to North America—so it’s a North American genus—which is really cool.
Our trial focused on the Eastern species, which became foliage plants, instead of floral plants, like the sanguineas. There were two forms found in the 80s: a purple-leaf form of Heuchera villosa, which is normally green, and a highly silvered cultivar of Huechera americana. Those two cultivars–Heuchera ‘Dale’s Strain’ and what was essentially Heuchera ‘Palace Purple’—were planted in a garden in North Carolina, a famous garden called Montrose that was a well-known nursery back in the day.
The owner had these two plants growing side by side, and noticed that this unusual seedling had come up between them, and it became known as ‘Montrose Ruby.’ It was interesting because it was the first plant to combine the darker foliage with the silver mottling or veil. That plant was kind of the kickoff of the thought to use Heuchera as foliage plants.
Q. I remember visiting Nancy Goodwin’s garden that you are speaking of, back around that time. It was amazing. She had an eye for foliage—Cyclamen, for instance, and other signature plants. So ‘Montrose Ruby’ was the beginning.
A. Yes, and we include all three of those plants in our trial, just to see the beginnings of Heuchera and how far they have come with breeding.
Q. Speaking of breeding: flowers weren’t the goal with Heuchera, so…
A. …I think people were realizing you get a lot more bang for your buck when you think about plants for their foliage: bright-colored foliage, ruffled foliage, different textures, sizes. So flowers fell by the wayside, and the parents being used to create these new plants didn’t have showy flowers, so there wasn’t much to work with, anyway.
Q. What did H. villosa contribute, versus the species H. americana?
A. Villosa is a more Southern plant, so it imparts tolerance to heat and humidity. It’s a larger plant, with fuzzy leaves that are more angular, and a kind of open architecture. Heuchera americana is more of a mounding plant, with a thinner leaf, and has a wide range—it’s hardy to a lot of parts of the country. Both species impart hardiness; the combination of the different architecture has led to different shapes and sizes of Heuchera.
Q. What about sun tolerance? I get away with growing them in bright spots though not baking sun by any means in my Northeast Zone 5B garden, but some of the tags seem to sound like they’re a little more versatile in their light requirements.
A. It’s very region-specific, and a lot of the cultivars have been bred in the Pacific Northwest, where they grow beautifully in full sun—but it’s just a less-intense full sun. When they create the nursery tags that go with plants that get shipped all around the country, the have a much wider cultural range than what we in the mid-Atlantic can do. It’s a little misleading, but not their fault; they’re reporting what they’re finding.
In our region, we came down to part shade to full shade. We tested each one of our cultivars in a full-sun situation. All except the chartreuse cultivars lived, but…
Q. [Laughter.] “They all lived, but…” Not the best result when you’re designing a garden.
A. Yes—the others lived, but they all looked better in the shade.
Q. At different seasons of the year they can also look different, yes?
We planted our trial [above] in the springtime, and wanted to organize it by color. We had a gradual fading of color throughout the area. But by summertime you’d think I had no idea what colors I was looking at in springtime—like I was colorblind. They change so much. Generally they have darker, more prominent colors in the springtime. It’s really the new foliage that comes along in the cool weather that has the bright color to it. Sometimes you’ll see it as more purple to the leaves; other times you might see prominent venation—a darker or red vein that’s very showy.
A lot of times you’ll see those colors come out again in the fall if there’s a flush of new growth.
Q. Before we talk about favorites or best ones: These are funny plants. They don’t have a big root system, and have this sort of knobby thing that sticks up above the ground. If you transplant too late in the fall, they can heave out of the ground in the winter—oops! Can you talk about growing them well?
A. The structure is weird—kind of alien-ish, with a thick almost woody stem that essentially gets longer and longer each year.
When people talk about dividing Heuchera, what they really mean is preventing that stem from getting so tall that it gets damaged by yourself, or animals, or drying winter winds that dry out the growing tip.
What’s mean by dividing is really digging them up, and replanting them a little deeper.
A good way to describe it is almost like rings of a tree. In a tree, the rings are growing out, in diameter. In Heuchera, the rings are stacking on top of one another. Each year it gets taller and taller. When you dig and replant it you want to replant it deeper, but not to bury the growing tip. You want leave an inch or two sticking out of the soil—but don’t be afraid to bury that ugly woody part.
Q. Do you ever cut off any of the nasty woody parts, or…
A. When it gets to the point when a Heuchera is showing those woody parts, that’s when you want to sort of shake it and tease it apart, and those portions will naturally fall away. Then replant the rest.
Q. Any pests or diseases in Heuchera?
A. The one we experienced most in the trial was root rot. We had a lot of instances of extremely heavy rainfall, which is sort of a natural killer for Heuchera. They naturally grow in rock crevices or rocky ground.
Q. I did not know that. But it makes sense with that thick structure we’ve just been talking about.
A. They’re realty great for containers, or under trees—where things are much better draining, or drier.
Q. Any pests?
A. We had a little Japanese beetle damage, but it wasn’t a very troublesome pest. Black vine weevil is a notorious garden pest for a lot of genera, including Heuchera, which are very susceptible. We didn’t see it in our trial.
The thing to watch for is that vine weevils make this characteristic D-shaped hole in the leaf. What that means is there are adults feeding on the leaves. Adults don’t do any long-lasting damage, but that’s an indication they’re there and you need to think about treating them. It’s actually the larval stage that’s a problem, feeding at the roots. An application of beneficial nematodes is the best treatment there; I think early spring is when they are most active, and the time to treat them.
Q. From a design standpoint, how do we use them?
A. I like the larger Heuchera in masses. They look really nice that way, and it can help to create a foil for more dramatic plants that have showy blooms. Some of the more open plants—the villosa types—have a more open architecture, so they knit together very well.
Q. Those are my favorites. They make a great groundcover, but not in the negative connotation of groundcover as in: monochrome boring.
A. It’s not like a flat plane, or boring, no. Some of the ones that are more visually like concrete mounds don’t necessarily look so great in masses, but are really nice for a repeating throughout the garden to tie a design together.
Q. But they don’t knit so well.
A. They’re more gumdrop-like in the landscape.
Q. I love Heuchera in containers—and use them as my foliage element in my “annual” pots, and then take them out of the pots and heel them into my empty vegetable garden in the winter, to use again next year. In really big pots, I can even overwinter them in the garage still planted.
A. They’re really great in pots, because it’s interesting foliage all year. A lot of people may live in urban areas where there’s not a lot of sun on a balcony, for instance, so having a shade-loving plant in a pot that’s colorful for a long time is special.
Q. A variety like ‘Citronelle’—and I was so happy to see it as a favored variety on in your report—is a favorite for using as like a “ruff” at the foot of taller container plants. It doesn’t spill like the chartreuse sweet potato vine, but it’s the same color.
A. And it’s perennial, so you don’t have to buy it every year.
Q. Other great ones?
A. ‘Frosted Violet,’ which is maybe not well-known, but people “in the know” have known it for awhile. It’s a nice villosa type that’s bright purple with some silver highlights, and has a great floral display—unique among our top performers.
A. No surprise—a lot of gardeners have had experience with it, and it’s a dependable cultivar that holds its own pretty well in the garden.
Q. What I get upset about: I have had it for years, and used and repeated it—but then when I went to buy more, nobody had it. The nursery had gone on to the next cultivar. We should say that it’s not caramel-colored exactly, but maybe peachy and…
A. …it depends on how much sunlight it’s getting. It can be a hard plant to design with because it can be dramatically different shades—peachy-yellow, maybe.
Q. So I was like, “No, don’t do that to me!” at the garden center. I wanted ‘Caramel.’ [Laughter.]
A. It’s funny you mention that, because there is actually another cultivar, ‘Southern Comfort’ [above], which is a very similar color scheme. It’s another large villosa type, but it’s not quite as dense—more open, relaxed looking plant. I actually like it a lot more than ‘Caramel.’
A. One that’s overlooked but has been on the market a long time: ‘Bronze Wave’ [above]. It’s honestly not the showiest plant—this purplish-green color—but it’s one of the most dependable plants from our trial and good as a filler that will be a foil for other plants in the garden.
A. That’s the one plant I took home from the trial. It has this beautiful, unique blue-green color to the foliage, which wasn’t common to the other cultivars we looked at. Plus it has a great floral display: bright bubblegum-pink flowers on top of the blue-green foliage. And it was a very consistent performer year to year.
The only problem is that nobody’s growing this plant; it’s my mission to get it out there.
Q. ‘Steel City:’ George Coombs’s mission, when he’s not trialing 83 Heuchera cultivars! What else are you trialing at Mt. Cuba this year?
A. We’re trialing Monarda, Baptisia, and we just started a huge Phlox trial. We’re doing shade-loving Phlox as well as the typical garden types.
- Visit Mt. Cuba
- Get the report on Heuchera research (pdf)
- All the Mt. Cuba trial reports (including on asters, annual coreopsis and coneflowers)
- My previous interview with George Coombs
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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its sixth year in March 2015. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the April 6, 2015 show right here, and also use the buttons below to subscribe to future shows, free.
(Photos courtesy of George Coombs.)