Rhododendron & Azalea

RHODODENDRON

Of all the shrubs that flower in spring, rhododendrons—especially the azaleas—provide some of the most brilliant displays. I have them planted together with tree peonies in a garden just outside my Summer House, and when they bloom this time of year, they make one corner of my farm erupt with spectacular color.

Azaleas can thrive in a wide variety of growing conditions, which makes them useful in many different landscapes. They are popularly referred to as the “royalty of the garden”—long adored for their brightly colored flowers and semi-evergreen foliage. Plant enthusiasts have selectively bred azaleas for years, producing thousands of different cultivars. My azalea collection is in a lightly wooded area near my blooming tree peonies, where they get filtered sunlight through the day—something they both prefer.

Azaleas are flowering shrubs in the Ericaceae family, which includes blueberries and mountain laurel, and are members of the genus Rhododendron. Some varieties can bloom as early as March, but most bloom in April or May, with blossoms lasting several weeks. The plants can survive for many years, and they continue to flower their entire lives.

Right nearby Skylands, in Maine, is the Asticou Azalea Garden. The garden, part of the Asticou Inn, was designed and built in 1956 by the owner, Charles K. Savage. In 1955, Beatrix Farrand, the renowned gardener and landscape architect, announced her plans to dismantle her fabulous gardens at her Reef Point estate in Bar Harbor. With the financial help of John D. Rockefeller, Jr., Savage was able to acquire many of those botanical specimens and fulfill his dream of building Asticou Azalea Garden, modeled after a classic Japanese design. In early spring, the garden begins with a flourish of cherry blossoms followed by a colorful explosion of azaleas in every imaginable shade. The garden is owned and maintained by Mount Desert Land and Garden Preserve and a committee of volunteers. One year not too long ago, after a stroll through Asticou with my own gardener from Katonah, we got many good ideas for what to plant around the pond on the farm, most notably the beautiful azaleas.

I had never considered rhododendrons or azaleas important as cut flowers until I started to experiment with them in springtime arrangements. Mixed with other seasonal perennials and bulbs, these amazing woody-stemmed flowers gave structure and shape to bouquets that could not be achieved with other flowers. Additionally, the florets are somewhat orchid-like in importance, and can also stand alone in small containers as a sort of specimen display that is colorful, interesting, and one of a kind.

At Turkey Hill, I had none of these cultivars, but at the farm on Bronson Road, in Fairfield, Connecticut, I did have an incredible fifty-year-old rhododendron hedge that measured more than 300 feet long and almost 20 feet high. It bloomed each spring for about three weeks—thousands of perfect clusters of mauvish rose flowers on shrubs covered in shiny elongated green leaves. Pruning a hedge like that did not detract from its glory, and I made giant arrangements for my home with just a few carefully chosen branches that arguably needed to be pruned, anyway!

I hated to leave that hedge; I miss it still. In East Hampton, where azalea and rhododendron grow profusely and thrive in the moist sea air, I have a similar though much smaller hedge, but it was not until I got my farm in Katonah that I started to study the culture of these spectacular shrubs in depth.

This versatile glass multichamber vase holds vibrantly orange ‘Mandarin Lights’ 
azaleas and boughs of variegated green-and-white Solomon’s seal. “I took my cues from the shape of the anthers,” Kevin explains. “I wanted
to continue the spreading and expanding movement within the blossom. When you’re looking at the arrangement, your eye finds the green and moves inward to the azalea; but when I was making it, I started with the azalea and then added the Solomon’s seal.” The pretty blossoms may shed here and there; place flower heads in smaller vessels alongside, like these antique syllabub firing glasses. “Some people like to separate groups of arrangements like these,” he says, “but I keep them together to continue the story.”

The garden around the Summer House in Katonah erupts in color every spring when a cluster of azaleas and tree peonies bursts into bloom. Azaleas can thrive in a wide variety of growing conditions, which makes them useful in many different landscapes.

GROWING & ARRANGING

ALL AZALEAS ARE RHODODENDRONS, BUT NOT ALL RHODODENDRONS ARE AZALEAS. THE GENUS BOASTS HUNDREDS OF SPECIES AND THOUSANDS OF HYBRIDS AND CULTIVARS IN AN ASTOUNDING VARIETY OF COLORS, TEXTURES, SHAPES, AND SIZES—FROM TINY 2-INCH AZALEA BLOSSOMS TO “BIG-LEAVED RHODIES” WITH 3-FOOT FOLIAGE.

My dedicated azalea bed in Katonah contains several varieties to provide more visual interest. We sited the large bed in a shady, wooded area where the shrubs can get filtered sunlight throughout the day.

HOW TO GROW

The difference between azaleas and other rhododendrons is not strictly defined; generally, rhododendrons are evergreen and azaleas are deciduous or semi-evergreen (meaning they keep their leaves at the tips of their branches throughout the winter). The number of stamens is another indicator: Most azaleas have five, while other rhododendrons have at least ten. Azaleas and other rhododendrons have bloom times that range from early spring through midsummer, and their flowers come in almost every color of the rainbow. Azalea flowers are typically funnel-shaped, while other rhododendrons have bell-shaped blooms with thicker petals. All are quite easy to grow.

ZONE Some rhododendrons are more amenable than others to very cold winters or very hot summers, so it’s important to choose one that is right for your zone. Some varieties are hardy to Zone 4 and others only to Zone 6. The tropical group known as Vireyas is hardy in Zones 10 and 11. Rhododendrons often have shallow roots and should be mulched well for winter; evergreen varieties benefit from winter protection in cold areas. The stems of azaleas, which are thinner than those of rhododendrons, can be brittle in cold weather, so they are best situated away from heavily trafficked areas.

SOIL Rhododendrons (including azaleas) flourish in acidic soil (pH 4.5 to 6). Soils in rainy areas tend to be acidic, while those in arid regions can be more alkaline. Avoid planting in soil near a house’s foundation, as the cement may leach alkaline material. Test and amend with organic matter as needed (coffee grounds, finely milled pine bark, peat moss, or composted leaves are good choices); make sure your soil is not only acidic but also rich, moist, and well draining. Rhododendron roots can be relatively shallow; spread mulch to keep the roots cool and moist.

LIGHT Rhododendrons (including azaleas) prefer shady sites with a few hours of filtered light each day. Don’t give them full sun, especially in warmer climates.

CHOOSING When selecting shrubs to plant, always examine the root systems. Make sure the roots are strong, with even branches and no signs of disease. With potted options, choose a plant that is not flowering. Like lilacs and other shrubs, the plant directs all its energy into flowering in order to fulfill its primary goal of reproduction; this leaves the unestablished root systems without proper nutrients. Healthy roots produce better plants. You should be able to pull the whole plant and root system out of the pot, without the roots breaking off—and without seeing endless circles of roots around the inside of the pot, a sign that it’s been sitting too long. Look for medium-dark green leaves; avoid pale foliage.

PLANTING Plant in the spring about an inch below the surface. Apply a fertilizer for acid-loving plants along with a top dressing of high-quality organic mulch and compost. For the Katonah azaleas, we also use Azomite, which boosts the mineral content of the soil.

WATERING Keep the soil around rhododendrons (including azaleas) moist and spongy but well drained. Their root systems are quite shallow and can dry out easily, so remember to water a few times a week (or more frequently during hot spells).

PRUNING Because many rhododendrons flower on branches that are at least a year old, having set flower buds the summer before, it’s best to prune your shrub right after it blooms, and only when needed (if, for example, you notice that the plant is beginning to crowd its neighbors). Think of it as deadheading taken to the next level. Rhododendron leaves erupt in a rosette around the stem; to prune, cut branches back to just above one of the whorls. Below each whorl are the dormant, slender leaf buds that will develop. Cut no more than 15 to 20 inches, and try not to shorten a branch by more than half. If you’ve inherited a truly ungainly plant, it may take a few seasons (or years) to finish the pruning process without inflicting too much damage. At the farm, we tend to cut off only dead or broken branches—rhododendrons have an elegant natural habit (the term for the growing shape of the plant) that is best left alone.

As for azaleas, paying attention to nodes is unnecessary for many of them; there are so many latent buds that the branch will flower no matter what. Azaleas can become bare in the middle, with leaves only at the tips. To help your shrub regain fullness, thin outer branches in order to expose smaller inner ones; the additional sunlight they receive will encourage them to fill in. Or cut off just a couple of inches every year (this is called tipping back), which stunts some growth at the end of the branch, keeping the plant full rather than letting it spread out.

TROUBLESHOOTING If your azalea plant is diseased, has suffered winter cold damage, or is simply aged and ungainly and requires a total overhaul, try a rejuvenation: In late winter or early spring, before new growth starts, cut all stems to about 8 inches above the ground. (Don’t try this with larger rhododendrons, including Rhododendron fortunei and R. arboreum, or many hybrids and smooth-barked varieties; none will respond well when cut way down.) Before a rejuvenation, prepare the plant by fertilizing and mulching it in the spring, to promote vigorous root growth. Fertilize again after growth resumes in the spring following the rejuvenation, and water during any dry spells that summer. You may lose a year or two of great azalea blooms, but in the end your plant will grow back healthier and fuller.

Rhododendrons (including azaleas) can be susceptible to a fungal condition called root rot, caused by a mold in the soil, especially when newly transplanted. If you notice off-color, drooping foliage or discolored, dying roots, cut the branches 6 to 8 inches beyond the diseased portion, sterilize your tools with a solution of alcohol or water and bleach, and use fungicide to protect neighboring plants. Don’t water diseased plants from overhead, and make sure the soil is very well drained to prevent the disease.

Keep in mind that rhododendron plants can be toxic to dogs. Consider your dog’s personality when planning a garden—some animals love to chew on plants and trees, while others aren’t interested. If your pet is a fan of eating greenery and is allowed to roam free in your yard, be sure to fence off any dangerous plants.

A single, massive rhododendron flower head sits at the bottom of a wide glass punch bowl. Kevin wanted to magnify the focus on the blossom and its dark throat: “It reminds me of Japanese fighting fish,” he says. “I didn’t fill the whole bowl with water, to keep the flower head resting below the rim of the glass.” Kevin cut the stem all the way at the top and submerged the entire bottom of the flower in water. This is an arrangement that wouldn’t be as effective from far away; let it have its close-up by putting it in the center of a dining table.

Here, Kevin arranged rhododendron blossoms in a pair of Moroccan paintbrush holders. Their individual tubes allow for each short branch to reach water, and for the green leaves and containers to play off the red mophead blooms. “Anything on opposite sides of the color wheel, like red and green, will work well together in an arrangement,” says Kevin. Again, cut the flower heads short, with their collar of leaves remaining intact. Place arrangements like these down the center length of a table or buffet.

HOW TO ARRANGE

CUTTING Rhododendrons (including azaleas) are not commonly thought of as arrangement flowers; they are most often viewed from afar and never taken off the bush. But as beautiful as they appear en masse in the garden, their blossoms can be just as spectacular when viewed close-up. With most rhododendrons, cut just the flower, leaving a short stem for water intake. They have woody branches, a structure that doesn’t lend itself to cutting long stems. Use secateurs or a sharp knife to split the ends about 1 to 2 inches vertically, so the plant can take in more water, and use in low arrangements.

MAINTAINING The blossoms can be long-lived once cut. Rhododendron foliage, with its leathery green leaves, can also be beautiful, and well suited in arrangements, as it holds up for an equal length of time. Azaleas have smaller, wispier foliage, which isn’t mature when the shrub blossoms—you’ll see flowers first, and later the leaves.

ARRANGING “I always thought of rhododendrons and azaleas as filler flowers, but they’re at their best when they’re the center of attention,” Kevin says. “Their stamens have a really pretty character. They curl upward, and can add a little spark and fizz to denser arrangements of flowers like peonies.” Rhododendrons are often top-heavy, so choose a vessel with sides that can secure the flower. Azaleas are more stable and can nestle into taller vessels. Despite how full and dense an azalea shrub can look from afar, the individual branches can be fairly sparse; their smaller flowers mix well with other blooms, such as tulips or peonies. The biggest step is simply remembering to bring these blossoms inside. Cut a rhododendron short and put it in a glass, or embrace the idea of small flowers in multiples when you have a big bunch of azaleas (as shown on this page).

Cut rhododendron flower heads are arranged in a collection of small glasses, set on tiered American pressed-glass cake stands for an epergne effect. (French epergnes were tiered bowls or trays traditionally made of silver, but glass came into use at the beginning of the twentieth century.) Kevin mimicked the effect with a drinking glass at the top and short glasses all around.