Azaleas are more than a harbinger of spring. All across the Southeast, masses of red, white, pink and purple azaleas boldly proclaim that the season has arrived. Many people think azaleas come in just four colors, and some may even criticize their use as commonplace. Discriminating gardeners know better. This article cannot possibly discuss everything about azaleas, but it may foster an appreciation for their amazing diversity while providing some practical advice.
All azaleas are really rhododendrons, and fall into two general categories: evergreen or deciduous. Evergreen azaleas are very common in American gardens but they are not native plants. They all originated in western Asia, primarily Japan and China. North America is home to 17 native azalea species and they are all deciduous shrubs. Surprisingly, most are native to the Southeast! Admired in Europe since the 1800s, they have been woefully underrepresented in our gardens.
Many azaleas bloom so profusely that the foliage can be completely obscured. That does pose some special landscaping problems. With well over 6,000 named cultivars, designers are often unfamiliar with new varieties but must select colors that will harmonize with other landscape features. Brilliant azaleas attract attention but they can be overpowering at times. They can clash with other colors but liberal use of white can help alleviate design problems. Delicate pastel shades are more forgiving. Azaleas transplant easily, so mistakes are easily corrected with a shovel.
In large landscape plantings, masses of the same azalea variety give the best effect when viewed from a distance. When mature, those plants will grow together creating a single mass appropriate to the scale. Patchworks of mixed colors can be effective in small alcoves.
Subtle flower features like stripes, blotches, multicolored sports, or blossoms with contrasting borders are best appreciated up close. Double and ruffled azaleas or those with unusual flower forms like ‘Koromo Shikibu’ and ‘Wagner’s White Spider’ with their strap-like petals deserve that same close admiration.
Many azaleas are fragrant, and perfect for intimate garden spaces. Every garden should have at least one ‘My Mary’, a very fragrant yellow native azalea hybrid.
For many of us, no man-made garden can possibly compare to the beauty of our native azaleas as they occur in the wild. Early plant explorers considered them among the most impressive flowering plants yet known. Many of us agree, and make annual pilgrimages to the southern Appalachians to witness spectacles like the flowering of yellow, orange and red flame azaleas (Rhododendron calendulaceum), or the multi-colored native azalea stand on the top of Gregory Bald in the Great Smoky Mountains National Park.
One rare red native species, R. prunifolium, flowers in July and August. Wild populations in Providence Canyon, Ga., seem unfazed by 100 F temperatures and it is the signature plant of Callaway Gardens. Not all native species are heat tolerant, but the “Maid in the Shade” series from Transplant Nursery and the Aromi hybrids make excellent alternatives.
Flowers only last a few weeks, so always consider a plant’s merits the rest of the year. Some azaleas may have dull foliage but others have very attractive leaves. The glossy, rounded leaves of ‘Glacier’ are legendary, but there are many standouts. Some azaleas have variegated foliage, and the leaves of others may turn dark burgundy during the winter, like a new introduction from Germany called ‘Maraschino’. Some leaves can be small, reminiscent of boxwood, but ‘Segai’ has long, narrow leaves that almost look like blades of grass.
With deciduous azaleas, leaf characteristics vary and many turn brilliant colors in the fall. Planting them among evergreens can disguise their bare winter branches.
This slow growing Satsuki azalea in the U.S. National Arboretum bonsai collection has been in training for over 30 years. The Japanese cultivar, ‘Kyoraku’, has small white flowers bordered in pink.
Large-growing varieties are perfect for screening, creating garden rooms, or providing a backdrop for wildflowers or perennials. The purple ‘Formosa’ and pale pink ‘George Lindley Taber’ are favorites in the South but may have difficulty in colder climates. Many Glenn Dale azaleas are hardier, like the bright pink ‘Dream’ that can easily reach 10 feet high and spread 25 feet across. Dwarf varieties like ‘Kazan’, ‘Sandra’s Dwarf White’, and slow-growing Satsuki azaleas make wonderful rock garden companions or bonsai subjects.
Azalea flowers can range from ½ to 5 inches across depending upon the cultivar. Members of the American Rhododendron Society in the Southeast Region selected a huge, pale lavender-pink developed by Dr. Sandra McDonald called ‘Venus’ Baby’ as their “2015 Azalea of the Year.” Rare cultivars and new releases are often hard to find unless one frequents plant society sales or specialty nurseries.
Re-blooming azaleas are very popular. Buddy Lee developed the Encore azaleas by crossing a Taiwanese species, R. oldhamii, with other azaleas. He has now introduced 29 hybrids, and recently released a double, dark red called Autumn Fire (‘Roblex’).
Planting an azalea in the right location is important, but requirements may differ depending upon the variety. In general, evergreen azaleas do best with dappled to high open shade. Plants can take more sun but the flowers do not last well. Salmon, coral, and orange red flowers are especially prone to sun damage. Evergreen azaleas grown in strong sun do become prone to an insect pest called lace bug. This small insect lives underneath the leaves and sucks out the chlorophyll leaving tiny white dots on the leaf surface. There are sprays to control lace bug, but they also kill beneficial insects that eat those pests.
Unusual flower forms deserve close scrutiny, like ‘Wagner’s White Spider’ (left) with its strap-like petals, or the fully double, ivory colored blossoms of ‘Secret Wish’ (right) that look almost like rose buds unfurling.
Deciduous azaleas require more sunlight than evergreen azaleas, at least three to four hours of direct sun daily to bloom well. In shade, they often survive but grow slowly and rarely bloom.
Azaleas prefer a moist, well-drained, acidic soil rich in organic matter. In heavy soils, consider planting in raised beds. When planting a container plant, break up the root ball to encourage roots to start growing into the surrounding soil. It helps the plant become established. Azaleas are very shallow rooted, so always set the plant at the same level or even slightly higher than the existing soil. Azaleas should be mulched well to maintain soil moisture.
Be careful with fertilizer since the amount azaleas can utilize depends upon light intensity. The stronger the sun, the more fertilizer a plant might need. It is better to apply two weak applications spaced far apart than risk burning delicate roots with excessive fertilizer. Fertilize after blooming, but avoid late summer or fall applications because plants don’t become dormant which can cause winter damage.
Heavy pruning should be done in late winter while plants are still dormant. Don’t remove more than one-third of the branches at a time since it can weaken the plant. General pruning to shape plants is done in the spring and early summer, but avoid pruning after mid-July since azaleas will be forming flower buds. Also avoid fall pruning since it encourages late season growth vulnerable to winter damage.
Try growing some unusual azaleas varieties this year, and find a place for a few native azaleas, too.
With so many thousands of named azalea varieties, finding sources for new and rare plants is not always easy. The famous Glenn Dale azaleas were released by Ben Morrison, the first Director of the U.S. National Arboretum, starting in 1941. He eventually introduced 454 cultivars that he selected from the nearly 75,000 seedlings he raised in his breeding project. Nurseries were bewildered with so many choices, and some excellent varieties had very limited distribution. Morrison planted an additional 800 unnamed cultivars at the National Arboretum that he never introduced. They were also excellent selections, and some are arguably better than named forms. When the Arboretum considered removing them in 2011, public outrage saved the original plantings.
The best sources for rare azaleas are specialty nurseries and plant society contacts. A list of commercial azalea sources can be found on the Azalea Society of America website. Many local chapters have public plant sales, but the rarest plants are usually offered at plant society conventions.
Azalea Society of America (ASA):
American Rhododendron Society (ARS): www.rhododendron.org
Save the Azaleas:
2016 ARS/ASA Williamsburg Convention: www.arsasaconvention2016.org
A version of this article appeared in a March 2015 print edition of State-by-State Gardening.
Photography courtesy of Don Hyatt.