LSU AgCenter Horticulturist
Welcome spring! In the Louisiana landscape, nothing heralds the first official day of the season like the azalea and its grandiose flowers. It is one of the most commonly used ornamental plants in both home and commercial landscapes. The Indiana azaleas (Rhododendron indicum) can be found prominently alongside the stately oaks of the Baton Rouge campus of Louisiana State University.
Azaleas are natives of Japan like our winter-blooming camellias. They are characterized by a broad, mounding growth habit and grow to an average size of 6 feet high by 6 feet wide. Some varieties are more compact at 2 feet by 2 feet, and others grow up to 10 feet by 10 feet.
Azaleas can be grown in full sun to partial shade. They are often planted as an understory plant to oaks and pine trees. Most types bloom in the spring, but some varieties offer later-season blooms. There are many colors from which to choose, and there also are compact varieties that can be used in smaller planting spaces.
Spring is a great time to plant azaleas. I must admit that as a younger horticulturist, I was not the azalea’s biggest fan. I thought they were overused, they were only interesting in spring and those hairy, itchy leaves that irritated my skin used to, well, get under my skin! However, I have renounced my dislike and embraced this gorgeous staple of the Southern garden in my older, wiser age.
Azaleas should be planted in well-drained soils in a raised bed of 4 to 6 inches. A soil pH of 5.0 to 6.0 is crucial for success. Perform a soil test where you plan to plant and amend the soil with elemental sulfur, aluminum sulfate or ammonium sulfate to help bring the pH down, if needed.
Fertilize in late winter and early spring for the best blooms and greener foliage. Apply a general-use or an azalea-camellia fertilizer. Be sure to mulch your beds to conserve soil moisture, suppress weeds and provide a source of organic matter. Prune after flowers have bloomed, removing a small amount of wood annually to keep plants compact and to thin out tall, spindly stems.
Lacebugs, bark scale and spider mites are common pests of azaleas. Look for bronzing on older leaves as a sign of spider mites and mottled or tiny brown spots on the leaf when lacebugs are present. Lacebugs will be found on the underside of leaves, making them more difficult to control and causing a serious problem in late winter and early spring. Lacebugs can be controlled with a systemic insecticide. Mites and scale can be controlled with insecticidal soap sprays. Horticultural oils may be used on cooler, cloudy days. Remember, you must re-treat both in seven to 10 days to kill newly hatched pests.
Common disease problems include petal blight, leaf gall and root rot. These diseases will cause spots, wilting and overall plant decline. They are caused by fungal pathogens and are best controlled by following good management practices, including proper drainage and optimal growth conditions. Fungicide treatment should be a last resort. Contact your local AgCenter agent if you need help identifying and solving your plant health problems.
Some of the most gorgeous and commonly grown azaleas are the Indian azaleas, whose flowers can grow anywhere from 2 to 3 1/2 inches across for the most grandiose display. Formosa, Dixie Beauty, George L. Tabor and Mrs. G.G. Gerbing are by far the stars of this category. There are several other varieties of Indian azaleas, including Daphne Salmon, Fielder’s White, Judge Solomon, President Clay, Pride of Mobile and Southern Charm, to name a few.
The Kurume azaleas are considered dwarf azaleas, growing 4 to 6 feet in height by 3 feet in width at a slower, denser rate. Flowers are only 1 to 2 inches across. Some of the most popular of the dwarf azaleas are Christmas Cheer, Coral Bells, Hershey’s Red, H.H. Hume, Hinodegiri and Snow.
The Satsuki azaleas bloom later in the spring, typically in April and May. Popular varieties are Gyokushin, Pink Gumpo, Pink Macrantha, Red Gumpo, White Gumpo and Hardy Gardenia.
For a complete list, description and details of each variety listed above, visit www.lsuagcenter.com and search for “azalea publication 1295.”
I would be remiss if I did not mention the Encore azaleas invented by plant breeder Robert “Buddy” Lee, of Independence, Louisiana, who has developed 31 varieties. The Encore azalea is prized for blooming in the spring, summer and fall. Retired AgCenter horticulturist Allen Owings performed studies with Encore azalea varieties to determine an average of 21 to 32 weeks of bloom. His top five variety picks are Autumn Embers, Autumn Royalty, Autumn Fire, Autumn Twist and Autumn Princess.
I also should mention the Conversation Piece Azalea, which was a 2012 selection of the AgCenter Louisiana Super Plant program. Belonging to the Robin Hill family of azaleas and noted for their large flowers, nearly 4 inches across, they are repeat bloomers and hardy.
Lastly, I must mention the native azaleas. Natives are deciduous, unlike their evergreen Asian counterparts. Their primal beauty cannot go without mention. They attract hummingbirds, butterflies and other pollinators with their colorful, nectar-rich flowers. Flame of Florida azalea (Rhododendron austrinum) and Honeysuckle azalea (Rhododendron canescens) are two found readily at your local nurseries.
Go get your hands on some azaleas this weekend and Get It Growing!
The George L. Tabor azalea is one of the most commonly grown azaleas. This variety offers pink blooms that can grow 2 to 3 1/2 inches across. Photo by Heather Kirk-Ballard/LSU AgCenter
The Red Formosa azalea is a commonly grown variety that features colorful blooms. Photo by Heather Kirk-Ballard/LSU AgCenter
The Honeysuckle azalea is a deciduous native azalea variety that attracts pollinators with nectar-rich flowers. Photo by Bob Mirabello/LSU AgCenter
The Flame of Florida azalea is a deciduous native azalea variety that attracts pollinators with nectar-rich flowers. Photo by Bob Mirabello/LSU AgCenter