Q. Some of the leaves on my azalea and/or camellia are swollen and light green. What caused this?
A. This is caused by a fungus that has been relatively common this spring.
The fungus Exobasidium vaccinii causes leaves and flowers to become swollen or thickened, curled and waxy in appearance. This fungus causes leaves, and in some cases flower petals, to enlarge abnormally and is commonly referred to as azalea or camellia leaf and flower gall.
Exobasidium leaf gall on camellia. Credit: Larry Williams
Symptoms vary somewhat based on the host plant. In addition to azalea and sasanqua camellia, it can occur on blueberry, as well. Infected blueberry leaves turn an unusual bright red in spring with almost no swelling of tissue. With azaleas and camellias, leaves become large and distorted and eventually a white powder covers the galls. The white growth consists of spores, which is how the fungus reproduces. Galls ultimately turn brown and harden. Not every leaf will be infected. It’s more common for the plant’s lower leaves to be the most heavily infected but under humid conditions and in shaded locations galls may form on leaves throughout the plant canopy.
The disease relies on airborne spores produced in the whitish mold on the surface of galls in late spring to early summer to reproduce. The galls then form the following spring. It’s important to remove and dispose of infected leaves before they turn white with spores.
Once you see evidence of infected leaves, it’s too late for chemical control. Besides, there currently is no effective or practical fungicide to control this disease in the home landscape. But you can reduce the amount of infection on your plants the following year by pruning infected leaves and throwing them away before spores are produced. After removing infected leaves with galls, never leave them on the ground around the plants.
It’s best to bury, burn or place the infected leaves in a plastic bag and throw them away. This disease is more severe during a cool, wet spring. It’s advisable to not add to the problem by artificially providing the “wet weather” the spores need by frequently using an overhead sprinkler and keeping the foliage wet in the spring during disease development. This is exactly what this and many other plant diseases need – wet conditions. Yet another reason to water during early morning and on an as needed basis, versus allowing an irrigation system to frequently run when there is already adequate moisture from rain.
In the home landscape, the fungus does not cause any long-term problems for the plant. It just makes the plant’s leaves look ugly. The infected leaves will usually fall prematurely.
When to prune a particular shrub can be a confusing practice for even the most experienced gardener. Luckily there are many plant guides to help remind us of pruning times or even a quick call to your local Extension office.
Now that we finally remember the best time to prune azaleas or French hydrangeas, the nursery throws us a loop with everblooming plants. Although not new, the Encore® series of azaleas and Endless Summer® collection of hydrangeas have the wonderful characteristic of blooming repeatedly throughout the growing season. When is the best time for pruning these repeat blooming shrubs?
In general, if you select your Encore® azalea carefully, it should need very little pruning. There are many sizes available to fit every space. Reduce your need for pruning by choosing a selection that will not outgrow your space. For example, Autumn Sangria® is a larger selection to at least 4-5 feet tall while Autumn Embers® is about 3 feet tall. If your plant needs a little selective pruning, the best time to prune is still after the first initial big bloom in April.
Encore Sangria has vivid pink flowers. Photo by Beth Bolles, UF IFAS Extension Escambia County.
Pruning time for Endless Summer is the same for other mophead hydrangeas even though it blooms on both old and new wood. You may selectively prune after the first bloom. It is always fine to deadhead faded blooms back to the first healthy buds.
While the azalea blooms are beautiful, it’s hard to remember what the leaves looked like last summer. But, if you look carefully, you may see some off-colored, bleached out leaves. Those are from a piercing-sucking insect. Its azalea lace bug, Stephanitis pyrioides. They overwinter as eggs on the underside of infested leaves or in the leaf litter or mulch under the shrub. Eggs hatch in late March and early April. The insect then passes through five nymphal instars before becoming an adult. It takes approximately one month for the insect to complete development from egg to adult and there are at least four generations per year. Valuable plants that are susceptible to lace bug damage should be inspected in the early spring for the presence of overwintering lace bug adults, eggs and newly hatched nymphs. Inspect these plants every two weeks during the growing season for developing lace bug infestations.
Damage caused by azalea lace bug, Stephanitis pyrioides (Scott), feeding. Photograph by James. L. Castner, University of Florida.
Both adults and nymphs have piercing-sucking mouthparts and remove sap as they feed from the underside of the leaf. Lace bug damage to the foliage detracts greatly from the plants’ beauty, reduces the plants’ ability to produce food, decreases plant vigor and causes the plant to be more susceptible to damage by other insects, diseases or unfavorable weather conditions. The azalea can become almost silver or bleached in appearance from the feeding lace bug damage.
Adult azalea lace bug, Stephanitis pyrioides (Scott). Photograph by Jamba Gyeltshen, University of Florida.
However, lace bugs often go undetected until the infested plants show severe damage sometime into the summer. By then several generations of lace bugs have been weakening the plant. Inspecting early in the spring and simply washing them off the underside of the leaves can help to avoid damage later and the need for pesticides.
Adult lace bugs are flattened and rectangular in shape measuring 1/8 to 1/4 inch long. The area behind the head and the wing covers form a broadened, lace-like body covering. The wings are light amber to transparent in color. Lace bugs leave behind spiny black spots of frass (excrement).
Lace bug nymphs are flat and oval in shape with spines projecting from their bodies in all directions. A lace bug nymph goes through five growth stages (instars) before becoming an adult. At each stage the nymph sheds its skin (molts) and these old skins often remain attached to the lower surface of infested leaves.
Azalea leaf with azalea lace bugs, Stephanitis pyrioides (Scott), and excrement spots. Photograph by James. L. Castner, University of Florida.
Azalea lace bug eggs are football-shaped and are transparent to cream colored. Lace bug eggs are found on the lower leaf surface, usually alongside or inserted into a leaf vein. Adult females secrete a varnish-like substance over the eggs that hardens into a scab-like protective covering. Other plant species, such as lantana and sycamore, may have similar symptoms. But, realize that lace bugs are host specific. They feed on their favorite plant and won’t go to another plant species. However, the life cycle is similar. Be sure to clean up all the damaged leaves. That’s where the eggs will remain for the winter. Start next spring egg-free.
Piedmont azalea (Rhododendron canescens) flowers. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
Native azaleas are stunning this time of year. These deciduous shrubs (and sometimes small trees) often go unnoticed until they bloom in the spring. Three species native to Florida are the piedmont azalea (Rhododendroncanescens), the Florida flame azalea (Rhododendron austrinum), and the swamp azalea (Rhododendron viscosum). Piedmont azaleas have whitish to pinkish blooms, Florida flame azaleas have yellow to orange blooms, and the white blooms. All three species have a wonderful honeysuckle-like, sweet fragrance. All three serve as outstanding focal points in the landscape.
Native azaleas and other deciduous azaleas have varying site preferences. Like other azaleas, piedmont and Florida flame azaleas prefer moist, well-drained, acidic soils. However, as the name would suggest, the swamp azalea tolerates wetter locations. All three species prefer partial shade (morning sun and afternoon shade are best) locations and can grow up to 15 feet tall.
Rhododendron x ‘Aromi Sunny-Side-Up’ in bloom. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
In addition to these beautiful native azaleas, a number of deciduous hybrids have been developed. Aromi hybrids have been bred to tolerate heat and humidity. These azaleas were developed from four native species ()from Gene Aromi in Mobile, AL. He developed more than 100 cultivated varieties (also referred to as cultivars). Popular cultivars in the market include ‘Centerpiece’, ‘Aromi Sunrise’, and ‘Aromi Sunny-Side-Up’.
Deciduous azaleas do not require a lot of fertilizer. A controlled release or slow release, acid forming (specifically formulated for azaleas or blueberries) fertilizer is recommended. A fertilizer nutrient ratio of or close to 2-1-1 (N-P-K) should be selected. Plants should be fertilized in spring or early summer, never in the fall or winter.
Article written by Dr. Gary Knox, North Florida Research & Extension Center – Quincy, FL.
‘Gumpo Pink’ flowers are 3 inches in diameter and are pink with purplish pink dots and occasional white blotches on petals.
Background
In the times before re-blooming azaleas like Encore®, Bloom-A-Thon® and others, Satsuki azaleas were valued for late flowering that extended the azalea “bloom season”. Even with modern re-blooming azaleas, Satsuki azaleas still are appreciated as refined evergreen shrubs for the sophisticated garden or discerning plant collector.
“Satsuki” means “Fifth Month” in Japanese, corresponding to their flowering time in much of Japan. These azaleas were developed hundreds of years ago from their native Rhododendron indicum and R. eriocarpum. The Japanese selected cultivars more for their form and foliage than for flowering. These beloved plants were used in gardens as sheared boxwood-like hedges or pruned into rounded mounds that might resemble rocks or boulders in classical Japanese gardens. Their size and form also made them well adapted for training as bonsai. Most of the Satsuki azaleas in America were introduced in the 1930s by USDA.
Description
Satsuki azaleas are small evergreen shrubs that flower in April and May in north Florida, long after most older type azaleas have finished. Satsuki azaleas also are known for producing large, mostly single flowers up to 5 inches in diameter in colors of white, pink, red, reddish orange and purple. Often the flowers will include stripes, edging, blotches, spots or flecks of contrasting colors (Sometimes all on the same plant!) with more than 20 different color patterns recorded.
Satsuki azaleas have an elegant subtle charm, quite unlike the flashy, over-the-top, heavy blooming all-at-once Southern Indica azaleas like ‘Formosa’ and ‘George L. Taber’. Typically, Satsuki azaleas display a few large blooms at a time, allowing one to better appreciate their size and color patterns as contrasted against their fine-textured, dark green leaves. To make up for a less boisterous display, Satsuki azaleas flower over a longer timeframe, averaging about 8 weeks, with some flowering an amazing 14 weeks. In another contrast, most Satsuki azaleas grow smaller in size, in my experience reaching about 3 feet tall and wide in a five-year timeframe. The rounded to lance-shaped leaves of Satsuki azaleas also are demure, ranging in length from just ½ inch to no more than 2 inches.
Culture
Satsuki azaleas enjoy the same conditions as most other azaleas: light shade and moist, rich, well-drained soil. Mulch regularly to maintain organic matter and help hold moisture. Fertilize lightly and keep the roots evenly moist. Minimal to no pruning is required. Satsuki azaleas also are well adapted to container culture. Their small size and fine textured leaves make these a favorite for bonsai enthusiasts since their small leaves, branching habit and mounded form naturally make them look like miniature mature “trees”.
Sources and Cultivars
Look for Satsuki azaleas in spring at garden centers or year-round at online nurseries. There are hundreds of cultivars but some popular types to look for include:
Gumpo Pink – 3-in. diameter light pink flowers with purplish pink dots and occasional white blotches
Gumpo White – 3-in. diameter white flowers with occasional pink flakes and light green blotches
Gyokushin – 3-in. diameter flowers are predominantly white but with light to dark pink dots and blotches
Higasa – flowers are 4 to 5 inches in diameter and are purplish pink with purple blotches
Shugetsu – also called ‘Autumn Moon’, 3-in. diameter flowers are white with a broad, bright purplish-red border
Tama No Hada – flowers are 4 to 5 inches in diameter and are white to pink with deep pink stripes; usually flowers in fall as well as spring
Wakaebisu – 2.5-in. diameter flowers are “double” (hose-in-hose) and are salmon pink with deep pink dots and blotches; this also flowers in fall as well as spring
References:
Chappell, M. G.M. Weaver, B. Jernigan, and M. McCorkle. 2018. Container trial of 150 azalea (Rhododendron spp.) cultivars to assess insect tolerance and bloom characteristics in a production environment. HortScience 53(9-S): S465.
‘Gumpo Pink’ flowers are 3 inches in diameter and are pink with purplish pink dots and occasional white blotches on petals.
‘Gyokushin’ flowers are white with occasional pink flecks and light green blotches.
‘Shugetsu’ has 3-inch flowers that have bright purplish-red border on edges of petals.
Galle, Fred C. Azaleas. 1985. Timber Press, Portland, Oregon. 486 pp.
