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.
Extended spring weather with cool nights and frequent rain can be enjoyable for humans, but does strange things to plants, especially if dormant fungi are hanging around. Exobasidium vaccinii is a fungus that is believed to overwinter as spores attached to bark and bud scales. It can cause infection with the opening of buds in spring, creating odd shaped leaves and flowers that are referred to as galls. Infection is dependent on high humidity and moisture during bud break. Gall growth is due to plant cell division resulting from the stimulus of hyphal growth within host tissue. When galls are still soft, the fungus grows between epidermal cells, breaks the cuticle, and sporulates giving the gall a white cast. Either all or part of a leaf may become thickened, fleshy, and covered with a white bloom of spores. At first, diseased leaves are succulent and white, but they later shrink into hard, brown, gall-like bodies. Galls are composed of fungus-infected plant tissue. Older leaves are resistant to infection. Exobasidium vaccinii is most common in azaleas and camellias.
Photo by Sheila Dunning
But, other Exobasidium species are floating out there, and with just the right conditions they can deform other plants. That’s what caused this odd formation on one flower of a gardenia plant. In this case, the spores fused the sepals to the petals of the flower.
Photo by Margaret Stewart
While chemical controls are available, they would need to begin before symptoms appear and continue until the gall dried completely. It may be an option for the fastidious weather watcher with a good working knowledge of this disease. But, for the rest of the population, removing and destroying galls before they turn white is the best management practice to avoid having spores form and hang around until next spring. Proper pruning of the plants to improve air circulation will also reduce the chances of favorable conditions, should there be an extended cool, wet season next year.
Vegetative plant propagation is a way for one plant to create another plant without the need for pollination to occur. This process is often much faster in achieving a new plant than growing from seed. The genetics of the parent plant can be carried on through this vegetative propagation method. There are many methods to propagate plants and the one covered in this article was taught to me by my grandmother many years ago – layering. Layering is a science and an art and has been performed by humans for over four thousand years.
Propagating plants by layering can be accomplished in several ways, including simple, tip, air, mound, compound, and runner production layering methods. Many plants in nature propagate by layering accidentally when long, low-lying limbs contact the soil around the plant and are eventually covered by leaves from other surrounding trees and shrubs. This creates an organic cover over a part of the limb and keeps the area moist. This creates the situation for adventitious roots to develop at the soil contact area. This occurrence is called simple layering and is often mimicked by gardeners in the landscape. Not all plants respond to this type of propagation, but several common species that do are azaleas, jasmine, viburnum, climbing rose, and grapevines.
Unlike simple layering, tip layering involves digging out a shallow 3–4″ hole, which will allow space to bend the end of the branch down into the hole with the tip out the other side. Then, simply cover the hole to keep the branch in the ground. It may take something with a little weight placed over the covered hole to keep the branch from popping out. A brick or rock may be all that is needed. Both methods will take months for enough roots to develop before clipping the branch with a new plant ready to be dug and set somewhere new. For best results with both simple and tip layering, begin either in early spring with last seasons growth or late summer, utilizing that current year’s growth.
Simple layering. Photo Credit: Stephen Greer, University of Florida/IFAS – Santa Rosa County
Air layering is a fun adventure to rooting a new plant and can be used with both outdoor and indoor plants. It can be used on outdoor plants like camellia, azalea, maples, and magnolia, or indoor plants including weeping fig, rubber tree, and dieffenbachia. This type of layering requires a bit more planning and preparation than simple or tip layering. If the plant has a bark layer surrounding the cambium layer (this is the growing part of the limb and trunk and appears green) this area will need to be removed with a sharp clean knife. Choose a 1- ½ inch long area of the limb and scrape this area to remove the cambium layer located just beneath the bark. This is done to prevent the outside limb area from reconnecting back to the limb portion connected to the plant. Sphagnum moss will be needed to wrap around the wound site to create a rooting zone. Be sure to soak the moss with water by immersing it in a bucket of water, then squeeze it out. Wrap the moss with plastic wrap, making sure the moss is fully covered and tucked inside of the plastic. Both ends of the plastic wrap need to be secured tightly with twist ties or string. Make sure it remains tight throughout the 2 – 4 months needed for rooting to occur. If this process takes place in a sunny location, cover the plastic wrap with tin foil to block out the light.
Air layering a camelia. Photo Credit: Stephen Greer, University of Florida/IFAS – Santa Rosa County
There are other methods to layering plants and if you are interested, search online through the University of Florida IFAS EDIS site or contact your local UF IFAS Extension office in your local county. Enjoy growing your new plants.
Camellia japonica may be the quintessential Southern flowering plant, as it has decorated Southern landscapes with its giant winter flowers for over two centuries at this point. It wasn’t always that way though. The species took a long, winding road to the southern US, where it now enjoys its iconic garden status.
Camellia japonica is a native of the mountainous regions of east Asia. It was from there that “japonicas” were accidentally introduced to Europe in the late 1600s by British tea merchants, who mistook Camellia japonica for its very close cousin, the Tea Plant (Camellia sinensis). After a century-long stay in England, Camellias then made their way to America around 1800. As in England, Camellias were mostly grown as greenhouse flowering plants in the northern United States. However, in 1843, Reverend John Drayton of South Carolina, brought camellias to his home, Magnolia Plantation, and popularized them outdoors in the Charleston area. Many cultivars that are grown today trace their roots back to Rev. Drayton and Magnolia Plantation!
Camellia japonica ‘RL Wheeler’. Photo courtesy of Daniel Leonard.
Surviving every gardening fad and landscaping trend, Camellia’s popularity endures today for a couple of reasons. First is their winter flower display. Camellias provide a giant splash of color in an otherwise drab time of the year and there are literally thousands of japonica varieties in nearly every conceivable size, form, and color (provided you like white, pink, purple, and red) – there’s a camellia for everyone! Camellias are also about as low maintenance a plant as can be found in landscapes. It is not uncommon for camellias to persist in yards for generations without any help from gardeners. After the establishment phase, camellias can go decades without supplemental water, fertilizer, or pesticide applications in many cases – especially if they are sited in an ideal spot. Just plant these treasured passalong plants in a spot where water does not stand and that will receive some filtered or afternoon shade and enjoy the annual flowering show!
For more information on growing camellias, sourcing camellia plants for sale, or any other gardening topic, contact your local UF/IFAS County Extension Office. Happy gardening!
