Azaleas: Issues and Care
Article By: Jessica Warren, ANR Agent, Camden Co.
Azaleas are one of the most quintessentially Southern plants. This is a bit ironic considering that the azaleas most people love and associate with the South are actually from Asia. Whether it’s evergreen hybrids from Asia, or deciduous and fragrant native azaleas – most people have questions about azaleas and their care. Today we’ll cover some of the most common issues that may affect your azaleas.
The first step for a healthy plant of any type is planting it correctly and choosing the right site for it. Azaleas should be planted in a hole 2-3 times wider than the root ball and no deeper than the root ball. Azaleas are shallow rooted and planting too deep can be lethal. Do not fertilize at planting as this can dehydrate and injure sensitive roots. Azaleas prefer filtered shade and moist, well-drained soil. They will not survive in wet, poorly drained soils. Overwatering and poor drainage are the primary azalea issues that I see in the county. Avoid planting azaleas near sidewalks, driveways, and other surfaces that may radiate heat. Azaleas prefer acidic soils with a pH of 4.5-6.0. Levels above 6.0 (which are extremely common here) can cause nutrient deficiency. To be clear, this cannot be corrected with more fertilizer. When pH levels are too high for a plant it cannot absorb the nutrients that are available in the soil.
After planting, a few key areas of maintenance are important. Mulching your azaleas after planting will help conserve water in the soil, insulate roots against summer heat and winter cold, discourage weeds, and build the organic matter in the soil that azaleas need. Mulch should be replenished over time to maintain a 3-5 inch layer, but old mulch should not be removed unless there is a disease issue (again the old mulch breaks down into organic matter for the soil). As with all plants, the mulch should be pulled away 1-2 inches from the stem/trunk to prevent rot and other issues. Pine straw, shredded pine bark, or fallen leaves make the best mulch for azaleas. Before watering, pull back the mulch and check the soil moisture level to see if watering is necessary. Drip irrigation or soaker hoses are the best way to water, as overhead irrigation encourages foliar diseases. It is best to water in the early morning. Azaleas are easily injured by excess fertilization and can usually obtain the nutrients they need from the soil and decomposing mulch. It is important to get a soil test before fertilizing azaleas to see if fertilization is warranted. If it is necessary to fertilize, it’s best to do it just after flowering and when foliage is dry. Do not remove or pull back mulch when fertilizing.
Pruning is a maintenance topic that always evokes a lot of questions. Pruning is not always necessary and should only be done with a purpose (reduce size, increase airflow, remove deadwood and crossing branches, etc.). The best time to prune azaleas is after they bloom. Avoid pruning spring blooming azaleas after July 1st. Azaleas may be pruned to within 6-12 inches of ground level if necessary. As with most plants, thinning is preferred to heading as a pruning technique and is healthier for the plant. Thinning is the removal of select branches back to a crotch while heading is chopping things off at the top (hedging, shearing, etc.).
Many azalea problems are caused by cultural or environmental problems such as overwatering, poorly drained soils, improper soil pH, and improper planting techniques or location. Leaf chlorosis is yellowing of the leaves, usually with dark green leaf veins. This can be caused by overwatering/poor drainage, nutrient deficiency, overfertilization, or high soil pH. Poor drainage can cause not only leaf chlorosis, but also small yellow leaves, stunted growth, wilting, bronzing and leaf scorch. Leaf scorch is the death of leaf tissue along the margins and can also be caused by overfertilization, drought stress, and a broadcast application of fertilizer when the foliage is wet. Another environmental issue azaleas face is cold injury. Cold injury can show up as browning of the leaves, leaf drop, bark splitting, and bud abortion.
Azaleas aren’t heavily threatened by insect pests, but they can have issues from time to time. Pests include azalea lace bugs, azalea caterpillar, azalea bark scale, Southern red mite, and azalea leafminer. Most of these pests are controlled by beneficial predatory insects and cause little threat to the health of the plant. Some of these pests, such as the azalea caterpillar, also serve as food for nesting songbird chicks.
There are several diseases that can affect azaleas. In order for disease to develop, three factors have to be present at the same time: a susceptible host, the pathogen (which is usually naturally present in the environment), and an environment that favors disease. In order to control disease, at least one of these factors must be removed. Most azalea diseases are caused by fungal pathogens and occur due to improper or excessive watering, improper growing habits, or weather conditions. Management of most azalea diseases requires the same steps: avoiding overhead irrigation, pruning out infected areas (if reasonable), removing debris from under/around the plant and disposing of it in bagged garbage to stop the spread.
As with anything in the landscape, you want to properly diagnose an azalea issue before applying any kind of treatment. If you have questions, send me a couple of clear photos of the issue and I can help you with diagnosis and a treatment strategy.