Pruning azaleas falls under two main catagories, pruning to control growth and shape the azalea plants, and pruning to promote flowering. It is important to time the pruning of azaleas correctly to have beautiful flowering shrubs during their flowering season. Azaleas do not have to be pruned to get them to flower and in most seasons only need pruning to remove overly long stems and dead branches. There are however situations where older azaleas have become overgrown and need to be pruned back hard to regain their mound-like shape or to control their size.
There are currently four main types of azaleas bushes used for landscaping, based on their growth habits and flowering seasons. The large, evergreen, Indica azaleas put on a one time spectacular show of flowers in the early spring and can grow to a height and spread of over 15 feet depending on the azalea variety. The evergreen, dwarf and semi-dwarf Kurume and Satsuki azaleas also bloom one time in the late winter or early spring with many varieties seldom getting over 4 ft. high or wide. The newer, evergreen Encore azaleas have been bred to bloom repeatedly through the warm weather seasons and have a more open branching habit, reaching 4 to 6 ft. in height. Then there are the native, deciduous azaleas or bush honeysuckles as they are known. These slow growing, spring and early summer flowering shrubs can reach heights of 10 ft. and have a very open and upright growth habit.
Some of the better known varieties of Indica azaleas include, Fielder's white, Formosa, George Taber, Judge Solomon, and Pride of Mobile. Their large showy flower clusters are held above the dark evergreen leaves and literally cover the whole shrub for about a 1 to 2 week period in the spring. After the flowers fade and fall off, the plants will put out new growth over the next few months and then settle down for a period of rest before blooming again next spring. The flower buds for next spring will be formed on the new growth, so it is important to do any pruning before the plants are through putting on new growth. Pruning azaleas right after the flowers fade and fall away is the best time to prune all the azalea types. Waiting too long after the petals fall, beyond mid June in the lower south, will mean next years flower buds will be cut off when the branches are pruned. Because of how fast they grow, the larger Indica azaleas are best cut back well below the desired finished height. In fact they can be cut back to short 6 inch stubs and will still come back out to form nice rounded bushes by midsummer if a drastic pruning is needed.
The dwarf and semi-dwarf azaleas seldom need drastic pruning but the same timing applies to them, with any pruning being done right after they flower. Dead or diseased branches can be cut out at any time of the year. Some of the best known dwarf azalea varieties include, Gumpo Pink, Coral Bells, Christmas Cheer, Amagasi, and Gunbi. While many of these and other Kurume and Satsuki azaleas are considered dwarf varieties, there are some that will grow to 6 ft. in height.
Encore azaleas were developed to be repeat bloomers that put on flowers during the spring, summer, and fall seasons. Because they form flower buds all season long, these compact azaleas can be pruned anytime the flowers are fading except for late fall. Azaleas will react to being pruned by putting out new growth and if that new growth does not have time to harden off and mature before cold freezing weather sets in, then the plants can be damaged. Don't prune encore azaleas after mid Sept. in the deep south and hold off on pruning earlier than that in more northern areas. Springtime pruning is still the best bet even for Encore azaleas to get the best showing from them during the rest of the year. For shaping purposes, Encore azaleas are best pruned by cutting off only a few of the branches at a time and cutting them back below the level of the surrounding branches. This will leave flower buds in place for the next blooming cycle while encouraging the plant to grow more stems and get bushier.
Pruning of the Native azaleas or bush honeysuckles is again best done right after flowering but it can be quite tricky because of the more open nature of the flowering shrubs. Any cut off stubs will be more noticeable on these open airy azaleas and because they are slower growing than their asian counterparts it will take longer for them to hide any cuts made. Native azaleas should not be cut back harshly all in one season as with the evergreen azaleas. Instead cut them back gradually over a period of several years to get them to bush out and be more filled in. Only cut back up to 1/3rd of the branches in any one year thus allowing the plant to put on new growth before more is cut off. Do not prune them in the winter when they are dormant as they will have flower buds set on the branches then. The native azaleas rarely need pruning and should be allowed to take on their open airy form.
Because azaleas have hidden growth buds all along their woody branches, there are no set guidelines as to where the cuts should be made. Use good sharp pruning snips for branches under 1/4 inch and a pair of long handled loppers for larger branches. For large older bushes a chain saw may be needed. If only single branches are being cut back because they are too long or out of place, make the cut well below the length of the other surrounding branches so no ugly stub will be noticeable. Within a week a whole cluster of new growth will appear where the branch was cut. Dead or diseased branches can be cut out at anytime of the year and one of any two branches that cross and rub should be pruned away when found. Do not use hedge clipping shears to prune azaleas as this will damage too many leaves and give the plant an unnatural form. Azalea branches should vary in length for the best flower show and shape. It is best to reach down into the shrub and cut the branches off at varying lengths to get the best results when pruning azaleas.
Sometimes azaleas are pruned to form boxy formal hedges or their lower limbs are pruned away to form a more tree-like shape. Neither of these is a good plan for these flowering shrubs which when left to their own accord will form neat mounds, vase-shaped shrubs, or upright open bushes, depending on the variety. Read up on the different azalea varieties before buying azalea plants, to get those whose ultimate form and size will work in the landscape. The large growing Indica azaleas don't work well planted next to a house or in small spaces near a driveway. Likewise the small Gumpo azaleas will be lost in a large open yard when planted singly. It is important to know how to prune azaleas but it is just as important to know when not to prune them and how to use these beautiful flowering shrubs in the landscape.