Azaleas come in thousands of varieties and can grow to be 10 feet tall or dwarf varieties that only reach a foot or two. Here’s how to pick the right one for your garden and what you can do to help it reach its full potential.
Garden catalogs will tell you how tall and wide the shrub will grow in 10 years under ideal conditions. Choose a plant that will eventually fill the space you’ve designated for it. This reduces the need for pruning as well as transplanting!
According to the Azalea Society of America, there are over 10,000 named varieties, so picking the right one for your garden can be a daunting task! A good neighborhood garden center should have the varieties that will thrive in your area, but doing some preliminary research is highly recommended.
Azalea Growth Rate
These shrubs typically grow at a rate of less than 12 inches per year. As they get older, the rate at which their foliage and height grow slows down. Plants in their immature or juvenile stages grow faster than those in their maturing or mature stages.
It is critical to provide them with ideal conditions for them to grow at their full potential. Soil quality, pH, fertilizer application, and environmental stress all play a role. It’s critical to have well-drained, organically rich landscape beds. Plants grown in the shade frequently grow taller because they are “reaching” for the sun.
How big do they grow? Here are some general guidelines to follow.
All deciduous azaleas are native to North America. They are classified into three groups, which include both native and hybrid species:
- The white group grows 4 to 5 feet tall
- The pink group gets 6 to 8 feet tall
- The orange group, the tallest at 8 to10 feet tall
Azaleas that are evergreen are native to Japan. They are classified into two types: species and hybrids. Among the species groups are:
- The Indica and Indian groups, which generally get 6 to 10 feet tall
- The Kyushu group that top out at about 3 feet
Hybrid Groups include:
- The Satsuki group, which are 1 to 3 feet tall
- The Encore® Group grows 2.5 to 3 feet tall
- The Glenn Dale that are 4 to 6 feet tall
All varieties will only grow to a predetermined genetic size. A cultivar that has been bred to grow to 3 feet tall will not grow any taller. And some varieties grow at a faster rate than others. Some can grow up to a foot per year, while others only an inch or two. However, there are some things you can do to help your azalea grow to its full potential:
- Be sure it is hardy in your zone.
- Plant in the appropriate location. Most prefer dappled sun or morning sun with afternoon shade, but some varieties can tolerate more sun. None of them thrive in complete shade.
- Verify that the soil conditions are suitable. These shrubs require acidic soil with a pH of 4.5 to 6. Loamy, well-draining soil is also required.
- Spread a little mulch to mimic the forest floor after planting to help your new shrub feel at home. A mulch layer of 2 to 3 inches around your shrub provides nutrients, regulates soil temperatures, and suppresses weed seeds. Make sure to mulch established plants as well.
- Water your shrubs regularly. They require about 1 inch of water per week, which can be obtained from rain or supplemental watering.
- It’s not necessary to use fertilizer. They thrive in the absence of any fertilizer.
Different Varieties to Consider
Let’s take a look at just a few of the many, many options available. Here is a selection of popular favorites that will help you understand the size range, color spectrum, and hardiness level you can expect to find when you start shopping.
In the winter, deciduous varieties lose their leaves. Many have stunning red or burgundy fall foliage. Here are a few of our favorites:
- ‘Karen’ is hardy from zone 4 to zone 9. The flowers are purpley-pink, and the leaves turn burgundy in the fall. Grows 2 to 4 feet tall and 3 to 5 feet wide.
- ‘Northern Hi-Lights’ is a University of Minnesota introduction, so you know it’s tough! It grows 4 to 8 feet tall and 4.5 feet wide and is hardy in zones 4 to 8. It has white flowers with yellow splotches and leaves that turn burgundy in the fall.
- Flame (Rhododendron calendulaceum) grows well in zones 5–8. This native shrub can reach heights of 6 to 12 feet and widths of 4 to 8 feet. Orange, red, yellow, gold, and apricot are the flower colors. Once established, it tolerates dry soils.
- Western azalea (Rhododendron occidentale) is native to the west coast of the United States and is hardy in zones 8 to 9. It can grow to be 5 to 10 feet tall. It blooms from mid to late spring, with fragrant flowers that can be pink, white, yellow, or tricolor.
- Rhododendron arborescens can reach heights of 8 to 12 feet and has a spread of 8 to 12 feet. It is hardy in zones 4–8, and it can tolerate full sun in cooler climates. In the autumn, the leaves turn red to purple.
In the winter, evergreen varieties do not lose their leaves. They are best suited to areas with mild winters, though they can tolerate a few frosty nights.
- Rhododendron ‘Ginny Gee’ is a dwarf variety that grows only 1 to 2 feet tall and wide. It is hardy in zones 6–8 and, once established, can withstand colder nights, drought, and heat. The flowers are white with pink edges, and the leaves turn a reddish color in the winter.
- Gumpo White is a hybrid Sutsuki that grows to be 2 feet tall and 3 feet wide. Because of its small size, it is ideal for growing in a container. It blooms in late spring and early summer and is hardy in zones 6–9.
- The Indian Azalea (Rhododendron simsii) blooms continuously from late winter to late summer. It is hardy in zones 8 to 11 but can withstand a few frosty nights, making it an excellent choice for western and southern gardens. With a height of 18 to 24 inches and a width of 15 to 18 inches, it can be grown in a pot and brought indoors for the winter if your winters are cold. There are numerous color options, including pinks, reds, coral, purples, and white.
- Azalea indica ‘Happy Days’ is hardy in zones 9 to 11. This is yet another variety that is suitable for the southern states and California. It can reach heights of 3 to 5 feet and widths of 4 to 6 feet. This shrub bears a large number of violet to purple double flowers.
- Autumn Belle is an Encore® series cultivar that has been bred for repeat blooming. It grows to 3 to 4 feet high and wide and is hardy in zones 7 to 9. The flowers are light pink. Encore® azaleas are available in over 30 varieties and various colors. If you live in an area with very cold winters, you can grow them indoors in the winter and then move them outside once the danger of frost has passed.
Creating A Hedge
Nothing beats an azalea hedge for a spectacular spring flower display! If the conditions are right, this type of hedge is a lovely, low-maintenance option. These shrubs can also be used as a privacy hedge.
Why would you want to grow an azalea hedge? Their spring beauty is unrivaled, and some cultivars will also bloom into the summer. There are numerous flower colors to choose from, many of which are fragrant. You can also “mix and match” sizes and bloom colors to increase the wow factor.
An evergreen azalea hedge is a lovely privacy hedge, but you won’t have that privacy in the winter if you use deciduous varieties. Because the shrubs require airflow, they should not be planted too close together. Choose evergreens such as arborvitae or yews if you want a dense, year-round privacy hedge.
Azaleas might not be the best choice if you want a formal hedge. Shearing the shrubs may result in the loss of next year’s flowers. Azaleas could be the perfect choice if you want to go for a more natural look.
These beauties can also be used to make a mixed border. For a four-season hedge, combine needled evergreens, other spring bloomers like forsythia or dogwood, summer-blooming shrubs, and shrubs with great fall colors like aronia.
If you consider the mature size of the azalea before planting, you’ll discover that pruning isn’t really necessary. There may be the odd dead, broken, or stray branch that needs to be trimmed, but that should be the extent of your shrub’s pruning.
If you inherited an oversized azalea when you moved in, pruning may be required to shorten the shrub’s height and shape it. They have shallow roots and are simple to dig up and transplant if necessary. Make sure you have the muscle to move it, especially if it’s an older specimen!
If you must prune, wait until the shrub has finished flowering before doing so. They set their flower buds for the following year in the previous summer, so pruning them later in the year removes next spring’s flowers.