It’s difficult to think of a southern garden without envisioning azaleas graciously and vibrantly sweeping through the background. They are arguably one of the most popular ornamental shrubs in the South, along with our beloved hydrangeas. But azaleas aren’t just for Southerners to enjoy. With all the varieties of azaleas to choose from, people who live further north can successfully grow azaleas in their gardens, as well (azalea varieties range in hardiness from zones 5-9).
One of the reasons azaleas are so popular is their versatility—coming in many different shapes, sizes, and colors—some evergreen and some deciduous. That said, azaleas sometimes get a bad rap because of their short blooming season—usually about three weeks. That's why reblooming varieties like Double Shot® are such a hit.
Table of Contents:
1. What's the difference between azaleas and rhododendrons?
2. How to use azaleas in garden design
3. When, where, and how to plant
4. How to water, mulch, and fertilize
5. When, why, and how to prune
6. Common azalea challenges (including azalea lace bugs)
7. Best easy-care azaleas
If you’re wanting to ramp up your azaleas’ flower power or just enjoy them for their other attributes, you can do several things:
- Practice appropriate pruning techniques and plant care.
- Plant several varieties of azaleas in different areas of your garden—some blooming in early spring, some in summer.
- Consider planting a reblooming variety, like Monrovia’s exclusive Double Shot® Azaleas, to get blooms in the spring and then again in summer—all in one plant!
To that end, this guide covers a number of helpful topics that will hopefully help you grow azaleas in your garden with greater confidence. Do you have your own tip to share? Please let us know on social media @MonroviaPlants.
1. Azalea vs. Rhododendron: What's the difference?
What's the difference between azaleas and rhododendrons?
Sometimes people get confused about the difference between an azalea and a rhododendron. That’s because an azalea is always a rhododendron, but a rhododendron is not necessarily an azalea. The confusion really lies with how they are named—specifically, their common names.
All the plants that are commonly known as "azaleas" or "rhododendrons" are members of the genus Rhododendron, so they all have “rhododendron” in their scientific name. Under that, there are eight subgenera, comprised of almost 1,000 species and almost 20,000 hybrids of Rhododendron. Those that have an azalea common name are found in two of those subgenera.
Perhaps the easiest way to think of it is that azaleas are simply a specific subgroup of plants within a larger group of plants that are more generally referred to as "rhododendrons."
If you’re trying to distinguish an azalea from a rhododendron in your garden, you can look for the following characteristics:
- Rhododendrons are always evergreen, whereas azaleas can be either evergreen or deciduous (i.e., lose their leaves).
- Almost everything about a rhododendron is typically bigger—their overall size, flowers, and leaves. Their leaves also tend to be glossier and thicker, almost leather-like.
- Azaleas tend to be small to medium-sized shrubs with many, smaller stems, while rhododendrons typically have fewer, sturdier stems.
- Azaleas usually have smaller, funnel-shaped flowers, while rhododendrons’ larger flowers are more bell-shaped.
- Although azaleas tend to bloom earlier, both rhododendrons and azaleas typically bloom in the spring, with some varieties blooming into summer and fall in some locations and climates. As noted above, double-blooming azaleas, like Double Shot® Azaleas, bloom in spring and then again in the summer.
There are a number of other subtle, more scientific differences that botanists may mention, but the list above should help you get started telling one from the other.
Note: For the purposes of this guide, we're focusing on evergreen azaleas because they are one of the most common azaleas in garden design.
2. How to use azaleas in garden design
Azaleas are really a utility player in the garden. They provide both striking beauty when they are in bloom as well as a very reliable evergreen backdrop to help other plants shine throughout the year. Because of the many varieties available to choose from, you can probably find an azalea that meets almost any of your ornamental shrub design needs.
Larger varieties of azaleas are best used where they have room to grow. They make a great choice along the perimeter of your yard or as the backbone of your larger beds. Although they look great when they are planted alone, sweeps of medium-sized varieties are an excellent option to create naturalized islands of shrubs—allowing you to see above and beyond them. Compact varieties can be used as borders, along paths, and in containers.
5 Ways to use azaleas in your garden
1. En masse
Drifts of azaleas can "hug" a yard and direct your eye from one space to another, naturally connecting them together. Their mounding form makes them ideal candidates for massing in shrub borders and perennial beds.
Evergreen azaleas like Double Shot® Azaleas make for great hedges thanks to their dense growth habit and evergreen leaves. The pop of color adds a layer of excitement twice a year, too.
3. Foundation Plants
You might notice that azaleas are often used as foundation plants (planted next to the foundation of the home) because they are the perfect size and shape to fill the role. They also look great in the full- to part-shade conditions that you often have right next to the house. Plus, the bright flowers look gorgeous against a wall of any color.
4. Container Specimens
Compact azaleas (like Double Shot®) are perfect for containers and are great for adding a pop of color to patios, porches, and outdoor rooms.
5. Garden Specimens
Use a single azalea shrub to punctuate and anchor a smaller garden bed. There are so many forms and colors to choose from, you can combine them with just about anything in the garden and make a beautiful impact.
3. Where, when, and how to plant azaleas
Azaleas are an extremely hardy shrub. In fact, I include them on my list of “bullet-proof plants” when talking to clients. But there are certainly things you can do to ensure a happier and healthier plant. Here are a few things to keep in mind from the get-go.
Where to plant azaleas
As with all plants, the phrase “location, location, location” certainly applies to azaleas. For the most part they prefer partial shade or dappled sunlight, with morning sun always being the best. If they get too much sun, they will struggle from all the exposure. But if they get too little sun, you may have a healthy-looking plant, but not so many flowers.
- Azaleas are great for containers, just be sure to choose a larger-sized container to allow room for their robust growth.
- Azaleas prefer moist, well-drained soil, as their shallow roots don’t like sitting in water.
- Azaleas also prefer soil that’s on the acidic side of the pH scale (pH of 4.5 to 6.0). People who have naturally acidic soil will be able to grow azaleas quite easily. However, if you have more neutral to alkaline soil, you will need to amend the soil. Aluminum sulfate, sulfur, acidic fertilizer, and iron sulfate are all commonly used to make the soil more acidic. You can also use coffee grounds, pine needle mulch, and sphagnum peat moss as more gentle forms of acidifying soil.
When to plant azaleas
In milder regions, you can plant azaleas almost any time of year. But the best time is the spring or fall, when the temperatures aren’t too hot or too cold. Planting in fall is truly ideal because it gives them a chance to put down roots to better support the new growth and flowers in the spring.
How to plant azaleas
When planting azaleas, dig a hole about the same depth of the container and about 2-3 times as wide. Make sure to leave the top of the root ball just above the grade of the soil. Doing both will encourage the right kind of root growth. Then topdress with compost and mulch to give them some nutrients over time.
4. How to water, mulch, and fertilize azaleas
Once you have your azaleas in the ground make sure to give them what they need to thrive going forward.
How to Water Azaleas
When watering azaleas, aim toward the base. That way you will minimize getting water on their leaves; and, therefore, mitigate the chances of disease. The best time to water is always in the morning, giving the sun time to dry off whatever water lands on their leaves.
How to Mulch Azaleas
Think “2 and 2” when mulching azaleas— 2 inches of mulch, 2 inches away from the trunk. This deters critters from munching on them. Acidic mulches, like pine straw, pine bark, and chopped oak leaves are best. As the mulch breaks down, it will give them the nutrients they love. Replenish the mulch every year or as needed.
How to Fertilize Azaleas
The best time to fertilize azaleas is in the spring, right after they are done showing off their beautiful flowers. That may be enough, but if you get a good deal of rain, you could give them a second boost in midsummer, but not too late into the summer when the sun is scorching. Acidic fertilizer is probably best, especially if your soil isn't truly acidic to begin with.
5. When, why, and how to prune azaleas
If you’re looking to keep your azaleas their happiest … and you too (i.e., more flowers and less maintenance), it’s critical to understand when, why, and how to prune them.
When to prune azaleas
For the most part, azaleas bloom on “old wood”. That simply means that they set their blooms for next year on this year’s growth. So it’s recommended that you prune your azaleas within three weeks of when they are done blooming. This will give them enough time to produce flower buds for next year’s bloom. Next spring won’t be as colorful if you wait much longer.
Note: Double-blooming azaleas, like Double Shot® Azaleas, bloom on both old and new wood. So if you miss the ideal window to prune the old wood you may have fewer blooms in the spring, but you’ll still have the blooms in the summer on the new growth.
Why prune azaleas
- Dead, damaged, or diseased branches: Removing dead, damaged, or diseased branches can be done anytime. Dead branches should be cut back to a branch point that’s alive so that dormant buds can send out new growth. Damaged or broken branches should be cut back to just above a dormant bud for the same reason. Diseased branches should be cut back well beyond the diseased area and disposed of far, far away. And while you’re at it, although they’re potentially healthy, go ahead and take the opportunity to cut crossing branches. This will improve air circulation and decrease the potential for disease.
- Shaping things up: There’s a good bit of both art and science when it comes to shaping up your azaleas. And how you shape things up comes down to personal preference.
I prefer keeping azaleas in their natural, more airy habit, and I think they do, too. That said, the first thing you want to make sure to do has nothing to do with pruning, but everything to do with choosing the right plant for the right space. In other words, you don’t want to plant a large azalea in front of a low window or right next to a sidewalk. Otherwise, you’ll have to prune things back to clear your views and/or passage, thereby creating a not-so-natural-looking azalea. So choose wisely. And if you do, you’ll not only get a more natural-looking azalea, but you’ll minimize your pruning efforts as well. Win-win!
If you like a more structured look (i.e., less natural), azaleas can be sheared into more regular shapes, like a formal hedge. That’s best done once a year just after flowering. However, when you prune azaleas this way you will encourage leaves (and flowers) to grow only at the top couple of inches of the plant. This dense layer of foliage blocks the sun from reaching the interior, thereby shading out any leaf growth below. This is especially problematic if a section dies off or you’re needing to lower your azaleas down a bit because you would be left staring at what looks like a dead interior.
- Rejuvenating: As azaleas age, they can become very leggy. To help restore and reinvigorate these older shrubs you’ll need to consider taking more drastic measures and cut them way back. This is referred to as rejuvenation or renewal pruning. But rest assured, one of the great things about azaleas is that they are so hardy that they can take almost anything you throw their way. That said, some really old shrubs may be too far gone (i.e., a third of the branches have no leaves), so your pruning efforts may not be successful.
How to Prune Azaleas
When it comes to actually pruning your azaleas, the key to keeping them more natural-looking is to reach into the interior to cut stems at varying heights, in somewhat of a “W” pattern. Each time make sure to cut at a branch point. Doing so will allow the sun to shine into the interior, allowing them to keep their “cloudlike” appearance. From time to time, step back to see how things look … and then go back in until you are pleased with your handiwork.
6. Common Azalea Questions or Challenges
You shouldn’t have many problems if you care for your azaleas as outlined above. They are extremely hardy and easy to take care of. However, as with all plants, you could run into a number of problems or have some questions about their health. The questions that my clients ask me about most are outlined below.
Why are my azalea's leaves turning yellow?
Almost every fall I hear from friends and clients worried about their azaleas’ leaves turning bright yellow. The good news is they are probably just molting (or losing their leaves naturally). Although they are always green, evergreen shrubs do lose their leaves, it’s just not all at once like deciduous plants do. Azaleas set their leaf buds in the fall and the emergence of these buds prompts molting. There’s nothing you need to do or worry about. It’s supposed to happen.
However, there are a couple of other reasons why your azalea's leaves could be turning yellow. But again, there’s not much to worry about, they are both very treatable. The first one is covered below, azalea lace bugs. The other reason is a nutrient deficiency, likely nitrogen or iron. If that’s potentially the case, just make sure that there’s proper drainage and then topdress them with organic matter. Testing your soil will be the best way to see if nutrient deficiency is the issue. If the problem persists, hit them with a general-purpose fertilizer (or one that’s tailored for azaleas) in the spring.
Why are my azalea's leaves turning white?
Two of the most common threats to azaleas are azalea lace bugs and powdery mildew. Get detailed information about how to tell what's ailing your azaleas below.
How can I tell if my azaleas have lace bugs?
Azaleas that have speckled, whitish, or light yellow leaves that look like the leaves pictured here probably have azalea lace bugs.
To determine if that’s what’s ailing your azaleas, look at the underside of the leaves to see if there is what entomologists call "frass," a.k.a. bug poop.
If your leaves are speckled and have frass on the undersides, you can use insecticidal soap in the spring or fall, making sure to soak the underside of the leaves. If you want in-depth information about these azalea pests, check out this presentation by Robin Rosetta of Oregon State University.
For gardeners, systemic insecticides should always be the last-resort option, as they also kill the majority of the beneficial insects that are helping keep your pest population at bay naturally.
Azalea lace bug and azalea lace bug leaf damage photos above by courtesy of Oregon Department of Agriculture, Image by Thomas Shahan, IPPM Imaging
How can I tell if my azaleas have powdery mildew?
If your azaleas have what looks like a white powdery growth on their leaves, they may have powdery mildew. If so, and you want to mitigate the chances of their losing their leaves prematurely, you may consider using a fungicide spray. You should also be sure that you are practicing appropriate watering as outlined above, because getting the leaves wet, especially at night, can lead to mildew.
7. Best Easy-Care Azaleas: Double Shot® Azaleas (Zones 6-9)
Are you looking for a hardy, compact azalea that blooms not once, but twice a year? If so, try adding Monrovia’s exclusive Double Shot® Azaleas to your garden. Growing about 3’ tall and wide, this vigorous, rounded evergreen beauty can serve as the perfect border, informal hedge, or even as a great container accent. Being more heat and cold tolerant than many other azaleas, Double Shot® Azaleas make an easy choice for any gardener to include in their garden. And the bonus is, as a reblooming azalea, they show off their large flowers in both spring and summer. What’s not to love?
About the Author and Designer
Doug Scott is the owner and lead designer at Redeem Your Ground, an exterior design firm, based in Atlanta, GA. Through his designs, Doug hopes to create outdoor spaces that reflect how each of his clients wants to live outside at home. Doug and his wife, Brittany, also have a family, home & garden blog by the same name, where they share stories, helpful information, and instructional how-to’s—hoping to enable and inspire others to live more fully at home.