Azaleas
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
Azaleas are arguably one of the most popular ornamental shrubs in the, along with our beloved hydrangeas. But with all the varieties of azaleas to choose from, people living further north can successfully grow azaleas in their gardens. (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 rhododendrons can be a better choose.
If you're wanting to ramp up your azaleas' do several following:
Practice pruning techniques and plant care
Varieties of azaleas—some blooming in early spring, some in summer
Reblooming variety, like rhododendrons.
Get blooms in the spring and then again in summer—all in one plant!
Azalea vs. Rhododendron:
What's the difference?
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.
Perhaps the easiest way to think of it is this. Azaleas are simply a specific subgroup of plants within a larger group of plants. Ones that are more generally referred to as "rhododendrons."
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. This is to help other plants shine throughout the year. You can probably find an azalea that meets almost any of your ornamental shrub design needs. This is because of the many varieties available to choose from.
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.
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.
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. This will 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. However, if you get a good deal of rain, you could give them a second boost in midsummer. Although 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.
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. This is 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.
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. Then 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. 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). Thus, your pruning efforts may not be successful.
How to Prune Azaleas
When it comes to actually pruning your azaleas, here's the key to keeping them more natural-looking. 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. 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 with 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. Here you'll 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 spring or fall. Thus 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. Since, they also kill the majority of the beneficial insects that are helping keep your pest population at bay naturally.
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 losing their leaves prematurely, consider using a fungicide spray. You should also be sure that you are practicing appropriate watering as outlined above. This is because getting the leaves wet, especially at night, can lead to mildew.