Azalea Care: How to Grow Azaleas in Your Home Garden

Did you know that azaleas are actually rhododendrons? As The Plant Book, edited by Susan Page and Margaret Olds, states: “There are three main categories of rhododendrons, namely: azaleas (deciduous and evergreen); tropical or vireya rhododendrons; and the temperate plants we might call ‘true rhododendrons’.” The leaves of azalea shrubs might be narrower than the often large and leathery leaves of a ‘true’ rhododendron shrub. But like “Rhodia,” azaleas trumpet their virtues with showy, often horn-shaped blooms that appear in spring or early summer, with a repeat in fall for encore types.

Although rhododendron care is similar, this article will look specifically at azalea care. So read on to learn everything you need to know about growing azaleas.

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Growing azaleas at a glance

common names: Azalea
Scientific name: Rhododendron spp.
hardening zone: USDA Zones 4 through 12
floor: Well draining, pH 4.5 to 6
light: Light shade or partial sun
water: Constantly wet
meal: Fertilizer for acid-loving plants
propagation: stratification
security: Poisonous

azalea Characteristics

According to the Azalea Society of America, azaleas can vary in height from a 1-foot dwarf variety to a 10-foot azalea tree. They come in both deciduous and evergreen varieties, the latter being generally smaller. But even these aren’t entirely evergreen, as they shed their spring foliage in the fall but cling to their leathery summer foliage through the winter.

Deciduous azaleas can often be grown in full sun in the north, where they will take on correspondingly sunnier hues such as yellow and orange, while evergreen species generally do not tolerate as much light. Deciduous varieties are usually more robust than evergreens. Azalea flowers, occasionally fragrant, vary in diameter from 1/4 inch to 5 inches and come in almost every shade except true blue. Consider planting endangered species like the Flame Azalea.

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Recommended azalea varieties

• encore: As the series name – and the “fall” in many cultivar names – would suggest, these azaleas bloom a second time in the fall in USDA zones 5 through 10.
• Gent: An early variety of deciduous azaleas, these ancient azalea species tend to grow tall and bloom late with small, often sweetly scented flowers in USDA zones 6 through 9.
• indica: The original evergreen houseplant azaleas, classic ‘Indica’ types, are only hardy to USDA zones 8 through 11 and rarely exceed 2 feet tall, but they produce some of the most elaborate blooms.
• Knap Hill: Descended from ‘Gent’ azalea species, these deciduous hybrids would later produce cultivars ‘Exbury’ and ‘Ilam’ – most with single flowers on large bushes in USDA Zones 5 through 9.
• curume: Kurume azaleas enhance the hardiness of evergreen azaleas and can thrive in USDA zones 6 through 9, offering compact bushes with small flowers, often with a semi-double (tube-in-tube) appearance.

Plant azaleas

When planting azaleas, keep in mind that their fine, shallow roots don’t do well in rocky or compacted soil.

When is the best time to plant azaleas?

Plant your azaleas in late spring or early fall. If your soil is very heavy, build an 8-inch to 1-foot raised bed on top, filled with 2 parts ground pine bark or oak leaf compost combined with 1 part coarse sand and 1 part garden soil.

Where Can Azaleas Grow?

For your azalea garden, choose a site with well-drained soil with a pH between 4.5 and 6, protected from south and west winds by buildings or other plants. The location should receive only light shade, dappled sun, or morning sun. Avoid planting azaleas near cement, which raises soil pH, or on windswept corners of buildings.

How do you plant azaleas?

The depth at which you plant your azalea should depend on the type of soil you have. Follow these instructions when planting azaleas:

1. Dig a hole three times the width of your azalea’s root ball.
2. If your soil is mostly clay, make the hole shallow enough so that the top of the root ball is 4 inches off the ground, 2 inches off the ground for average garden loam.
3. Plant the azalea in sandy soil with the top of its root ball level with the surrounding soil.
4. Space the plants 3 to 4 feet apart.

Can you grow azaleas in containers?

Because of their shallow root system, azaleas grow well in containers and are often sold in pots as gift plants – especially around Easter. However, keep in mind that “floristic” azalea species are generally descended from Rhododendron simsiiwhich are only hardy in USDA zones 8 through 11. If planted in lower zones in the garden, they are unlikely to survive.

They can be difficult houseplants, but growing them indoors isn’t impossible when you consider azalea preferences. See “Preparing Azaleas for Winter” below.

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water azaleas

Azaleas should receive at least one inch of rainwater per week or equivalent, preferably via a drip hose or drip irrigation. While you should never allow the root balls of plants to dry out completely, remember that moisture can cause root rot in azaleas. For this reason, it’s a good idea to add several inches of organic mulch, such as pine straw or chopped bark, to azalea beds to maintain moisture without overwatering.

The soil of a potted azalea plant should also be kept slightly moist at all times. If possible, use rain or spring water so that hard tap water does not sweeten the soil.

Fertilize azaleas

These shrubs can generally get most of the nutrients they need from their soil. However, you may want to lightly feed them a few times a year, in spring and early summer using an acidic organic fertilizer such as 4-3-4. However, never feed them after midsummer. If you want to grow azaleas in soil that isn’t acidic enough, you may need to apply sulfur or ferrous sulfate to that soil a few months in advance to “acidify” it.

Only fertilize houseplant azaleas in the summer, following the directions on the container. Opt for a water-soluble food for acid-loving plants that contains iron.

clipping azaleas

Azaleas do not require the removal of faded inflorescences like true rhododendrons do. However, if you do want to prune your azalea bush a bit, do so shortly after the plant has flowered – before the month of July.

If it has become so old and scrawny that you prefer a more drastic regeneration, prune the azalea back to 6 to 12 inches from the ground in spring, bearing in mind that such pruning will kill all blooms that year. Once new shoots are a foot tall, pinch out their tips to force them to branch out.

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propagate azaleas

Probably the easiest way to propagate an azalea is by layering. To try this, bend a branch onto the ground without detaching it from the bush. Scrape a little bark off this branch and soak the debarked area with rooting hormone before pinning it in a shallow trench and covering with an inch or two of soil. The part of the branch that is underground should root within a year, after which it can be detached from its parent bush.

safety aspects

All rhododendrons, including azaleas, are extremely toxic to humans, animals, and fish. However, livestock – particularly sheep and goats – are more likely to graze on them than your children or pets. For this reason, you should keep the bushes away from pastures and, of course, from fish ponds.

Symptoms of poisoning in animals and humans can include vomiting, drooling, and diarrhea, as well as weakness and paralysis. Keep in mind that nectar from rhododendrons can also make honey toxic.

Possible pests and diseases

Root rot in azaleas causes wilting that resembles that of a drought, but it actually indicates that too much water has rotted the roots. In this case, there is little hope of saving the plant.

Chlorosis, in which the leaves of an azalea bush are yellow with green veins, generally indicates the soil is too alkaline, preventing the absorption of minerals like iron or manganese. You can acidify the soil with ferrous sulfate, but it can take months to absorb. For a quicker — but temporary — fix, spray iron or manganese chelates directly onto the leaves.

Prepare azaleas for winter

If you want to get a houseplant azalea to bloom again, leave it in late fall until it has experienced 6 to 8 weeks of overnight temperatures between 40 and 50 degrees Fahrenheit. Bring indoors before temperatures drop below freezing and place on a moisture tray in a cool, airy spot where it will receive bright indirect light and temperatures between 60 and 75 degrees.

Should your azaleas be planted outdoors in a wind-protected position—as described in “Planting Azaleas” above—and mulched with 2 to 3 inches of shredded bark, they likely won’t need additional shelter to stay evergreen.

Looking for more flowering shrubs? Check out our installation guides butterfly bush, hibiscusand Shrubs that thrive in full sun.