Caring for Azaleas in Pots and Containers Outdoors

Azaleas are one of the most beautiful shrubs of all garden plants and grow, flower, and thrive in pots for over 100 years. Azaleas require acidic soils, with good drainage and moisture retention so pots and containers are a great option if you have slow-draining or alkaline soils. Azaleas also require partial shade so planting in pots allows you to move the plant to find the optimal balance of sun (for strong blooms) and shade (to protect the tender leaves).

Caring for azaleas in pots outdoors quick guide:

Keep reading to learn all the best practices to ensure your azaleas flower beautifully every year and live for over 100 years…

Preparing Potting Soil for Azaleas

Azaleas require potting soil that has the following characteristics:

• Well-draining to reduce the chance of fungal disease root rot
• Moisture retentive to allow consistent moisture so the roots do not dry out
• Well-aerated soil with a friable texture and porous structure.
• Acidic soil pH of between 4-6.
• Nutrient rich soil with plenty of organic matter.

Azaleas require a balance of soil that retains moisture effectively but also has a structure that allows excess water to drain away so that the soil does not become boggy as this would encourage root rot.

The way to achieve this is with soil that has a high organic content. 1/3 Compost or leaf mold 1/3 peat moss (or ericaceous compost) and 1/3 well-rotted manure provide all the soil characteristics that a potted azalea requires and will ensure healthy growth.

Compost and leaf mold retain moisture and create a well-draining structure whereas the peat moss provides the right acidic soil pH. Azaleas require acidic soil to be able to take up nutrients from the soil and they will exhibit signs of stress (such as yellow leaves) in soil that is closer to neutral (pH 7) or alkaline soils.

If you do not have access to peat moss then ericaceous soil is available online and garden stores will ensure that your azalea has the correct soil pH.

Well-rotted manure will provide a nutrient hit for the azalea roots and help to retain moisture, but it can be substituted for compost or leaf mold if necessary.

I would also recommend that you use a layer of gravel at the bottom of the pot so that water flows efficiently out of the base. This will help to avoid compacted soil slowing down the drainage.

If you consider planting azaleas in the garden read my article, preparing garden soil for azaleas.

Water Frequently to Keep the Soil Moist

One of the key requirements when caring for azaleas is that the soil should be consistently moist but not saturated. Azaleas have shallow roots so they are often the first plants in the garden to show signs of drought.

Pots also tend to dry out quicker than garden soil so careful watering is important. Always water azaleas generously so that water infiltrates the soil and trickles out of the base of the pot.

Specifically how often to water potted azaleas varies according to climate, weather, and maturity of the plant so I have made a table to summarise how to often water your potted azalea according to the conditions:

To learn more read my article on how much and how often to water azaleas.

Slow Release Fertilizer in Spring

Azaleas are not especially heavy feeders and plants that are in nutrient rich garden soil can thrive without additional fertilizer.

However potted azaleas require a fertilizer to grow and flower to their best as there is a limited capacity for nutrients in potted soil and they do not benefit from the soil ecosystem to the same extent as azaleas planted in garden boarders.

The best fertilizer for azaleas in pots is slow-release granules that are specifically formulated for azaleas (such as Miracle Grow).

The granules are easy to apply and contain the right balance of nutrients that azaleas require therefore there is no risk of over-fertilizing in the plant which can damage the roots. They also contribute to maintaining the optimal acidic soil pH which helps to ensure nutrient uptake.

Apply fertilizer in the Spring as soon as you see new foliage growth and with slow-release granules you only have to apply once per year. Do not apply fertilizer in late Summer as this may encourage foliage growth at the expense of flowers and can stimulate new growth that is more vulnerable to upcoming Winter frost.

Fertilizing ensures healthy green leaves and promotes strong blooms so that the plant remains resistant to disease and can potentially live for more than 100 years.

Choosing the Right Pot for Azaleas

Azaleas can be grown in different types of pots and containers as long as it has drainage holes in the base. Ideally, pots should be around 16 inches in diameter with clay or terracotta material.

You can grow azaleas in smaller pots initially but it is likely that you will have to re-pot the plant after a couple of years. A 16-inch pot contains enough soil to hold moisture and more soil helps to insulate the roots in Winter.

Soil in pots tends to heat up quickly in the sun which increases soil evaporation and the chance of drought. Clay or terracotta pots tend to be thicker than plastic or metal containers and therefore the soil does not heat up as quickly in the sun which helps to maintain soil moisture.

Light Requirements for Flowering

Azaleas prefer partial shade and dappled light with around 4 hours of sun per day (depending on the climate). In cooler temperate climates with more rainfall and overcast days (such as Scotland or Washington in the USA) an azalea can take full sun.

However in arid climates (such as California or Southern Europe) with intense sunshine the leaves of the azalea are susceptible to sunburn, flowers tend to wilt and the risk of drought is substantially increased. In these climates about four hours of morning sun with protection from the midday sun is ideal.

Azalea can grow in full shade but sunlight helps to stimulate the formation of flowers and can encourage better growth.

The great thing about growing azaleas in pots is that you can move the azalea around until you have found the optimal balance of sun and shade.

The goal is to find an area with enough protection from the wind, frost, and midday sun, without shading the azalea to the extent that flowering could be negatively affected.

If the azalea is producing few flowers then move it to an area with more sun and if the azalea has scorched leaves it will require more hours of shade.

Dappled light under a relatively sparse tree canopy is always a great option as this mimics the azalea’s natural habitat and protects against sun burning the leaves whilst offering enough light to produce a great bloom.

Care for Azaleas in Winter

Azaleas in pots are far more susceptible to freezing temperatures than azaleas planted in gardens.

The foliage of the azalea can tolerate freezing temperatures and it is the roots that are at greater risk of frost damage. This is particularly true of azaleas as they are shallow-rooted and actually thrive when somewhat pot-bound.

There are a few options to protect potted azalea roots from freezing temperatures:

• As roots are the part of the plant that is at greatest risk, digging a hole in your garden soil for the pot and filling any gaps with soil or straw is a good way to keep the roots insulated from the cold.
• Alternatively, you can bring the pot indoors a place it by a window in your garage or in the house during the most severe weather.
• Place the pot in an even bigger pot. This is an effective strategy if you have a large unused pot in the garden and use a layer of straw, dead leaves, or other insulating material between the larger pot and the azalea pot to protect the roots against the cold.

I got a really interesting comment for a reader called Ed which I thought I’d share incase it helps anyone else out…

I just bought azalea in Ohio and getting a little late to plant. Can I keep it my garage which does not freeze but it does get cold in winter? – Ed

My advice to Ed is that keeping your azalea in a garage is a great idea even if it gets cold as what we are trying to avoid is freezing temperatures and as long as it stays above freezing you should be good.

Ideally the temperature should be between 0-10 degrees C (32 to 50 degrees F) as this replicates the azaleas period of cold dormancy in Winter which is crucial for flowering.

What I like to do is plant azaleas in a pot that is 16 inches in diameter in colder climates as larger pots have more soil capacity to help insulate the roots.

Do not water the azalea in Winter as the plant is dormant and additional water can increase the chance of fungal disease. Resume watering as soon as the weather warms up and you see new growth emerging.

Pruning Azaleas in Pots

From a maintenance standpoint, the great news is azaleas do not require regular pruning in the same way plants such as roses or lavenders do every year so it’s one less task in the garden.

Smaller species of azaleas such as the alpine azaleas most of the time do not need any pruning and often maintain a desirable mound shape that displays the flowers relatively evenly.

However, some occasional pruning of an azalea helps to maintain their appearance and shape, particularly if they have grown too large for their location.

You can prune at any time of year but the best time is after flowering. Whilst azaleas don’t require annual pruning they are tolerant to being cut back so you do not have to be overly cautious. Pruning azaleas (or rhododendrons) is the same whether they are in pots or in a garden border.

Here is a YouTube video for a visual guide on pruning azaleas:

Key Takeaways:

• Azaleas require potting soil that retains moisture and has an aerated, porous structure that allows excess water to drain away so the soil does not become boggy.
• Azaleas require watering as frequently as it takes to keep the soil moist. With well-prepared potting soil, azaleas may only require watering once per week during the growing season.
• Fertilizer is required in the Spring as pots have a limited capacity for nutrients. Use slow-release fertilizer once per year to ensure healthy growth and a good display of flowers.
• Azaleas prefer partial shade. The amount of light they will tolerate depends on how hot and dry your climate is. With potted azaleas, you can move the pot until you find the right balance of light (which promotes flowering) and shade (which protects leaves and reduces the risk of drought). 4 hours of morning sun followed by shade in the midday is a good balance for most azaleas.
• The best pot for azaleas is either ceramic, clay, or terracotta and around 16 inches across with drainage holes in the base.
• Potted azaleas have shallow roots that are vulnerable to the cold during Winter. In climates with harsh, freezing temperatures it may be necessary to bury the pot in the garden so the soil can insulate the roots or take the pot indoors in a garage for protection.
• Potted azaleas do not require annual pruning and some azaleas will not require any pruning at all. However, they can be pruned after flowering to help maintain a desirable, mound shape.