The most common reasons for azaleas not growing are:
- Azaleas need rich soils. Nutrient poor soils (such as sandy soils) may not have enough nutrients for azaleas to grow fully.
- The use of mulch that is not fully decomposed can cause a temporary nitrogen deficit in the soil which limits the azaleas roots access to nitrogen and slows growth.
- Drought in the growing season can stunt growth. Azaleas require the soil to be moist consistently.
- Azaleas require acidic soil of pH 4-6. Azaleas cannot access nutrients in pH neutral or alkaline soils which stops growth and can kill the plant.
- Some varieties only grow to around 16 inches in height. If the leaves are a healthy dark green, it is likely you have a dwarf variety of azalea.
Keep reading for more information to diagnose why your azalea is not growing and for how to solve the problem…
1. Nutrient Poor Soils
The most common reason for azaleas not growing is because of a lack of nutrients in the soil.
Azaleas however are not particularly heavy feeders and may not require any additional fertilizing if the soil has been prepared correctly. (Read my guide for preparing garden soil for planting azaleas).
The two main reasons for low nutrient soils are:
- Sandy soils (Inorganic materials such as sand and stone don’t contribute much nutrients to the soil and they do not retain nutrients effectively).
- The use of mulch or soil amendments which is not fully decomposed can cause a temporary nitrogen deficit in the soil.
For good growth, Azaleas require rich soils with a high organic content as this provides their optimal soil structure, balance of moisture and enough nutrients for them to flower and thrive.
Sandy soils tend to drain too quickly and they do not retain water soluble nutrients (such as nitrogen and potassium) as effectively as soils with a proportion of clay content (loam soils are the best for growing azaleas).
If you azalea is planted in sandy soils then you will need to either dig up the azalea and amend the soil with plenty of organic matter or transplant the azalea to pots or raised beds where you can easily customise the soil conditions to suit the requirements of azalea. (Read my guide for the optimal potting mix for azaleas).
If the azalea looks relatively healthy then I would recommend that you amend the soil in the Fall as this is the best time to move azaleas as the soils is still warm from Summer and there is still some moisture in the soil.
The Azalea should recover and start to grow again in the next growing season.
2. Mulch Causing a Nitrogen Deficit, Slows Growth
The use of mulch and organic materials when planted and caring for azaleas is very important as they add nutrients to the soil and help to keep the soil at the correct balance of moisture in the Summer.
However it is important to use organic material that is fully decomposed.
Materials such as compost, leaf mould, manure and wood bark are often used as both soil amendments before planting azaleas and as mulch to help conserve moisture after they are planted.
If these organic materials are relatively immature and not fully decomposed before you use them around you azalea then they can cause a temporary nitrogen deficit in the soil.
Nitrogen (N) along with Phosphors (P) and Potassium (K) are the nutrients that are required in the greatest quantities by azaleas, with Nitrogen in particular being important for stimulating new growth. This is why a deficit of nitrogen in the soil can cause your azalea to not grow.
A nitrogen deficit is more common when using wood bark or wood chip as a mulch. When organic material is fully decomposed it will add nitrogen to the soil. However the process of decomposition actually requires significant amounts of nitrogen to rot down.
This extra nitrogen required for decomposing organic matter is drawn up from the soil during the process. Whilst the decomposition is happening around the roots of the azalea, there will be less nitrogen available for uptake which can stunt the growth of the plant.
The foliage turning yellow is another indication of a lack of Nitrogen in the soil. (Read my guide if your azalea has with yellow leaves).
Foruntunaley azaleas are long lived plants and a temporary lack of nitrogen in the soil will stunt the growth of the plant for that particular year but there is no reason why it will not recover with some adjustments.
To fix a Nitrogen deficit in the soil or to deal with soils that may be lacking in the nutrients that azaleas require, then the best course of action is to use a specialised fertilizer.
Whilst it is possible to use general plant fertilizers to treat an azalea that are not growing, I have seen much better results with a specific azalea fertilizer such as Miracle grow slow release plant food. This fertilizer contains all the nutrients that the plant will need at the right concentrations that the azalea requires.
A specialised fertilizer can also contribute to the acidity of the soil (Azaleas prefer acidic soils with a pH of between 4-6) which will help the roots access nutrients.
The granular formulation is best as this slowly releases the nutrients at the right time as the soil heats up at the start of the growing season.
Apply the fertilizer at the start of Spring as they azalea emerges from its Winter dormancy and the azalea should start to growing well.
The added nitrogen from the fertilizer should promote new growth in the azalea and it should produce blooms later in the season.
Do not be tempted to add fertilizer at anytime of year as this can stimulate new growth when the plant should be preparing for Winter, so always wait for the Spring.
Additionally I should reemphasize that you should always use well rotted material around your azaleas.
Leave organic material in a compost heap for a year by which time it will be beneficial to use as a mulch to conserve moisture during the Summer.
If you want to distribute wood chip or bark around you azaleas as a mulch then it is best to lay some planting weed control barrier between the soil and the wood bark and you should not have any problems.
3. Drought Stunts Azalea Growth
Azaleas require consistent moisture around the roots at all times. The soil should be moist without being saturated as boggy soil will promote the conditions that cause root rot (Phytophthora).
If the azalea experiences drought and the surrounding soil dries out then this will stress you azalea which will cause it not to grow.
Azaleas can recover from drought if properly watered and with some adjustments but it can slow down growth and prevent flowering.
Azaleas are shallow rooted plants so they are often one of the first plants in your garden that will show signs of stress if the soil becomes dry.
As an immediate response the plant may wilt and the leaves may curl and turn somewhat brown/yellow. In which case you should water the plant immediately.
However even if you have addressed the cause of the drought the growth may be stunted all through the growing season.
The solution to drought is to:
- Increase the frequency of watering of the azalea.
- Apply a layer of well rotted organic matter as mulch around the base of the plant.
It is impossible to specifically tell you how much to water you azalea as there are many factors involved such as…
- is the climate arid or humid?
- Has the soil been prepare properly or does it drain quickly? etc.
So the best advice is that you need to water the azalea as frequently as it takes to keep the soil consistently moist (but not saturated). In most cases 4 litres or a gallon of water once or twice per week will meet the azaleas watering requirements. (Watering requirements will depend on several factors. Read my guide on watering azaleas for how much and how often to water azaleas according to the conditions).
Test the soil regularly with your finger to see is you can detect moisture. If the soil is drying out then give the azalea a good soak. Soon enough you will get a good sense of how much water you azalea needs in your specific garden.
Additionally it is important to apply a mulch at the start of Spring. Mulch has many benefits for azaleas but most importantly:
- Mulch helps to reduce soil evaporation which keeps the soil moist
- Mulch will improve the soil texture at the surface which makes it easier for rain and water to infiltrate the soil and reach the roots
- Organic matter has the capacity to absorb moisture but allow for excess water to drain away so the soil does not become boggy
This will help to keep the soil moist so that the roots of the azalea can draw upon water when they need to without being in soil that is saturated which causes root rot.
Apply a one inch layer of material (ideally leaf mould, compost or well rotted manure) around the root ball of the azalea on the surface of the soil. Leave a gap of a few inches between the mulch and the wood of the azalea to keep the plant healthy.
With regular mulching, the soil profile will improve over time so that it absorbs more water which will cut down on how much water the azalea requires and the plant will be far less vulnerable during the hottest days of the year.
With an application of mulch in the spring and watering you azalea the required amount to keep the soil moist, the azalea should recover and stay healthy, however you may have to wait to the next growing season before the plant starts growing as normal.
4. Soil pH and Azalea Growth
Azaleas require acidic soil of pH 4-6 to be able to grow properly. If the soil is too close to pH neutral (7) or the soil as alkaline then the azalea will not grow to the same extent and may even die.
Azaleas require acidic soil to access certain nutrients such as iron so if the pH is too high they cannot photosynthesise effectively and will not live long.
If other acidic soil loving plants such rhododendrons, camellias and roses are all growing happily in your garden then you should have the right soil pH for growing azaleas so it may be drought or a lack of soil nutrients that may cause the lack of growth.
Soils can be alkaline for several reasons, such as the local geology or even building work can cause localised pockets of alkalinity in a garden.
If you are unsure of your soils pH then I would recommend that you test it with a soil gauge which are easy to use and available for a great price on Amazon.
If you can ascertain the soils pH then you can save yourself time and money in the long term as you know which plants are suitable for your garden soil and you can address any issues that may be caused by other factors (such as building work) affecting the pH.
Garden soil that is naturally alkaline is difficult to amend over a long term and requires ongoing maintenance at great effort and cost. It is a much better idea to transplant the azalea into a pot or raised bed where you can control the soil so that it is suitable for azaleas and other plants that prefer acidic soil.
I also recommend watering azaleas and other plants in acidic soil with rain water as rain water is slightly acidic whereas tap water can be pH neutral or even alkaline in some areas.
The use of a specialised ericaceous fertilizer for acidic soils will also help to maintain the optimal soil pH for growing azaleas (ericaceous in this context just means for acidic conditions).
If you find the soil is significantly outside of the 4-6 pH acidic range then transplant the azalea to a pot with the right conditions as quickly as possible.
If the soil is only slightly outside of the range at say, pH 7 then you can temporarily dig out the azalea and amend the soil with peat moss or a bag of ericaceous soil which are both available online or in any good garden center. Peat moss is naturally acidic with a pH of around 5 so it will help to contribute to a more acidic soil pH to keep the azalea happy.
Recovery of an azalea in the wrong soil will depend on how far out of the range the pH of the soil was but the plant should begin to recover and growth should resume to normal in the next season.
5. Slow Growing or Smaller Varieties
Azaleas grow naturally across the continent of North America, Europe and Asia. Therefore they have been wildly cultivated in to a number of different varieties of different sizes by many gardeners and botanists.
Some varieties such as ‘aboreum’ grow relatively large to over 6 foot whereas other varieties such as ‘calostrotum’ are naturally slower growing and will only grow to 16 inches proportionally.
Therefore you azalea may just be a dwarf variety that should only grow to a modest height.
If the leaves are a deep green in colour then it is likely the azalea is in good health and may not grow any more then it already has, although they can live for over 100 years.
- The most common reason for azaleas not growing is due to a lack of nutrients in the soil. This can be caused by a decomposing organic matter causing a temporary nitrogen deficit in the soil. The solution is to add a specialised fertilizer for azaleas to restore the levels of nitrogen in the soil and other nutrients so that they azalea can grow.
- Poor soil that is sandy or stony will not be high in nutrients. The solution is to amend the soil with organic matter to improve the available nutrients in the soil so that the azalea can grow healthily.
- Drought is another cause of azaleas not growing. Azaleas are vulnerable to drought because of their shallow root system. Water the azaleas as frequently as is required to keep the soil moist and use a mulch to help conserve moisture.
- Soil pH is another factor that can prevent azaleas from growing. Azaleas require acidic soil that is pH 4-6. If the soil is closer to neutral or even alkaline then azalea roots cannot access the nutrients they require and the plant will not grow and may die. Transplant the azalea to a pot or amend the soil with peat moss or ericaceous soil (both acidic) to bring the soil pH into the optimal range for azaleas and they should resume growing the following Spring.
- Some varieties of azalea grow more then others. Dwarf varieties may only grow to 16 inches in height whereas larger varieties can grow more then 6 ft.