If you’re not getting the glorious two-week display of blooms on your azalea, it may be due to disease or environmental factors. Here are the most common causes for your azalea not blooming and what to do about them.

Too much nitrogen in the soil encouraging foliage only

Your azalea may not be blooming because its environment has too much nitrogen. Maybe you’ve overdone this micro-nutrient in the fertiliser you fed your plant. Nitrogen is great for lush foliage growth but at the expense of the flowers.

What to do

Use a balanced fertiliser in which all the numbers are the same (e.g. 15-15-15). Better yet, use an acidifying fertiliser that introduces acid into the soil or dig plenty of ericaceous compost into the soil.

Not enough sun

Azaleas need sun to produce the best blooms. They do prefer dappled shade but too much shade prevents the plant from making the energy needed to create luscious blooms.

What to do

Rearrange your garden so that your azaleas have some direct sunlight in the morning. This may involve cutting down some surrounding plants, transplanting the azaleas to a better-suited location or transplanting them into pots. (See my How to grow and care for azaleas in pots article for details on how to do this.)

Potted rhododendron is root-bound

This problem is more often than not found in potted azaleas. But it can happen to azaleas in the ground if the plant was root-bound when you planted it. This occurs when all the roots are closely intertwined, forming a dense ball.

What to do

Carefully dig up the azalea and gently tease the roots apart. If the root ball is tightly wound up, you may need to use a knife and slice them apart. Look after the plant carefully after doing this as it may suffer from shock and stress.

Incorrect deadheading or pruning

Maybe you didn’t pay enough attention when removing the old blooms (deadheading) or cutting off the plant’s stems and branches (pruning). You may have cut off parts of the plant on which the early buds were forming. You wouldn’t necessarily notice at the time. But the next growing season, there wouldn’t be any new buds to develop into flowers.

What to do

Check that your azalea does have new buds from which flowers can develop. If not, there’s nothing you can do for this growing season. Be more careful when pruning next time, ensuring that you prune the branch above new growth. I don’t recommend pruning until it’s needed, but deadhead spent flowers just above a set of new shoots after they have finished flowering. Hard pruning and at the wrong time of year can remove the growth that produces the flower buds and result in no flowers in the following season

Petal blight

Petal blight is a fungus that travels through the air. If your plant has it, you do get new flowers but they collapse soon after they start to bloom. This disease lives through the winter on the old flowers.

What to do

If you don’t cut back your azalea at the start of winter, then do so at the start of spring. Remove all the old spent flowers. If it becomes a problem, to try and prevent it, you can use a fungicide when the flowers are just opening.

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