Why Are My Azaleas Not Blooming?

6 Reasons Why These Spectacular Shrubs Do Not Flower

Image: 'Golden Oriole' azalea.
'Golden Oriole' is so named because it is one of the yellow-flowering cultivars of azalea. David Beaulieu

"Why aren't my azaleas blooming?" One hears homeowners complaining about this frequently. We can all relate to their frustration, right, if not with this particular type of shrub, then with another? For example, some gardeners wait many years for the fascinating purple smoke bush (Cotinus coggygria) to bloom and fulfill its intriguing promise.

Reader, Donald writes, "I have two old azaleas that have slowed down in flower production this year.

I noticed that one azalea grew and leafed out just fine, but that it did not produce any flowers. I have treated my azaleas with Holly-tone fertilizer. I checked the soil pH, which was neutral, so I applied 8 ounces of sulfur. What else can I do to improve production of azalea flower buds?"

Reasons Why an Azalea Might Not Flower

"Why are my azalea bushes not blooming better?" Have you been asking yourself this question? You are not alone, as it is a concern that plagues many a gardener. It is a shame, too, because these bushes can be spectacular when in bloom. A type that many gardeners especially like is the Stewartstonian azalea. Be prepared to do a little research, because there are a number of potential problems to consider when trying to account for why azaleas fail to bloom; you will learn about them below.

Donald's train of thought certainly seems to be right on target: He made good decisions to deal with soil pH and to use the Holly-tone fertilizer.

The reason that he sought to lower the soil pH (that is, to make it more acidic) using sulfur is that azaleas are one of the acid-loving plants. Here are six other factors for someone with Donald's problem to check:

1. Location: Even if you have had the plants for a long time, it never hurts to double-check that they are properly located.

Nearby trees grow over time, increasing shade levels. Or, conversely, if you have lost any nearby trees or had a tree removed or limbed up, your azaleas will be getting more sun than they used to.

Some types of azaleas like a bit of shade, as well as some protection from winds. But when located in excessive shade, azaleas may produce a lot of greenery but fewer blooms.

2. Watering: There is a delicate balance to maintain here. Azaleas can't be allowed to dry out. But they do not like "wet feet" either. Mulching can help with water retention and protecting the roots from the heat (but your mulch layer should not be any deeper than 2-3 inches).

3. Fertilizer: While the Holly-tone is a good choice, stay away from fertilizers high in nitrogen, which will spur foliage growth but interfere with blooming.

4. Pruning: Did you change your pruning habits last year? For azaleas, the current year's blooms stem from flower buds developed during the prior summer. If you pruned later than normal last year, you may have inadvertently removed the flower buds.

5. Pest damage: This possible cause is related to the previous one. Except, here, it is the pest that does the "pruning," not the gardener. In some areas, the pest most likely to be the culprit is deer.

Since azaleas are not deer-resistant shrubs, it is entirely possible that Bambi came onto your property for a midnight snack one night and ate the flower buds right off your poor plant. What is the solution to this problem? If you live in deer country, you may want to erect deer fencing.

6. Weather: Try to remember what the weather has been like over the past year. That may be a lot to ask (some of us have trouble recalling yesterday's weather sometimes), but it could hold the key to your problem.

  • Was the weather hot and dry last summer? A period of drought during the prior year could have destroyed your azalea flower buds. This results in no flowers (or diminished flowering) for the current year. 
  • Was the weather especially cold this past winter? This is another condition responsible for killing azalea flower buds.
  • Conversely, lack of cold weather can sometimes result in a plant's not blooming, because some plants have a chilling requirement.
  • Were there any unseasonably warm periods in the fall or spring? Sometimes, azaleas are tricked into blooming during these periods (so-called "bud blast"). After such premature blooming, those azalea flower buds are lost to you for what would have been the upcoming blooming season.