Azalea flowers turn brown and don't open - Ask Extension
Hello and thank you in advance for your help!
I have three older azalea bushes in my front yard. In past years they bloomed as expected and did not s...
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Azalea flowers turn brown and don't open #667368
Asked July 22, 2020, 1:00 PM EDT
Hello and thank you in advance for your help!
I have three older azalea bushes in my front yard. In past years they bloomed as expected and did not show any signs of declining health. However, this year I have noticed that branches have gray/green scale (lichens?) and flowers bud but immediately turn brown and do not open. Eventually the branches seem to die. The cut dead branches do not show signs of any boring insects. In addition, leaves tend to stay green until the branch dies out (not curling or browning). I can'r figure out how to save this plant (if possible). The bush has really declined over the past few months. I have started to add acidic plant food to the soil. Not sure if it helps.
Montgomery County Maryland
Expert Response
Old azaleas can become scraggly and leggy and benefit from rejuvenation. Renewal pruning (technique #4 on this page - https://extension.umd.edu/hgic/topics/pruning-shrubs-and-hedges) will remove old branches entirely which allows more light into the shrub's interior and will encourage new growth. This is a gradual process which takes three or so years to avoid removing too much of the plant's growth at once. Pruning is best done in spring, just after flowering, as this is when new stem and leaf growth naturally begins to emerge. It could be done just prior to flowering instead if you do not mind missing-out on some of the bloom for that year.
This plant appears to have flowered, though we cannot clearly see the spent flowers closely enough to tell for sure. It doesn't look as if the buds withered without first opening, but since we had multiple late-season cold snaps this spring, they could have been frost-killed overnight just as they were reaching full bloom.
The lichen growth is harmless to the plant but indicates that more light is now reaching the bark - a sign the leaves are growing too small and sparsely. The vigorous new growth that will replace these old branches should be denser with larger leaves. Using a mild dose of fertilizer (ideally a slow-release one for acid-loving plants) should help the plant rebound after each spring's trim. Since you have recently fertilized it, no more fertilizing is needed for this year.
Branch dieback could the be the result of decline from loss of vigor over time or the result of root loss due to moisture issues. Azaleas prefer even soil moisture - not wet and poorly-drained nor drought-prone - so the unusual weather patterns of excessively-wet springs and late-season drought the past few years could have resulted in some root death which the plants are still recovering from. If their root system is competing with that of trees and in a raised bed (which tend to stay drier overall), periodic supplemental watering should help in dry summer and autumn weather. Both infections and wood-boring insects that cause branch dieback tend to show symptoms of leaf wilting or browning prior to complete branch death, which does not sound like the case here.
Miri
This plant appears to have flowered, though we cannot clearly see the spent flowers closely enough to tell for sure. It doesn't look as if the buds withered without first opening, but since we had multiple late-season cold snaps this spring, they could have been frost-killed overnight just as they were reaching full bloom.
The lichen growth is harmless to the plant but indicates that more light is now reaching the bark - a sign the leaves are growing too small and sparsely. The vigorous new growth that will replace these old branches should be denser with larger leaves. Using a mild dose of fertilizer (ideally a slow-release one for acid-loving plants) should help the plant rebound after each spring's trim. Since you have recently fertilized it, no more fertilizing is needed for this year.
Branch dieback could the be the result of decline from loss of vigor over time or the result of root loss due to moisture issues. Azaleas prefer even soil moisture - not wet and poorly-drained nor drought-prone - so the unusual weather patterns of excessively-wet springs and late-season drought the past few years could have resulted in some root death which the plants are still recovering from. If their root system is competing with that of trees and in a raised bed (which tend to stay drier overall), periodic supplemental watering should help in dry summer and autumn weather. Both infections and wood-boring insects that cause branch dieback tend to show symptoms of leaf wilting or browning prior to complete branch death, which does not sound like the case here.
Miri
