Prune Now Before It’s Too Late
With all the rain we have received this year, azaleas and chrysanthemums have produced an abundance of new growth. If you want those plants to produce an abundance of flowers — this fall for chrysanthemums and next year for azaleas — get out your shears this week.
Chrysanthemums are short-day plants, which means that they will start initiating flower buds around mid-August. Prune any later than this week, and they will produce fewer flowers, which will be smaller in size and on shorter stems. Later pruning won’t give the plants adequate time to generate new branches for flower buds to develop. For chrysanthemums, flower buds are not only developed at the ends of each stem, but also in the axil of the uppermost leaves.
Azaleas generally stop producing new vegetative growth in mid- to late- August. As soon as the tops of the plants stop growing, they begin generating flower buds at the ends of every branch. If you wait to sheer azaleas in August, the plants will not have adequate time to produce new branches upon which flower buds can be produced. Since woody plants such as azaleas are slow to recover from being sheered, there needs to be sufficient time for them to produce two to three inches of new growth before initiating buds.
When you prune, do it right. When cutting azaleas, always allow at least one, preferably two, inches of new growth to remain on the plant. If you sheer the top of the plant back to its original height, the new growth will have to originate from last year’s growth, which will result in fewer new branches for flower bud initiation. With one to two inches of new growth remaining on the plants, new branches will emerge from the axils of the existing leaves, resulting in more dense foliage with many branches upon which flower buds can grow and flower next spring.
Footnote for Azaleas
If your azaleas lost most of their lower leaves last winter, you may wish to apply ammonium sulfate fertilizer after the first killing frost this fall. The loss of lower leaves is a clear indication that the plants are not absorbing sufficient ammonium nitrogen. Pruning will result in a greater need for ammonium nitrogen because there will be many more branches and flower buds to feed. By fertilizing with ammonium sulfate after the first killing frost, you will have not only healthier looking plants in the spring but also a greater abundance of flowers.
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