The Q&A Archives: Dahlia problem

Question: I am new to growing dahlias. I have some yellow ones and in the course of 4 days, perfectly good blossoms turned completely brown. They are not falling off the stem at all, and in that respect seem healthy,but they have definitely changed color. Two of the flowers are newly opened ones.

We were away during that period and cannot speak of the weather here in Northern VA then. Can you tell me what the problem could be?

Answer: Based on your description, I suspect it may be botrytis which is a fungal infection. If so, the dry looking blooms are likely to develop a fuzzy gray mold on them. Remove the affected flowers and dispose of them in the trash, then make sure not to wet the foliage or blooms when you water the plants. Make sure your plants are spaced far enough apart for good air circulation. Do not work on the plants when they are wet from dew or rain.

If you water (and there has been quite a long dry spell in your area) you need to water slowly and deeply so it soaks down to where the roots are. Dahlias need an evenly moist soil, it should be wet like a sponge but not saturated/sopping wet. When in bloom, they need about two inches of water a week as a rule of thumb which is more than they needed, maybe double what they needed before they started to bloom.

You might also check with your county extension to see if they are aware of any particular problems with dahlias in your area in recent weeks. I hope this helps.

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