Black covering on flowers - Ask Extension
Hello. There is a cluster of bushes and plants that are covered in a black film. These plants were all just planted in may of this year. How can I tre...
Knowledgebase
Black covering on flowers #846866
Asked August 22, 2023, 6:06 PM EDT
Hello. There is a cluster of bushes and plants that are covered in a black film. These plants were all just planted in may of this year. How can I treat this? Is it a fungus?
Montgomery County Maryland
Expert Response
These are leaf spot infections (some are caused by fungi, some by bacteria) and while we cannot determine which exact pathogens are responsible for the spotting on either plant, we can say that they rarely cause long-term plant damage. The worst one or two of the spotted leaves on the Hellebore can be clipped off and thrown away, but you don't need to remove them all. (Though most gardeners trim off the old, weather-damaged Hellebore foliage at the end of winter, just before blooms and fresh foliage appear, to give them a tidier appearance.)
When the Magnolia sheds its leaves later this autumn, you could rake them up and dispose of them to minimize how many infectious spores remain at the base of the tree, though this is not a foolproof way to completely prevent infection in a future year. Plant diseases can be affected by weather, where one year an outbreak might be severe but nearly absent in another year if the weather patterns were different when spores were creating infections. If you irrigate plants during periods of drought or dry weather, try to avoid wetting leaves in the process (such as when sprinklers are used), since wet leaf surfaces can be more vulnerable to infection. If this is unavoidable when watering, then just try to water early enough in the day so that foliage can dry by nightfall.
Fungicide will not cure existing infection and is rarely practical to try using on most perennials or trees/shrubs as a preventative. If you monitor the plants for watering needs during dry spells, though, this will help keep the roots healthy so the plants are better able to tolerate any damage and recover well the following spring when new leaves emerge.
Miri
When the Magnolia sheds its leaves later this autumn, you could rake them up and dispose of them to minimize how many infectious spores remain at the base of the tree, though this is not a foolproof way to completely prevent infection in a future year. Plant diseases can be affected by weather, where one year an outbreak might be severe but nearly absent in another year if the weather patterns were different when spores were creating infections. If you irrigate plants during periods of drought or dry weather, try to avoid wetting leaves in the process (such as when sprinklers are used), since wet leaf surfaces can be more vulnerable to infection. If this is unavoidable when watering, then just try to water early enough in the day so that foliage can dry by nightfall.
Fungicide will not cure existing infection and is rarely practical to try using on most perennials or trees/shrubs as a preventative. If you monitor the plants for watering needs during dry spells, though, this will help keep the roots healthy so the plants are better able to tolerate any damage and recover well the following spring when new leaves emerge.
Miri
