Whole parts of plant dying off at once - Ask Extension
As if overnight, parts of these three plants are dying off. I have watered them all and did do some cutting out of dead wood. They were planted as par...
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Whole parts of plant dying off at once #876952
Asked July 12, 2024, 10:59 AM EDT
As if overnight, parts of these three plants are dying off. I have watered them all and did do some cutting out of dead wood. They were planted as part of a garden in Spring 2023. Is there anything I can do to save these plants? Will my other plants be attacked as well? Help!
Anne Arundel County Maryland
Expert Response
Do you know what species the plants are? Plant ID plays an important role in making a diagnosis. Some of the growth pictured looks like Summersweet (Clethra), but the rest is too wilted for us to ID.
Did any wilting occur before watering began? Both this year (so far) and most of last year's growing season have been plagued by drought for much of the state, which is stressing even well-established plants. Being so new and still in their establishment period, have these plants been monitored for watering needs regularly this season as well as last year? (Feeling the soil around five inches deep and watering only once it started to get somewhat dry to the touch at that depth.) Wilting and branch dieback can occur with both over- and under-watering, and the symptoms overlap so much that alone they usually cannot confirm which issue occurred. While it may seem unlikely to over-water species that normally live in damp habitats (as Clethra can in the wild), it can occur in certain conditions.
Even though the symptoms manifested suddenly, the issue was probably building up to that point beforehand. One culprit we cannot rule-out is Southern Blight, a fungal disease common to various perennial plants but which can occur on shrubs as well. Botryosphaeria canker, a different fungal infection, can also occur on plants that were previously stressed by high heat, drought, or other environmental conditions. (The linked page focuses on Rhododendron, but this fungus can affect a wide variety of shrub species, especially those that prefer to remain moist.) Neither is treatable if they are responsible for dieback, and prevention centers around minimizing plant stress before it predisposes them to fungal attack. Isolated branches dying on an otherwise healthy-looking shrub can be pruned off, as you have done.
When the shrubs were installed, were the root balls well-loosened/disentangled from any root-bound state they may have been in? If not, that can make watering and monitoring for moisture difficult to do well, since it hampers establishment and can interfere with moisture absorption and drainage. (The soil within and outside of the root ball dry out and retain water to different degrees.)
For now, all you can do is to make sure the soil around the roots is moist to at least a six-inch depth, and keep any mulch a few inches away from the crown (where stems emerge from the ground) so the crown gets good air circulation. This applies to the shrub whose leaves are still mostly green; the shrub pictured that is in worse shape likely needs to be replaced because we do not expect it to recover.
Miri
Did any wilting occur before watering began? Both this year (so far) and most of last year's growing season have been plagued by drought for much of the state, which is stressing even well-established plants. Being so new and still in their establishment period, have these plants been monitored for watering needs regularly this season as well as last year? (Feeling the soil around five inches deep and watering only once it started to get somewhat dry to the touch at that depth.) Wilting and branch dieback can occur with both over- and under-watering, and the symptoms overlap so much that alone they usually cannot confirm which issue occurred. While it may seem unlikely to over-water species that normally live in damp habitats (as Clethra can in the wild), it can occur in certain conditions.
Even though the symptoms manifested suddenly, the issue was probably building up to that point beforehand. One culprit we cannot rule-out is Southern Blight, a fungal disease common to various perennial plants but which can occur on shrubs as well. Botryosphaeria canker, a different fungal infection, can also occur on plants that were previously stressed by high heat, drought, or other environmental conditions. (The linked page focuses on Rhododendron, but this fungus can affect a wide variety of shrub species, especially those that prefer to remain moist.) Neither is treatable if they are responsible for dieback, and prevention centers around minimizing plant stress before it predisposes them to fungal attack. Isolated branches dying on an otherwise healthy-looking shrub can be pruned off, as you have done.
When the shrubs were installed, were the root balls well-loosened/disentangled from any root-bound state they may have been in? If not, that can make watering and monitoring for moisture difficult to do well, since it hampers establishment and can interfere with moisture absorption and drainage. (The soil within and outside of the root ball dry out and retain water to different degrees.)
For now, all you can do is to make sure the soil around the roots is moist to at least a six-inch depth, and keep any mulch a few inches away from the crown (where stems emerge from the ground) so the crown gets good air circulation. This applies to the shrub whose leaves are still mostly green; the shrub pictured that is in worse shape likely needs to be replaced because we do not expect it to recover.
Miri
