Growth on dying azalea - Ask Extension
My azalea plants have a greenish/white lichens like growth on the bark. The stems are turning black and dying and the leaves are also turning black I...
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Growth on dying azalea #215036
Asked September 30, 2014, 10:17 PM EDT
My azalea plants have a greenish/white lichens like growth on the bark. The stems are turning black and dying and the leaves are also turning black I have a 20 year old locus tree that also is covered in this same greenish/ white substance for the first time ever and also appears to be dying. What is it and how to I treat? Thank you in advance for your response.
Centre County Pennsylvania
Expert Response
Dear Homeowner,
Lichens on branches will not harm the plant, but is an indicator that the plant is not growing vigorously.
Here is an explanation of why lichens start to grow on shrub/tree branches: \( from the website; http://www.caes.uga.edu/extension/jefferson/documents/Crawford11092011.pdf
"It’s a good analogy to describe why lichens or moss often don’t grow on young, healthy, actively
growing trees. As long as an object is moving, moss or lichens can’t take hold. This is the case when the plant ceases to grow and isn’t making new bark each year. It goes into decline and as its leaf canopy thins and allows sunlight to enter, lichens take advantage and develop
where these conditions support their growth. The homeowner needs to look for environmental stresses that may be preventing vigorous plant
growth. In the case of trees planted in small islands in the middle of parking lots, stress is caused by limited soil and root growth, compacted soils and heat stress due to paved surfaces.
Other stresses include improper planting resulting in compacted root ball, inadequate soil pH, low fertility, poor drainage, over-watering, plant competition, drought , improper pruning or the presence of insects/disease.
Lichens aren’t killing plants but they’re a sign that something else is! If you remove what’s stressing your trees or shrubs, the lichens or moss will go away."
Last winter's severe temperatures, and this summer's excess rain may have weakened your plants, especially if they are sited in a poor drainage area.
This time of year is not optimal for doing anything to help improve the plant's health. The older deciduous azalea may benefit from a rejuvenation pruning, to spark some new growth. Next spring, after the azalea blooms, prune out about 1/3 of the stems. Here is a link to help you figure out how to do this , from Purdue Extension:
http://www.hort.purdue.edu/ext/ho-4.pdf See Figure 13 .
Wait and see how the plants look next spring. If they have some healthy new growth, you can have a soil test done and see if they need some nutrients. If they again look poorly, you may have to consider removing them.
As always, please contact you Centre County Extension Office, by phone or email,
with further questions.
Lichens on branches will not harm the plant, but is an indicator that the plant is not growing vigorously.
Here is an explanation of why lichens start to grow on shrub/tree branches: \( from the website; http://www.caes.uga.edu/extension/jefferson/documents/Crawford11092011.pdf
"It’s a good analogy to describe why lichens or moss often don’t grow on young, healthy, actively
growing trees. As long as an object is moving, moss or lichens can’t take hold. This is the case when the plant ceases to grow and isn’t making new bark each year. It goes into decline and as its leaf canopy thins and allows sunlight to enter, lichens take advantage and develop
where these conditions support their growth. The homeowner needs to look for environmental stresses that may be preventing vigorous plant
growth. In the case of trees planted in small islands in the middle of parking lots, stress is caused by limited soil and root growth, compacted soils and heat stress due to paved surfaces.
Other stresses include improper planting resulting in compacted root ball, inadequate soil pH, low fertility, poor drainage, over-watering, plant competition, drought , improper pruning or the presence of insects/disease.
Lichens aren’t killing plants but they’re a sign that something else is! If you remove what’s stressing your trees or shrubs, the lichens or moss will go away."
Last winter's severe temperatures, and this summer's excess rain may have weakened your plants, especially if they are sited in a poor drainage area.
This time of year is not optimal for doing anything to help improve the plant's health. The older deciduous azalea may benefit from a rejuvenation pruning, to spark some new growth. Next spring, after the azalea blooms, prune out about 1/3 of the stems. Here is a link to help you figure out how to do this , from Purdue Extension:
http://www.hort.purdue.edu/ext/ho-4.pdf See Figure 13 .
Wait and see how the plants look next spring. If they have some healthy new growth, you can have a soil test done and see if they need some nutrients. If they again look poorly, you may have to consider removing them.
As always, please contact you Centre County Extension Office, by phone or email,
with further questions.
