TALKING GARDENING with DOUG – Lichen

WHAT TO DO ABOUT LICHEN ON MY SHRUBS AND TREES

First, in doing some research for this blog, I found writing this blog more educational for me than I originally thought it would be. Over the years I have talked to many customers who wanted to know what was this grey looking barnacles growing on their dogwood trees or on their azalea plants. And, would it kill their plants?

Like with most anything in life, education and knowledge is the key to understanding lichen and their existence on our beloved trees and shrubs.

Here is a little biology lesson for you and for me:

Lichen is an unusual organism that is referred to as symbiotic between different organisms. Lichens are composed of a fungus (the body of the lichen) and algae (the part that photosynthesizes food for the fungus), living together in the same body. Lichens grow in a range of colors, from bright to grayish green. They are not parasitic or harmful to the plant. Lichen is not attributed to being the cause of poor health on any plant. Typically, less vigorous plants and plants with declining growth due to lack of light, poor conditions, and health are susceptible to lichen growth.

The number one question that I get from customers all the time. “My tree is dying!!! It has all of these greenish-gray growths on the trunks and branches. What is this disease and can I save my tree?” The bad news with my advice to these customers is that lichens are not the reason for the tree to be dying. When lichens are found growing on trees or shrubs, it may simply be a sign that a plant is naturally slow growing, such as a dogwood or Japanese maple, or that it is an older plant that is not growing at a vigorous rate. Lichens do not harm the plants they grow upon, but often plants that are struggling will be covered in them. When lichens are found growing prolifically on a plant that also has lots of dead twigs and branches it is usually a sign that something more serious is wrong. Lichen is rarely found on healthy, fast growing shrubs and trees because they are always shedding bark, making it difficult for lichen to attach. As I stated earlier, if you have a tree or shrub that now has lichen, and this has been accompanied by loss of leaves and dying stems, there is a very good chance your plant is not healthy.

WHAT TO DO ABOUT LICHEN?

Although there are no products listed to specifically kill lichen on shrubs and trees, spraying the lichen with COPPER FUNGICIDE can kill the fungal portion of lichen. Ultimately, the real question is why is the shrub or tree declining? We at The Great Big Greenhouse & Meadows Farms Nurseries are always here to help diagnose and discover what the cause could be. However, if the tree looks perfectly healthy and the lichen is on its trunk, there is generally no reason to be concerned. In my opinion, this lichen is just adding character to the bark of the host plant.

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9 thoughts on “TALKING GARDENING with DOUG – Lichen”

  1. I have 2 cherry trees that are next to each other and one of them has lichen on it. The leaves fell 3 to 4 weeks ago ! But I found out the roots of this tree is yellowish . What is cause if it ? Csn I prevent it from dying. Both of these trees are 17 years old . Last year on this particular one I saw this yellow guey stuff on it !! ? but this year no sign of it.

    • Ned,
      I have seen lichen growth on cherry trees. Not that uncommon because they are a slower growing tree that will not shed its bark. With this said, it seems that the one cherry tree is struggling to survive for one reason or another. You mention guey stuff on it. This guey stuff could be sap that is oozing out. Inspect the trunk of these cherry trees carefully and see if you see any holes in the trunk. If so, this could be caused by a boring insect that has gotten inside the trunk that is causing the tree(s) to decline. If it is borers then you may want to apply a systemic insect drench to both trees in order to kill any insects inside the trunk of the trees. One systemic drench that I recommend is by Bayer called 12 MONTH SYSTEMIC INSECT CONTROL. This is a soil drench product. The plant will take it up through its root system into the vascular system of the tree and give you insect protection for a year. Let me know if you have any further questions. Doug

  2. Hummingbirds use this material for their nest building in the spring. If it is available and good food supply, they will stay to raise a family, making your summer a pleasant hummer show. I leave any growths on my tress for nature. This aspect was not mentioned in your article.

    • Judy,
      First, thank for reading my blogs and thank you for taking time to give some feedback. I did not read anything about this aspect that you are sharing. So glad that you added this great information for our beloved hummingbirds. Again, thank you Judy. Take care, Doug

  3. I have a very big oak tree in my back yard it has lichen on it, doesn’t bother me any. Until it is falling off a lot of it is just all over the ground. I can find anywhere why this would happen. Tree looks healthy no dead branches. Any info? Thanks

  4. Hello! Thank you for your article and an opportunity to blog! It has been enlightening to read—including posters comments and your replies.

    I have a dogwood tree in my front yard flower garden. It’s been there at least 30 years, as my husband and I have been in our current home at least 24 years, and that tree was at least 25’ high when the house was purchased. There was no lichen on the tree then. It had a gorgeous triangular form, but has since had dead branches, which I have removed from time to time. The garden has been planted, replanted, and rearranged with many, many different plants over the years, including last year (I love gardening and a beautiful yard.). I’m adding more creeping Jenny this year. How may I accurately assess the issue with the dead branches, since the lichen isn’t the cause?

    I’m looking out a focal window now and seeing dead branches which need removing, allowing me to use my pole saw for the first time.😁

    • Good Afternoon, Ann
      This dogwood tree has some age to it. And, it seems to be in a declining state of health. Age may be the biggest factor for the causing of dying branches. A couple things – be sure that mulch is not build up high onto the trunk of this tree. Second, check the trunk for any small holes that could indicate a borer, which is an insect the borers into the wood and destroys the inside of the trunk. Other than this, I am not sure what to advise you as to what to do with your dogwood tree. Good luck, Doug

    • Phil,
      Good Morning. If you do spray off the lichen then I would think it would only be a temporary relief. They will return in time. Normally, lichens will attach to plants that are in a declining state. Doug

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