Trees are in the business of producing healthy branches with lots of green foliage. So when a branch dies it’s a cause for concern and as arborists, we want to know why. So here is an explanation on how to read the deadwood in your tree and better understand what your tree is telling you. 

Deadwood in an incense cedar

Isn’t dieback and deadwood the same thing?
All dieback is deadwood but not all deadwood is dieback. There is a difference between the two.

What is deadwood? 
Deadwood is any woody part of the tree that has died for any reason. Deadwood occurs frequently in crowded forests where trees are competing for sunlight. As the trees grow, they block the sun from reaching the lower branches, and over time, those branches die from a lack of sunlight. You can see in this picture, taken in a forest of Incense cedars, the lower half of the trunks are full of dead branches. Where there is more space between the trees, and more sunlight reaching the base, you will find more live branches on the lower half of the tree. On deciduous trees, where the canopy is more rounded, deadwood will occur in the interior of the tree for the same reason: lack of sunlight.

What is dieback? 
As was noted before, all dieback is deadwood but with a subtle difference. Dieback tends to form on the exterior portions of the tree where sunlight is accessible. As you can see in the photo of the citrus tree above, the dead branches are at the top of the trees, but there appears to be healthy foliage below the dieback. The tree is telling you that there is something wrong. 

What causes dieback in a tree?
Dieback is typically evidence of the early stage of drought stress due to a lack of water either from minimal application or the destruction of roots due to construction. Whatever the reason, a lack of water can weaken the tree and make it more susceptible to insect infestation and/or diseases. The green foliage located in the lower part of the canopy tells you that the tree is able to produce new foliage but doesn’t have enough water to push it up to the top of the tree. As the drought continues throughout 2021 and possibly into 2022, we will see more trees with dieback.

Dieback caused by disease in a Raywood ash

How do I tell if the dieback is being caused by a disease?
Generally, disease-related dieback is more sporadic whereas drought-related dieback is more uniform. The Raywood ash in this picture has dieback that looks very similar to the dieback caused by lack of light because it is located in the bottom part of the canopy. But an arborist who has been looking at Raywood ashes for the last 30 years will know instantly the tree is suffering from a vascular disease known as Botryosphaeria stevensii. It is a weak secondary pathogen, which is aggressive only when the ash trees are stressed, such as during a drought. It clogs the vascular system and prevents water and nutrients from moving through.

What should I do if I have dieback in my tree? 
The most important thing you can do is consult with a certified arborist. They have the experience and knowledge to confirm what is causing the dieback and make recommendations based on the tree’s overall health. 

Here is what an arborist might recommend:

  • The tree may have too much dieback and has entered the death spiral where no amount of pruning and/or watering will bring it back. It may be a waste of money to try and save it so the arborist may recommend its removal. However, if you are determined to do whatever it costs to save the tree, they may recommend a “Two-Part Removal” where you remove the dieback now with the understanding that the tree may die and have to be removed at a later date.  
  • The arborist may recommend the removal of dieback for safety reasons (if left long enough deadwood will eventually break off and fall to the ground) and to set a baseline to see if the tree is recovering or continuing to decline.
  • If you have cut back on your watering because of the drought, you might consider watering your tree. You can refer to the June 2021 newsletter entitled “How to Water Your Tree in a Drought” for directions on how to do that. We have a copy on our website:

What does it mean when the arborist recommends to “remove dieback only”?  
Usually, it means the tree is on the knife-edge between further decline and death or recovering and continuing to live. The arborist knows that every green leaf is critical to the tree’s recovery. Those green leaves are going to produce the food to feed the tree and bring it back from the brink. Depending on how extensive the dieback is there is a possibility that its removal will leave the tree misshapen and you might be tempted to ask the arborist to shape the tree by removing green foliage for balance. But if you really want to save the tree you may have to live with a lopsided tree until it recovers. 

Hopefully, this article has given you insight into the health of your tree and information on how to interpret deadwood. As always, if you have any questions about your tree do not hesitate to call our office and set up an appointment to meet with one of our arborists!