Ask The Arborist

The City Arborist is an expert in arboriculture and urban forestry who is responsible for overseeing the health of trees on City property, managing the urban forest, and reviewing and making decisions on tree removal applications on private property. When we have questions about anything from the proper trees to plant in a given location to how to address trees that are underperforming or showing signs of disease, the City Arborist has the answers.


Now, we want to give Alpharetta residents the opportunity to ask the City Arborist questions about tree selection and care, insect and disease issues, tree conservation, and tree management. Send us your tree-related questions, and our arborist will select one each month to answer. The answers will be posted on this page and featured on our social media channels and e-newsletter.

Recent Questions & Answers:

Question: What is happening to this pine tree?


Tree-Image-For-QuestionA. This is a good question because this is a prominent issue, I see on pine trees around Alpharetta. What you see in this photograph is a pine exhibiting one stage in the Life Cycle of the Fusiform Rust Fungus. This fungus has various stages it goes through on a pine tree, starting on a young pine and developing over a few years. A part of this cycle includes a stage on a nearby oak leaf, growing spores that will eventually find their way to another pine, starting the cycle all over. This canker will not spread from pine to pine or spread to another area on the same pine. Each infection is a separate infection and must include a stage on the leaf of a nearby oak. 

Young pine seedlings and saplings within the landscape can be treated with a fungicide, up until about 5 years old. However, once the pine is infected you can prune out infected limbs as a treatment, but once it shows up on the main trunk there is no known treatment. 

This fungus ultimately can become a canker on the trunk of a mature pine. This canker is typically oblong in shape, is sunken, and has the appearance of a target. If this canker encompasses a large portion of the trunk, typically more than 30% it can be a weak spot. If any of your pines exhibit a canker this large, it is recommended to have an ISA Certified Arborist assess the tree.

Here are some links for additional information.

 Q. I often prune my own trees, but with large branches, I am curious about the correct pruning cut to prevent tearing. I have heard that arborists cut a notch above and one below. What is the correct order, spacing, and depth of each cut?


A. Let’s start with a word on safety because pruning large trees can be dangerous. If you are not able to safely get your head and shoulders above the branch or if the pruning requires power equipment, you should hire a qualified tree care company to avoid the risk of injury. Certified arborists can determine the type of pruning necessary to improve the health, appearance, and safety of your trees and also provide a trained crew with the proper equipment and insurance.


The notches you mentioned are part of a technique arborists use to reduce the possibility of tearing the bark on the trunk of the tree. The first cut is just an undercut notch and should be made about 12 to 18 inches from the limb’s point of attachment. The second cut is made from the top, a few inches out from the first undercut. This second cut should be made all the way through until the limb falls. This removes the weight of the limb, leaving a 12- to 18-inch stub. Now the stub can be removed with no risk of tearing the bark on the trunk since the weight of the branch is gone. The third and final cut is made just outside the branch collar (raised tissue that separates the branch from the trunk). It is very important not to cut into the branch collar, as this area contains the special cells that allow the tree to compartmentalize the wound.


Q. Why do people mulch around trees and in planting beds?


A. There are several advantages to mulching. Beyond the obvious aesthetic benefit, organic mulches help to simulate forest floor conditions for trees, control weeds, and retain soil moisture. Trees evolved with a deep litter layer of leaves and decaying wood around them, so planting a tree in a lawn area surrounded by turf is bound to cause problems. A ring of mulch around a tree eliminates the competition for water and nutrients between the tree and the turf, which will promote the health of both. Organic mulches also help build soil fertility and structure.

You can have too much of a good thing, though, so keep in mind that two to three inches of mulch depth is the maximum you should use, and mulch should not touch the trunk of the tree. Leave a mulch free zone 4-6” around the trunk of the tree. Deep piles of mulch restrict oxygen to roots and water penetration to the critical root zone. It can also provide many stem and root rot organisms with an ideal environment to establish and multiply.