In this episode of Ask Danny, arborist Billy Allen offers his expert advice on planting and pruning.
Billy is an ISA Certified Arborist, AUFA Certified Urban Forester, ALNLA Certified Landscape Professional and more.
He is the owner and operator of Top Notch Tree Care, where he provides services such as residential and commercial pruning and/or removal, as well as pre-construction tree conservation consulting, disease diagnosis and treatment, and health and structural assessments. It also provides plant health services such as tree fertilization, pesticide application and soil compaction mitigation.
When to plant
What is the best time of year to plant?
Billy: For the best time to plant a tree, the vast majority of the time it will be while the tree is entering dormancy – late fall, early winter. When you plant a tree, you will lose a lot of roots, so you want to keep the heat stress on the plant as low as possible.
An exception would be citrus trees. You want to plant them after the last spring frost because a good freeze can be detrimental to them.
The biggest problem I see people have when planting has to do with depth. Deeper is not better. Think of it this way: Who plants a tree in the forest? The answer is no one. The seed falls to the ground, organic material covers it and it germinates.
You want the topmost root of that plant, whether it’s a tree or a shrub, to be level or slightly above. If you have a lot of clay in your soil, add something to the soil to soften that very fine material. You want to till three to four times the size of the root ball and prepare that soil to make it more beneficial for the roots to grow.
When pruning
When is the best time to prune a tree?
Billy: You can prune at any time of the year as long as you do it right. I see a lot of wrong pruning, especially on crape myrtles, azaleas and live oaks.
It is important to make cuts in the right place and not to defoliate the plant more than what should be considered in the growing season. If you do this, you can cut 365 days a year.
If you are going to do aggressive pruning, like with crape myrtle, you need to do it during the dormant season.
When it comes to flowering plants, there are so many things to consider, but there is a thing called the May Rule. If your plants bloom before May, prune them right after they bloom. This includes camellias and azaleas. For plants that flower after May, prune during the dormant season.
After you have made the cuts, do not put sealant on it. The healing process takes place chemically within the wood.
It’s actually walling off that area of dead tissue and keeping that decay confined to that particular area. What you do on the outside doesn’t matter.
Tree Health
How to ensure a healthy tree/shrub?
Billy: It really has a lot to do with the initial establishment of the plant, how that plant grows and progresses from the initial installment onwards.
My advice as an arborist is to make sure the soil is properly prepared and follow the spacing guidelines.
What are the reasons for poor tree health?
Billy: In terms of tree health, the first thing I see is root damage, especially in mature trees. Whether it’s compaction, root cutting, slope changes, or water flow changes, all of these things will have a negative effect on the tree.
Mature trees are much less tolerant than smaller trees when it comes to caring for their roots.
How much damage can a tree’s root system take before it starts to damage the tree?
Billy: It’s subjective. People ask me all the time “how many of these roots can I lose and keep the tree?” The answer is, I can’t tell you.
The easiest way to explain it is to imagine a dinner plate. The dinner plate is all nutritious tree roots. Then imagine a wine glass with a stem. The base of that stem is the structural root plate of the tree. You can lose a lot of dinner plates and the wood is still structurally sound.
As for health, it depends on how many dinner plates it loses how the tree survives and thrives, and that’s a very difficult question to answer.
I suggest having a qualified arborist look at the tree and give you an estimate as every location will be different and every tree will be different.
My general answer is save as much as you can.
Garden beds around trees
What do you think about placing a raised garden bed around a tree trunk?
Billy: You don’t want dirt to build up around the tree in any form. There are certain levels of tolerance, depending on the type of soil you are working on.
Sand is more porous so you can get more sand on top of the roots than clay.
It’s all about air infiltration to the roots of the feeder. They have to have oxygen and if you put a bunch of dirt on them, they will suffocate and then the tree will fail.
Keep the taproot (where the first main roots attach to the trunk) open. When you see trees that look like pencils coming out of the ground, it means that the taproot has been buried.
Where to find an arborist
There is a science behind what we do. Without knowing how to do this, it is impossible to achieve proper maintenance or health strategies. Go to treesaregood.org to find a local arborist.
Further reading