Questions and Answers

The following are questions answered by Brian W. Sayers Ph.D. Certified Arborist
and Jeremy P. Sayers M.S. Certified Master Arborist


Does the recovery time between Coniferous and Deciduous trees differ when a wound is made?

Depends upon the tree species. Faster growing trees recover more quickly. Late fall to early spring is problematic for deciduous trees as they cannot respond to wounds when dormant. Trees don’t “recover”, they adapt through the formation of wound wood or callus wood and through CODIT. The most important factor is how healthy the tree was to begin with.

Would a wound hole affect branches that fall in line with that vascular tissue

Very marginally.  The tree is better at moving material vertically, but it can and will move around a problem area as well.
The “marginal” part can vary depending on the diameter of the hole, proximity to the branch union and how many holes are in line with the branch.

Do you attract pests and /or disease by creating an opening in the face of the tree?

You DO create an opening for fungi (not attract) but you can forestall most problems with Lac Balsam and by avoiding dormant season “wounds." Any wound will cause a tree to release chemicals that will attract insects however, a healthy tree will repel these attacks successfully.

Does the use of steel hardware that has been treated with zinc or cadmium plating vs. raw steel or stainless have an adverse effect on tree health?

Not very likely. No research definitive on this. Should use hardware that is specially manufactured for treated wood.

What sort of impact does foot traffic have around the root base of the tree?

Probably the most damaging. Can be severe, especially if ground is saturated. Two – four inches of wood chips applied BEFORE construction will help prevent. Chips should remain. The significant area = 1 foot of radius for each inch of diameter. So, a 12” diameter tree will be sensitive to compaction from the trunk out to 12 feet. The drip line is another good guideline to use for establishing a TPZ (tree protection zone). 

Do trees react to added weight? If so, how?

Trees will grow additional wood at any stress point. Significant vertical weight will increase flare at base. Weight that increases lean stress requires a couple of years before the tree resolves its stress. Added weight changes a tree’s center of gravity and increases wind shear. A tree will respond as stated above over several years (if it’s healthy) but will be more likely to fail during this adjustment period.

Do trees communicate with each other when they are under stress? If so, how?

Rarely. They communicate (when they do) by exchange of chemicals which carry signals. In some cases one tree will supply nutrients to another. Requires prior root grafting by the trees. This is emerging science and very little is known with certainty. Some recent research out of Germany does point to the idea that trees will “warn” each other when stressed.

Do younger trees heal faster than older trees?

Yes. However, “heal” is not best term. "Respond to wounding" is better. Younger trees may respond more quickly but are also more prone to a wound being catastrophic or deadly.

Would the time of year due to temperature change have an effect on when you build in the trees? Are trees under more stress during different times of the year and would that have an effect on when or if to build in them?

Not just temperature change. Water deficit increases stress significantly and greatly reduces recovery time. So, often temperature affects water availability. Any tree that is dormant cannot respond to wounds.

Would trees benefit from fertilization prior to construction? If so, how long before?

Some benefit. Not most important factor. Use low N fertilizer. Tree conversion of fertilizer to usable materials takes at least one season. All “yard” trees benefit from fertilizer since we remove fallen leaves and branches that would normally return nutrients to the soil through decomposition. Also, yard trees have higher nutrient needs due to competition with turf and other yard-related stressors. The correct fertilizer at the proper time is critical.

Would you recommend annual fertilization after the completion of a treehouse?

Yes. But low N. A better recommendation would be a full after-care program involving inspection and then pruning/fertilizing/spraying as needed.

Could reflective material have an effect on the health of the tree i.e. steel roofs or glass?

If these constructs increase significantly the overall amount or focus of the sun’s rays, that can kill bark. If no other significant changes (loss of canopy, removal of adjacent trees) then the constructs would not be problematic.

Does a treehouse attract more pests to the tree?

Not at all. Any stressor has the potential to attract pests. A treehouse may also create new places for pests to lay eggs, overwinter, etc.

Is there a way to measure the density of the tree without taking a core sample?

Some high tech devices can do this. However, there is no reason not to take a core sample. Sounding with a rubber mallet works well with practice.

Given that older trees grow faster than younger does that make them better candidates for treehouses? (Nate Stephenson)

Older trees grow MORE SLOWLY than younger trees. The growth rate of an older tree will be largely irrelevant to construction of a tree house in it. Older trees eventually go through a process called “re-trenching”. During this process a tree may “shrink” by killing off branches. This could create hazards sooner than in a younger tree. Also, a younger tree will typically produce more wound-wood more quickly.

How does a trees growth habit change due to a structure being built in them and would they adapt to grow around or through the interference?

Trees will adapt to a treehouse construction. If major limbs are removed this will affect the growth habit of the tree. It may, for instance, produce adventitious growth. It will attempt to replace lost canopy and it will divert its resources to producing “stress” wood. Tree morphology is largely genetic and will not be altered due to human interference. However, a tree is hardwired to change its growth if the amount of sunlight or moisture is changed. Both of those things are possible from the treehouse interference alone but are likely very minimal. As the tree continues to grow it will engulf the treehouse by growing wood over the hardware will push against any part of the treehouse in contact with the trunk or limbs. The tree will eventually win.

What is your overall feeling about building in the trees? 

Make sure tree is healthy first.

Prevent soil compaction. Remove few, if any, large limbs. Do not girdle anything. Otherwise will be no problem for a healthy tree. The fewer points of contact with the tree the better. Make regular inspection part of the culture. Involve a certified arborist, especially pre-build. The lower the treehouse is attached to the tree (s) the less likely you are to have issues (low wounds “heal” better, high attachments create stress points by making the tree rigid where it is supposed to be flexible).