Do Treehouses Damage Trees?
14th July 2014
Today, we’re going to be looking at the impact treehouses can have on trees, as well as the methods by which we can reduce this impact.
Put simply, a treehouse will inevitably cause a certain amount of stress to a tree, and attempting to design a treehouse without sufficient understanding of tree anatomy can lead to problems. However, as living organisms, trees have ways of protecting themselves and recovering from damage. By understanding the mechanisms that a tree uses to protect itself, we at Blue Forest keep the impact on the tree to an absolute minimum, and cause little to no lasting damage.
The bark of a tree performs a very important function. Being that trees are alive, they are vulnerable to diseases caused by bacteria and viruses. Generally, these are a much greater threat than some instance of physical trauma, since a tree can survive the loss of its limbs but a disease can kill the entire tree.
Since trees don’t have an immune system as such, their only real defense against bacteria and viruses has to come from physically preventing the microorganisms getting in. Bark is this physical barrier, and thus any place where the bark is damaged and the living tissue is exposed is like an open wound. Thus, keeping bark damage to a minimum is key to protecting the health of a tree.
Cutting chunks or branches out of the tree is therefore to be avoided. Slices like this expose a great deal of the interior of the tree, making the risk of disease great. You should also preferentially use one larger bolt instead of several smaller ones where possible; the fewer holes made in the bark the better.
Also, avoid using ropes in most cases. A rope will actually cause damage to a large surface area of bark as the tree slowly moves and grows, and constantly has the friction of the rope rubbing on it. Ropes generally do greater damage than bolts in the long run, so if ropes are a necessity for your design, make sure you remove them once a year to alleviate the pressure and reduce damage done to the bark. Particularly if your design includes ropes, it is strongly recommended that you invest in professional assistance with your tree house, since incorrect usage of rope supports can lead to strangulation of the tree.
As mentioned above, trees don’t have immune systems, and they also don’t really have a method of regenerating tissue in the way animals do. Instead, a tree’s response to trauma is to wall off the damaged area and allow it to die in a process called compartmentalisation. The tree then doesn’t waste nutrients on supplying the damaged area, and continues to grow elsewhere.
Be aware then, that a tree does not ‘heal itself’ as such, and any impact on a tree will be permanent. Understanding the mechanism of compartmentalisation and how to minimise the amount of area that a tree walls off is important to knowing how to build a treehouse with minimal impact on a tree’s health.
One of the most important principles here is to reduce the number of punctures into a tree. Don’t use nails and screws to attach materials to the trunk, and instead rely on a few large bolts for support and save the screws for holding the structure together.
Perhaps even more importantly, make sure your punctures are spaced out a good distance. If there are too many punctures within a certain area, the tree may compartmentalise the whole area, meaning you’ll be killing the area between the punctures instead of just the small areas around each puncture. A good policy is to maintain 12’’ of horizontal and vertical distance between each puncture.
Trees use roots not only to absorb nutrients from the soil, but also to anchor themselves into the ground. The roots of a large tree will form a very extensive network and go quite far underground in order to allow the tree to support its own weight and to remain stable in the wind.
Often, trees will not grow directly upwards but will lean heavily to a particular side, and in this case the roots will grow in a particular way to compensate for this. Whichever way the tree is overbalanced, the roots will grow in the opposite direction to act as a counterbalance.
However, this is a very gradual process, and happens as a tree slowly grows in one direction. A treehouse, even if built over several months, is still going to be a very sudden addition of weight, and it will take the roots many years to grow to compensate. Whilst in this weakened state, a tree’s resistance to storm damage will be significantly lessened.
Consequently, weight distribution is very important when building a treehouse. As much as possible, try not to add too much weight to a particular side of the tree. Circular designs that wrap around the trunk are a particularly elegant solution here, as they will keep most of the weight at the centre of gravity of the tree. It also worth considering splitting the weight of the treehouse between several trees if possible, as this will significantly reduce the problem.
Trees never really stop growing. After a tree reaches maturity, the rate of its growth will slow down dramatically, but nevertheless it will not completely stop. You should be aware of this when building a treehouse.
If supports are particularly close to the tree, the tree will eventually grow around these supports. This rarely causes actual damage to the tree, but be aware that this will result in a disfigurement to the tree, and it will obvious if the treehouse is removed where the tree had to grow around a previous obstacle. As such, you should try to make the supports as unrestrictive as possible, giving the tree room to grow.