Steel in the tree
Do nails, screws and other steel parts damage the tree?
You want to attach something to a tree: a small sign, a birdhouse, a swing beam, or as in our case, a whole treehouse. Then you are quickly confronted with the statement:
“Screws are harmful to the tree! Just one copper nail is enough, and the whole tree will die!” — is that true?
Many people are initially unwilling to hammer a steel part into a living tree – understandably so. But is a small hole really a danger to the entire tree? How does the tree tolerate the alien steel object? Are screws or clamps the better fastening method? Are there alternatives?
Here we go into more detail about the concerns (with a special focus on tree house construction):
1. Concerns – steel is not compatible with the living tree?
Examples of steel-wood interaction (Old treehouse fixings, Garnier Limbs, Out’n’About Treehouse Resort, 2016):
The combination of steel and wood harmonises perfectly! There are no indications that steel, stainless steel, copper or other alloys would harm the tree or “poison” it through detachment (e.g. rust).
Evidence for this are e.g. the treehouse constructions of Michael Garnier in the USA, which are more than 20 years old. Numerous experiments show: the tree does not repel the steel, but envelops it, fully integrating it into its living situation.
2. Concern – Nail, steel screw and bolt damages the tree?
Every nail and every borehole are damage in the tree, but trees know how to deal with this kind of injury very well – it is similar to a branch break:
The hole cuts off some water and nutrient lines. Immediately afterwards, the tree begins to heal the wound by selectively storing resins and oils to seal the wound. In the following years, it will form extra-strong reaction wood at this point. Thanks to its enormous energy reserves, the tree can easily cope with such situations.
The difference of a wound from a Tree Screw versus a branch break: The wound is immediately closed again with the screw – so no insects or fungal spores can get in.
3. Concern – The tree will suffer in the long term from the treehouse?
This worry is lost when one knows how adaptable and resistant mature trees are. If a tree has survived the difficult years of growth, that alone is proof of its incredible survival power.
In the course of their lives, trees are repeatedly confronted with injuries and problems. These include natural influences such as:
Forest fires, droughts, permafrost, floods, avalanches, lightning strikes, branches breaking off during storms and snow, loss of leaves due to hail, fungal and insect infestations, …
But also damage caused by humans:
Car crashes, root damage during earthworks, cut-off of water supply by new buildings, compaction of the soil and thus lack of oxygen supply for roots, damage by neighbouring felling operations, …
A vital tree can cope well with such extreme situations, as it has large energy reserves (carbohydrates & fats) in its adult state. Its entire structure is designed to withstand many times its daily stress. It is not for nothing that trees are among the oldest living creatures on earth!
Trees are true masters of survival and know how to adapt quickly to new situations: Treehouses are the perfect example of this!
A survey of 18 professional treehouse builders showed that out of 2253 treehouses built, only two trees died as a direct result – that is far less than 1 per thousand. (Source: Bachelor thesis by Onja Johannes Hardorp, 2017, HNE Eberswalde). Treehouse professional Johannes Schelle raves about his treehouse, which he bolted to a beech and a lime tree 12 years ago: “The trees have a magnificent crown and bloom every year for a fortnight longer than all the other trees in the garden.”
The base for a sustainable treehouse is, of course, the right fixing method.
4. Concern – Why screws at all, aren’t “injury-free methods” inherently better?
Even so-called “injury-free” fixings (clamping technique, cuffs, ropes) can damage the tree. As no direct wound is necessary, they seem harmless at first – the damage only becomes apparent in the following years!
This is because trees grow in width (thickness growth, annual rings): as a tree gains 2 – 15 mm in diameter every year, clamping procedures sooner or later lead to constriction and bruising. The nutrient-conducting tissue under the bark is squeezed off, the sap flow comes to a standstill and, in the worst case, dangerous predetermined breaking points develop (see pictures).
Large-scale bruises and constrictions are ultimately more damaging than the punctual injury caused by a screw.
For large, static installations such as treehouses, high stands or platforms in the climbing forest, you should inform yourself well in advance about the fastening techniques. The aim is to make these constructions permanently safe and tree-friendly!
5. Conclusion – Green light for Tree Screws
Attach small objects to the tree with nails and wood screws:
Single nails and small screws will not harm a mature tree. Objects such as signs, fence posts and barbed wires are wrapped around by the tree and thus become an integral part of its living situation. If resin oozes out in the process, this is just a natural sign that the tree is reacting to the wound.
Attach large objects to the tree with special Tree Screws:
In our treehouse carpentry “Baumbaron” we have been gathering our experience with various treehouse fixings for over 13 years and 250 successful treehouse projects – our conclusion:
- Trees integrate steel objects into their living situation.
- In order to avoid damage to the tree in the long run, flat crushing should be avoided.
- Special “Treehouse Screws” (also known as: ‘Garnier Limb’, ‘Treehouse Attachment Bolt TAB’ or ‘Tree Fastener’) are used to keep wooden beams at a distance so that the tree can continue to grow undisturbed.
- Normal wood screws from the DIY store are not suitable for fastening a treehouse, as they are not designed for the high load.
- The injury / contact area should be as small as possible, and the tree should be able to easily wrap around the foreign body.
Screws do not harm the tree, quite the opposite: Treehouse Screws have established themselves worldwide for over 20 years as the safest and most sustainable fastening technique and are an indispensable part of modern treehouse construction!