Living proof

There are few places where you can observe the interplay between steel and living trees better than at the Out'n'About Treehouse Resort with its 15 treehouses, huge climbing forest, suspension bridges, zip lines and a total of over 50 platforms. This legendary place in Oregon, USA, is both the birthplace and a kind of museum of modern treehouse construction.

For over 30 years, a wide variety of attachment methods have been tried and tested on trees: threaded rods, steel beams, clamp constructions with wooden beams, rope fastenings... The first modern treehouse bolts were also developed here: ‘Garnier Limb’ and ‘Treehouse Attachment Bolt TAB’.

Here you can see the first attempts at tree fastenings for treehouses:

Response to wounds

With ‘damaging’ attachment methods such as tree bolts, a hole is first drilled into the tree and the bolt is screwed tightly into it.

Such injuries are nothing unusual for trees – they have spent millions of years specialising in dealing with branch wounds, crown breaks, lightning strikes, rock falls and other injuries.

Healthy trees react immediately: they store resins and oils to seal the wound and protect it from rot. The wound is then covered with special reaction wood.

Do fungal spores enter/exit through the borehole?

Fungal spores can enter the tree or escape from the core through drill holes in the tree. When installing a tree bolt, the tool should therefore be thoroughly disinfected and the drill hole quickly sealed with the bolt.

Here too, the tree recognises such injuries and reacts according to the CODIT principle (Compartmentalisation Of Damage In Trees - Alex Shigo):

The tree actively fights the fungal attack. In the case of open wounds, it first reacts to the ingress of air (air embolism) and then protects itself from rot by forming sealing walls made of antifungal substances.

Does a treehouse harm the tree?

Not at all! A global survey Source: Bachelor thesis by Onja Johannes Hardorp, 2017, HNE Eberswalde of 18 professional treehouse builders (including Pete Nelson, Alain Laurens and Andreas Wenning) shows that

out of 2,253 treehouses, only two led to the death of the tree – less than 1 per mille!

Treehouse-Pro Johannes Schelle even raves about his 13-year-old treehouse (see picture) – his two trees, a beech and a lime, always bloom two weeks longer than all the others in the garden.

One thing is clear: if you choose the right tree and fasten the treehouse to the tree in a way that protects it, you have nothing to worry about!

Living proof

This concern disappears when you realise how adaptable and resilient mature trees (ø > 30 cm) are. Those that have survived the difficult years of growth have already demonstrated enormous vitality.

Trees face many challenges in the course of their lives – from extreme weather events such as droughts, storms, hail or frost to human intervention such as soil compaction, root damage or improper pruning.

However, thanks to large energy reserves from carbohydrates and fats, as well as a structure that far exceeds daily stresses, healthy trees are well equipped to cope with such extreme situations. No wonder they are among the oldest organisms on Earth!

Incorrectly secured – the tree MUST be able to grow!

We understand the initial concerns all too well – we too were reluctant to drill into trees at first and looked for ‘damage-free’ alternatives to treehouse fastenings. Like many other treehouse builders and climbing forest operators, we used to rely on steel rings and clamping beams to protect the tree.

But about 10 years later, we all realised that these methods are anything but sustainable, as trees grow surprisingly quickly in width (3–15 mm per year).

The long-term consequences?

Squeezed trunks, interrupted nutrient supply, dangerous breaking points – and on top of that, expensive maintenance work and dissatisfied customers.

The modern solution: Tree Bolts

How do you attach a heavy construction to a tree without damaging it?

This requires long-term thinking: we need a fastening technology that can bear enormous loads and still allow the tree to grow unhindered in width.

The solution: tree bolts

Thanks to pioneers in the USA Michael Garnier, Pete Nelson, Charles Greenwood, ..., we know that trees and tree bolts work together perfectly for decades.

All you need is a healthy tree that is thick enough!