Felling trees is a dangerous job. It’s really not as simple as taking a chainsaw to the base of a tree and letting rip. Tree felling requires serious planning if we are to avoid damaging nearby property or injuring people. So, how are trees taken down? This depends on where the tree is and how big it is. The plan to remove a tree will incorporate lots of different aspects in the plan – nearby buildings and roads, utility lines and landscaping. Arborists also use a whole kit of special equipment like ropes and rigging to help them with their job. Here are some of the considerations arborists make when assessing a tree to be felled:

• The tree’s width, height and lean

• The intended direction of its fall (dependent on tree type, utility lines, buildings, landscape etc.)

• Fall zone clearance

Techniques for Taking Down Trees

Just as each tree is unique, so is the way it is removed. Different types of trees often require different tree felling techniques. A deciduous tree, for example, will have a wider tree canopy than a coniferous tree so the tree removal approach is often different.

Straight Felling

When removing trees, we often refer to ‘straight felling’. This means removing a tree as a single unit. This is only possible when the environment allows i.e. when there is enough space for the tree to be felled without causing any damage to property or landscaping nearby. When trees are removed using straight felling, arborists will control the tree’s removal by using guide ropes and wedges so that the tree falls in a way that is both safe and expected.

Sectional Felling

When a tree can’t be removed by straight felling (if, for example, there isn’t a lot of space surrounding it), then a technique called sectional felling is used. This means that the tree is removed in sections so that there is no damage to surrounding obstacles like utility lines, roads, buildings or landscaping.

When doing a sectional felling, there are many different techniques and methods used. As always, these are adapted for each unique tree, which makes expert knowledge and experience essential.

Tree felling with sectional dismantling means that a skilled climber will often need to climb up the tree to secure an anchor point. The climber will then abseil down the tree to work on the lowest limb first, working his or her way up the tree. Sometimes, rigging equipment is also needed.

Tree Rigging

This is the art of sectional felling using blocks, pulleys and ropes to aid in the dismantling of trees or parts of trees. Rigging equipment incorporates a whole host of various equipment and often needs extensive knowledge of equipment, rope types and strengths, wood properties and physics. As with all tree work, communication is also essential between workers when on site.

The Basics

Tree rigging has a range of complexities. Even a simple rope thrown over and attached to a branch is classed as basic tree rigging. People on the ground will hold onto the end of the rope while the arborist is tasked with cutting off the branch. The person on the ground will guide the branch to the ground. This basic technique of tree rigging is one of the oldest and simplest in existence. It relies on the person on the ground being strong enough to hold the branch’s weight. The climber also needs to have the ability to judge the weight of the branch to ensure the rope is the right strength. There are variables too that make this task even more of a challenge. This includes the friction between the branch and the rope as well as the force applied by the person on the ground.

High-end Tree Rigging

While the basics are simple enough, there are high-end tree rigging techniques too. Modern tree rigging often uses high modulus poly ethylene (HMPE) ropes. These ropes don’t stretch at all! Other modern pieces of kit include pulleys that are almost frictionless, capstan winches on lowering bollards that apply tension to 44:1 and laptops with hooked up dynamometers capable of calculating angles and cutting forces for tree branch removal where there is surround property or obstacles.

Techniques for Tree Rigging

There are many different ways to fell a tree and modern arborists will incorporate the basic tree rigging techniques all the way up to high-end techniques in their day-to-day tree removal work. Every tree-rigging situation can be made as simple or as complex as the arborists need but it’s worth remembering that tree felling is never risk-free.

Arborists have to recognise the large forces generated when removing and lowering branches and wood on ropes. Forces don’t just disappear; they have to go somewhere and are changed into sound or heat. If, for example, a branch section is lowered too fast and the wood is too heavy, ropes can melt and weaken. In a worst-case scenario, the tree might fail altogether with snapping and breaking sounds. Nowadays, with modern technology, it is rare for these things to happen as long as arborists are well trained in the safe removal of branches.

With modern tree rigging techniques, it is mainly the tree and the ropes themselves that act as shock absorbers to dissipate generated forces. If a tree has a structural issue then this will always be taken into consideration and if necessary, tree rigging will involve the use of a helicopter, hi-ab or crane. With correct forethought, well-planned execution of techniques, equipment and teamwork, there are endless ways to lower timber and branches safely and efficiently from trees.

Final Thoughts

An arborist’s job isn’t just a physical one! Tree surgeons need to know all about the laws of physics as well as mathematics when planning to remove trees. It’s a highly-skilled job that needs a lot of training – inadequate training and improper techniques can be very costly indeed, not to mention highly dangerous. It’s always best to call in the professionals!