The controlled lowering of tree limbs, often called rigging, is a technical process used when a branch cannot be safely free-dropped to the ground. This technique is necessary to protect nearby structures, sensitive landscaping, or utility lines from impact damage. Rigging involves attaching ropes and specialized hardware to a limb before it is cut, allowing its weight and descent to be managed and controlled by a ground crew.
Pre-Lowering Safety and Equipment Assessment
The process of rigging a limb begins with a thorough site and equipment assessment. Every person involved, especially the ground crew managing the ropes, must wear appropriate Personal Protective Equipment (PPE) to mitigate the risks associated with falling wood and high-tension lines. This gear includes a protective helmet, safety glasses, hearing protection, sturdy, slip-resistant boots, and cut-resistant gloves to maintain a secure grip and guard against abrasions.
Before preparing the rigging system, the team must assess the tree’s health and the limb’s characteristics, including its approximate weight. Arborists calculate weight by factoring in the limb’s volume, diameter, length, and the species-specific green wood density. This weight estimate is crucial for selecting rigging hardware with the appropriate load rating and for establishing a clear drop zone that is free of obstacles.
The necessary tools must be staged and ready, including a sharp saw and static rigging ropes designed for high strength and minimal stretch under load. Slings or webbing are required for anchoring hardware to the tree. The system relies on specialized friction devices or secure points for controlling the rope’s movement.
Establishing the Rigging and Friction System
The selection of a robust anchor point is the foundation of a safe rigging operation, as this point will bear the entire dynamic load of the falling limb. An ideal anchor is a strong, stable point in the tree trunk, or an adjacent, exceptionally sound limb situated directly above the piece to be removed. Arborists often use a block and pulley system attached to the anchor with a wide sling to reduce friction and distribute the load over a greater surface area of the tree bark.
The rigging rope is then attached to the limb that will be cut, typically using a specialized knot like a running bowline or a secure girth hitch with an eye-spliced rope end. This attachment, known as the choke or wrap, is generally placed about three inches away from the intended final cut location, ensuring the rope will catch the limb immediately after it is severed. The rope is run from the secured limb, up through the anchor point, and then down to the ground crew.
Friction management is the mechanism that allows the ground crew to control the enormous force of a falling limb. This control is achieved by running the lowering line through a friction device or by wrapping it around a solid object at the base of the tree. Specialized lowering devices, such as a Port-A-Wrap or a capstan-style bollard, are designed to create consistent friction, allowing a single person to manage loads far exceeding their body weight.
The ground crew manages the rate of descent by carefully applying tension to the running end of the rope. By adding or removing wraps around the friction device, they can precisely regulate the speed at which the limb is lowered. This controlled application of friction dissipates the energy generated by the falling mass, transforming a sudden shock load into a smooth, manageable descent. The friction device, or a secure wrap around the tree’s base, must be anchored low and firmly to the trunk to maintain stability.
Execution: Making the Cut and Managing Descent
The standard technique for removing larger limbs is the three-cut method, which prevents the bark from stripping down the trunk when the weight of the limb breaks away. The process begins with an undercut, made on the underside of the limb and extending about one-third of the way through its thickness.
The second cut, known as the relief cut, is positioned further out on the limb, past the undercut, and is cut from the top all the way through to remove the bulk of the limb’s weight. This sequence ensures that when the limb breaks, the initial undercut intercepts the tear, preventing the bark from peeling down the main trunk. The third and final cut then removes the remaining stub, or collar, right outside the branch bark ridge, promoting the tree’s natural healing process.
Clear and constant communication is mandatory between the person making the cut and the ground crew who will be managing the rope. A pre-arranged protocol of verbal commands, hand signals, or radio checks must be used to ensure everyone is ready before the final severance is made. Standard verbal commands like “Clear,” “Coming in,” or “Headache” serve as audible warnings.
As the limb is cut and its weight transfers onto the rigging line, the ground crew immediately manages the descent by slowly releasing the rope through the friction system. They maintain a firm but controlled grip, allowing the rope to pay out gradually, which slows the limb and guides its trajectory toward the designated drop zone. The limb is lowered completely before the ground crew secures the line and prepares the system for the next section of wood.