Pollarding is an ancient pruning technique used to maintain trees at a set, manageable height, often seen in urban and formal landscapes. This method involves the systematic removal of upper branches to promote a dense head of new foliage. Historically practiced across Europe for centuries, pollarding effectively controls the tree’s overall size.
Defining Pollarding and Avoiding Topping
Pollarding is often mistaken for topping, an aggressive and destructive form of pruning, but the two methods are fundamentally different. Pollarding is initiated on a young tree by making precise, repeated cuts back to the same point on a main branch or trunk. Over time, these repeated cuts cause the tree to form a swollen, permanent structure called a pollard head, or “knuckle.” This knuckle is a mass of protective wood tissue that allows the tree to quickly seal over the small annual pruning wounds, a process known as compartmentalization.
Topping, conversely, is the indiscriminate cutting of large branches at random points, typically on a mature tree, to reduce its height. This practice creates large, unhealable wounds that leave the tree highly susceptible to decay and disease. The tree’s response is to sprout numerous weak, upright shoots called waterspouts, which are poorly attached and create a future hazard. A successful pollard requires the initial cuts to be made when the tree is young enough to develop the protective knuckle and tolerate the severe canopy reduction.
Selecting Appropriate Tree Species and Timing the Cut
Pollarding requires the ability to regenerate vigorously from old wood, meaning not all tree species can tolerate the technique. Species known for their robust sprouting capability respond well to this method:
- London Plane
- Willow
- Linden or Lime
- Maple
- Hornbeam
- Oak
- Ash trees
Conversely, most conifers, such as pines, spruces, and firs, should never be pollarded. They lack the necessary dormant buds to produce new growth from old wood, which leads to dieback and tree death.
The timing of the initial cut and all subsequent pruning is important for the tree’s long-term health. Pollarding must be performed during the dormant season, between late winter and early spring, before the buds begin to swell. Pruning during this period minimizes stress on the tree and reduces the risk of fungal pathogens entering the fresh wounds. The tree’s energy reserves, stored in its root system, are immediately available to fuel the burst of new growth once the growing season begins.
Establishing the Initial Pollarding Cut
The initial pollarding cut establishes the permanent height and structure of the tree for decades. This process requires sharp, clean tools, such as a pruning saw or bypass loppers, to ensure precise cuts that heal quickly. The desired height of the pollard head is selected for long-term management, often ranging between six to thirteen feet (two to four meters) above the ground.
To begin, cut the central leader, the main vertical stem, at the chosen height, followed by the surrounding lateral branches. The goal is to cut the main branches back to a small stub, made just above a lateral bud or branch collar to encourage the formation of the first knuckle. This severe initial cut creates the scaffolding from which all future growth will emerge. Ensure cuts are clean and do not tear the bark, preventing large wounds that could compromise the tree’s defense systems.
Long-Term Maintenance of the Pollard
Once the initial structure is established, the technique requires ongoing maintenance known as re-pollarding. This involves cutting back all the new, vertical shoots, commonly referred to as whips or waterspouts, that emerge from the pollard head. The frequency of this cutting varies based on the species and desired aesthetic, but it is performed every one to three years during the late winter dormant period.
During re-pollarding, every new whip must be pruned back precisely to the top of the established knuckle. Care must be taken never to cut below this hardened point, as the knuckle contains the tree’s protective callus tissue. Cutting into the knuckle would expose older wood to decay, effectively turning the pollard into a topped tree. Maintaining this schedule prevents the whips from becoming too large and heavy, reducing the risk of them tearing out during a storm.