In the Garden
Ralph Purkhiser, Purdue University Master Gardener
In a recent column, I mentioned a pollarded tree in my landscape, but did not give a lengthy explanation about pollarding. That has generated several questions this week, so I thought I would write about some of the trimming methods used in the landscape trade.
Tree topping has long been a method used to control the height of trees. Utility companies used to top trees along their rights-of-way (That is the correct plural.) Men working from bucket trucks would cut off the upper branches of trees to make them shorter than the adjacent utility lines. Sometimes, people would also hire tree trimmers to top other trees in their lawns, often fearful of large trees towering over their homes and other buildings. The problem is that topping usually creates more problems than it solves.
Indiscriminately cutting the branches to a particular height means that many, if not most, of the cuts will not be at branch junctions. That means there will be many stick-ups left in the tree canopy. When a tree is properly trimmed at the collar near a branch junction, the tree is able to heal itself. Stick-ups do not heal quickly, inviting insect damage and disease to enter the tree. New growth also becomes a problem. Junction cuts, since they scab over quickly, do not usually result in new growth. Stick-ups will sprout new growth, which is usually straight up and spindly. Within a few years, that growth will reach the utility lines and the whole process must be repeated. The new growth is also usually weak, so the branches often break in the wind and fall. When people top trees near their homes because of fear of falling branches, they actually increase the likelihood of falling branches from the re-growth.
There are good reasons for removing part of a tree’s canopy, but it should be done by an arborist who knows to cut branches only at branch junction cuffs. Removing dead or damaged branches or branches that are rubbing against a structure will improve a tree’s appearance and make it safer, it the trimming is properly done.
Coppicing and pollarding are really forms of tree topping, but are done for specific reasons. In medieval times, before crops like corn and soybeans were introduced to Europe, farmers often depended on trees to provide silage to feed animals through the winter. Wood was also a common heating fuel and was used for construction. Many utensils used in everyday life were often carved from wood. Soon, the demand for wood products was greater than natural forest growth could supply. They noticed that some trees would re-grow from the stumps left after cutting a tree. That re-growth was usually straight, making it good for posts and building materials for boat construction. Harvesting during the summer also allowed farmers to make silage from the leaves of the re-growth, and thus the practicing of coppicing was born. Land owners would harvest an area of coppiced trees on a regular rotation, usually every two to six years for animal feed or every eight to ten years for wood, depending on the species and the planned use of the wood.
Coppicing had some drawbacks. If one pastured animals in the woodland, they would eat the leaves before they could be harvested. That gave rise to the practice of pollarding. In pollarding, the original trees would not be but to near the ground. Instead, stubs would be left tall enough to keep the animals from grazing the canopy. Wood lots managed by regular harvesting may supply livestock food and wood for many years, but the trees must have regular attention.
Eventually, someone decided to coppice and pollard trees to produce a particular look in the landscape. Many European grand estates have lanes lined by pollarded plane trees, looking like rows of lollipops along the lane. Maintaining such a look requires a lot of work.
Next week, we will explore some other trimming techniques used to produce ornamental trees.