Pollarding and pruning of trees is an ancient but little understood art

Municipal gardeners have been out in force in the past few weeks cutting back many of the trees in Athens’s streets and parks almost right down to the trunk. This is pollarding, or high coppicing, a technique practiced widely for centuries in other parts of Europe, where basket weavers traditionally cut off thin branches for weaving. It is also done in order to produce a dense mass of branches for aesthetic purposes, or to keep the trees small. In a few weeks’ time, new shoots and tender young leaves will appear in profusion, creating a mass of greenery that will grow into shady canopies for summer. In Athens, mulberry trees along city sidewalks are pollarded for functional reasons, according to the head of Athens municipality’s parks and gardens department, Dimitris Papademas, but he warned that it is not appropriate to pollard, or even prune frequently, every tree, or every species of tree. «Here because the sidewalks are so narrow, we pollard mulberry trees to keep them small so they don’t obstruct passing buses, for example,» he said. Another reason for pollarding is that because at the time when the trees were originally planted, no care was taken to choose varieties that did not bear fruit. «If we didn’t pollard the trees, the sidewalks would be slippery every spring with crushed fruit, which would also drop onto parked cars and pedestrians,» he said. With pollarding, the tree is cut back nearly to the trunk, in a framework established when the tree is young, with a swollen knob that forms at the base of each branch. The key is not to injure the knob, which is where the new shoots will grow. Pollarding begins on young trees, and once begun, should be repeated throughout the life of the tree. Papademas said that both pollarding and pruning has been overused in Athens. «Other species of trees, particularly along avenues such as Academias and Acharnon where the sidewalks are wide, should not be pruned every year or even every two or three years. Every 10 years is often enough,» he explained. «We have had a lot of conflict over this. We believe in implementing the international practice of allowing trees to develop freely as far as possible, but because of restricted space on sidewalks, and because the public demands it, we have had to do otherwise,» he said. As for the pollarded branches, in times past Gypsies used to come around and gather them up for basket weaving, or else they were used to make frames for erosion control. Nowadays, the municipality shreds the branches into woodchips, which are then composted for recycling into the soil. Pruning techniques Generally, trees should be pruned to remove branches that are in danger of falling off or touching power lines, to remove branches that are diseased, damaged, or crossing over other branches, rubbing against them and creating open «wounds» that can allow disease to enter the tree. Pruning also is used to enhance the natural shape of the tree, creating a strong structure, or to stimulate the growth of blooms. Young shoots from the base of the tree or low down on the trunk should be pruned off to promote growth higher up, but removing too many will prevent the development of a strong trunk. Some trees need regular pruning, but unfortunately, careless and random lopping off of branches can do considerable harm, providing entry points for disease, inhibiting growth instead of encouraging it, and spoiling the look of the tree. One guide to pruning says that for branches of under 5 centimeters in diameter, don’t hesitate to prune; think twice about pruning branches between 5 and 10 cm and for anything bigger, only prune if you have a very good reason to remove it. Otherwise, trees are better left alone. One form of pruning, known as topping, a method of controlling the height of a tree, is actually considered extremely dangerous for the tree’s survival unless performed by a trained arborist. The main thing to be aware of in pruning is to make a clean cut at the base of the branch, so as not to leave a stub which is not only unsightly and hazardous but will not «heal over,» and will encourage decay. Care should also be taken not to cut too far back and rip the tree’s bark. In her book «Mediterranean Gardening,» Heidi Gildemeister recommends substantial pruning for multi-stemmed trees that make a dense crown. «Taking out stems at ground level lets air circulate… Where crowns interfere with neighboring plants, it is better to take out a whole branch rather than snipping here and there. Each cut makes a wound, but one large cut is considered preferable to many small ones,» she writes. In an interesting footnote, Gildemeister refers to the Mediterranean practice of pruning trees according to the moon’s cycle: «Fenceposts, cut with the waning moon, are said to last forever. The same moon suits pruning of grape vines. Watch sap drip when cut with the rising moon.»