Melbourne’s Grand Old Trees
What would the grand old trees of Melbourne Gardens say if they could talk? These historic and in some cases remnant trees have witnessed the evolution and growth of Melbourne and require a little special TLC as they age.
Two stand out specimens include the majestic Araucaria bidwillii (Bunya Bunya Pine) planted in 1897, and the iconic Lions Head Tree, a River Red Gum (Eucalyptus camaldulensis) which was most likely a sapling when, in 1835, a squatter camp was set up on the bank of the nearby Yarra River, which eventually developed into the City of Melbourne. These biological treasures have developed unique aging characteristics, ranging from hollows and bark fissures to large volumes of dead wood and complex canopy structures that form micro-ecosystems and enable them to support a myriad of species who rely on them for food and shelter. With advancing age, the soil environment of these large old trees steadily increases in ecological richness, benefiting surrounding flora and providing a home for the wide range of microorganisms and insects living within the soil and roots.
At Royal Botanic Gardens Victoria, various strategies are undertaken to enhance the longevity of large old tree specimens that fall within the realm of ‘conservation arboriculture’. These include specific pruning methods employed for old trees which are designed to imitate the slow, natural contraction of the crown that occurs as they reach great age. Typically, the tree's outer canopy is gradually shortened via several small dose pruning events that are implemented over many years - even decades. This method of restoration, sometimes called retrenchment pruning, aims to rejuvenate the tree’s crown, and improve health and structure.
This is currently being practiced by the Garden's arboriculture team using lightweight, easy-to-manoeuvre STIHL battery pole pruners to restore one of the ancient River Red Gums in the Melbourne Gardens known as the Cockatoo Tree, following the trauma of losing a large portion of its crown during high winds in 2013. The arboriculture team is working on this tree’s structure and health so that the Cockatoo Tree can continue to sustain and enrich biodiversity for years to come.
Another technique practiced by the arboriculture team is pollarding, which is used to control tree size and form and has an additional benefit of enhancing tree longevity. Pollarding is practiced on trees of every age but must commence while the tree is young and involves the periodic (often annual) removal of the upper branches of a tree. The technique dates back as far as Neolithic times and was used historically to produce firewood, feed for livestock, and more, with the advantage of not killing the tree. The practice produces a striking knuckled appearance, which is visible on an Erythrina crista-galli (Cockspur Coral Tree) specimen growing in Melbourne Gardens, which is pollarded using STIHL Battery chainsaws.
This careful work ensures these special inhabitants of the Gardens will live through the further evolution of Melbourne and continue to play their part in supporting the life of the Gardens for many years.