Fact Sheet: Managing Tree Populations
Presenter: John Patrick, 15/08/2009
SERIES 20 Episode 29
Trees are a remarkable part of our urban fabric. They provide shade, colour, texture and variations in scale. Trees, like people, pass through different life stages - juvenile, immature, mature, adult and senescent. It's easy to think that trees live forever but senescing trees are those that are over mature and at the stage of decline. To ensure there are plenty of trees around for future generations to enjoy it's important that tree populations be managed properly.
Melbourne's Fitzroy Gardens is approximately a hundred years old and many of its trees are becoming senescent. A number of challenges will need to be faced over the next few years when it comes to replacing them.
Identifying Senescent Trees
- The development of epicormic growth throughout major branches. This means that buds on the trunk which usually lie dormant begin to grow quickly and in a cluster in an attempt to get as much energy into the tree as possible.
- Over-production of fruit as the tree tries to reproduce itself before it dies.
- Severe pest infestations are common.
- Drying out through over-exposure in hot dry summers.
- Weak branches that are blown down by the wind.
Many of our large parks are a reflection of past tree management practices where little thought has been given to the future of the park in regards to the trees.
Fitzroy Gardens contains three to four hundred trees and about eighty percent of those are in the latter part of their life. Over the next twenty years those trees will probably need to be removed.
Tree Management Principles
- An ideal aim would be to plant trees successionally like any other crop. If we consider that trees might live for a hundred years, we ought to aim to have ten percent of them in each of the following age groups - nought to ten, ten to twenty, twenty to thirty etc, so that around ten percent of the trees will be recently planted, and ten percent of the trees will be coming towards the end of their lives.
- If whole rows are senescent consider replacing the whole row, rather than just the worst affected trees. This will keep the avenue affect intact when the new trees grow.
- It's also been recognised that inter-planting new trees amongst mature trees can cause problems such as root competition and competition for light. At Fitzroy Gardens a whole avenue has been removed and a complete new planting established. These will grow together to form a wonderful mature avenue in another twenty or thirty years.
- One of the greatest problems of park management is that people object to tree removal, despite the fact that it provides opportunities. New trees can be planted that develop quickly, delivering a great impact within the first ten years.
John suggests, "When your council are developing new plans for your local park, get involved. Understand the issues and help contribute to the selection of trees for your park. It will benefit you as well as future generations."
Information contained in this fact sheet is a summary of material included in the program. If further information is required, please contact your local nursery or garden centre.
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