Hyde Park - New Hills Figs for Central Avenue
Background
Several of the Hills Figs in Hyde Park’s Central Avenue are diseased and have fallen over or been removed as they became dangerous and unstable. The avenue was planted in the 1930s and the trees are now reaching the end of their safe useful life span.
The Central Avenue tree replacement program is detailed in the Hyde Park Tree Management Plan (TMP) which Council adopted in December 2006. The TMP provides strategies for the removal and replacement of the Central Avenue in four stages over several years, with increasing tree sizes to be supplied at each of the four stages. The existing Hills Figs will be maintained for as long as they are safe and healthy, until the first stage of replacement planting that is expected to begin in 2013 with increasing tree sizes to be supplied at each of the four stages.
A tree supply contract to grow the replacement trees was tendered and awarded to Trees Impact Nurseries, in late 2007. 127 trees are required to replace the Hyde Park Central Avenue however, due to the significance of the project and in order to guarantee supply; a second group of trees (total 254) is being grown.
Growing Process
In January 2008, 500 cuttings were taken from two Ficus microcarpa var Hillii (Hill’s Fig) located near the Sydney Art Gallery and potted into “nursery tubes”. The parent trees were selected for their physical structure and vigour. The selected trees were free of branch inclusions, which is a genetic weakness inherent in some species that makes them prone to failure.
Growing foliar cuttings is a vegetative propagation method, used in the nursery industry, to produce trees of the same genetic makeup as the parent tree; they are also faster to establish than seedlings.
Cuttings were taken from the non-woody branch tips, cut to size, stripped of leaves from the lower section and planted into a growing medium. At all stages of development hygiene standards are strict, with the use of clean growing medium and the sterilisation of growing areas, tools and personnel, to stop the introduction of any disease pathogens. Cuttings are kept in a warm humid environment to encourage rapid growth.
The potted trees have been inspected during the whole production process. Sample trees are randomly selected from each group to inspect the root development from the stem to the outer extremity of the root ball.
The cuttings were “potted on” from the tubes into 200mm pots in March 2008. The cuttings roughly doubled in size from May and showed a more upright ‘tree like’ form.
The trees were staked through the first four potting stages to provide stability until a firm woody stem was established. At each potting stage the root ball was shaved to make sure any circling roots from the previous pot were removed. This is very important as it ensures all roots are directed out into the new growing medium and can ultimately ensure a radially even root structure. A good root system gives all trees the greatest chance of establishing into healthy, stable mature trees.
The trees have been “potted up” during the growing process at the following sizes:
Timing |
Tree Height |
Container Size |
|---|---|---|
May 2008 |
30 cm tall |
200mm |
December 2008 |
90 cm tall |
25 litre |
October 2009 |
1.5 metres tall |
500mm |
March 2010 |
2.5 metres tall |
200 litre |
March 2011 |
3.5 metres tall |
400 litre |
March 2012 |
5.0 metres tall |
600 litre |
At each potting stage the sides and bottom of the root balls have been shaved to produce good root development and remove any circling roots. This is crucial to ensure that all roots are directed out into the new soil to establish an even root structure.
The trees have been inspected at quarterly intervals during the entire growing process.
2012
The most recent inspection was conducted on 19th March 2012, when the trees were being potted from 400 litre bags up to 600 litre bags. Five trees from each batch were randomly selected. The potting mix was removed and roots growing from the tree trunk to the edge of the root ball were inspected.
The inspections confirmed that the trees are continuing to thrive. They have good structure above and below ground and there is no evidence of disease or pest attack that could affect their long-term health.
The trees now average 5.0 metres in height. Their canopies will be gradually “lifted” to produce a clear trunk height of 2.5 metres when planted. The next potting into 800 litre bags is proposed for Feb/March 2013.
Photographs of the Growing Process of the New Hill’s Figs
24: Karignan - 600 litre bags
Karignan Nursery (Central Coast NSW) trees in March 2012. Trees average 5 metres and have just been potted into 600 litre bags.
25: Karignan - newly pruned 400 litre tree
Karignan March 2012 - Recently pruned rootball of 400 litre tree at Karignan prior to potting into 600 litre bag.
26: Karignan - potting up process
Karignan March 2012 - Potting into 600 litre bag at Karignan.
27: Bangalow Nursery March 2012 - Trees in 400 litre bags prior to potting up
Bangalow Nursery March 2012 - Trees in 400 litre bags prior to potting up to 600 litre bags.
28: 400 litre tree after root pruning
Bangalow March 2012 - 400 litre tree after root pruning with only fibrous roots remaining at the edge of the root ball. The small ropy roots are cut away from the outside of the root ball prior to re-potting into larger container.
29: Bangalow – Checking branch unions
Bangalow – Selecting structural branches and checking branch unions.
Last Updated: Monday 16 April, 2012
