Hyde Park - New Hills Figs for Central Avenue
To ensure that the magnificent Central Avenue in Hyde Park is preserved for future generations, new Hills Figs are being grown to eventually replace the original trees.
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 diseased and are 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 2012.
A tree supply contract to grow the replacement trees was tendered and awarded in late 2007 to Trees Impact Nurseries. 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.
The trees will be grown in two separate locations to minimise the risk of loss from disease, storm or fire.
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 are taken from the non-woody branch tips, cut to size, stripped of leaves from the lower section and planted into a growing medium. The purpose at this stage is for the cuttings to establish a root system. The process of collection and planting must be completed quickly using the utmost standards of hygiene. 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 will be 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 will be staked through the next few potting stages to provide stability until a firm woody stem has established. At each potting stage the root ball is shaved to make sure any circling roots from the previous pot are 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 most recent inspection was conducted on 9 December 2008 while the trees were being potted from 200mm pots up to 25 litre bags. Four (4) out of 100 trees were randomly selected and the potting mix removed from the root balls to permit inspection of the root development from the stem to the outer extremity of the root ball.
The trees were healthy and free from suckering, with the root crowns at the surface of the root ball. There was no evidence of disease or pest attack that could affect the long-term health of the trees. The roots were found to be in a healthy condition with fine fibrous roots extending outwards and downwards to the outer edges of the root ball. The sides and bottom of the root balls were shaved during the potting process to reduce elongated lateral growth and limit the possibility of root girdling.
The stems were taped to their stakes and every second lateral branch pruned to stimulate upright growth. The trees are being grown to produce a clear stem height of 2.5 metres when delivered for planting.
The next “potting on” stage is scheduled for Spring 2009 when the trees will be potted into 500mm bags.
Photographs of the Growing Process of the New Hill’s Figs
1: Taking Cuttings from the Selected Parent Tees
On 15 January 2008 foliage cuttings were taken from two separate Ficus microcarpa var Hillii (Hills Weeping Fig) located opposite the Sydney Art Gallery. Note the trees major branching structure is free of branch inclusions. Branch inclusions are an inherent genetic weakness, in some tree species, which are prone to failure.
Ficus microcarpa var Hillii (Hills Weeping Fig) - Sydney Art Gallery
2: Cuttings Prepared for Transport
The small cuttings were placed into ‘esky’s’ to remain cool while be transported to the nursery.
Cuttings Prepared for Transport
3: Cuttings in the Tube Stage (March2008)
At this stage the foliage cuttings have been cut to size, the lower stem cleared of leaves and then planted in soil filled ‘tubes’. The initial aim is for the cuttings to develop their own root systems.
Cuttings in Tube Stage 200mm pots (March 2008)
4: Cuttings being Potted up from the Tubes into 200mm pots (May 2008)
The cuttings have now doubled in size and have taken on a more upright, tree like form. The new root system is clearly visible at the base of the cutting.
Cuttings being Potted from the Tubes into 200mm pots (May 2008)
5: Trees ready for Potting on to 25litre bags (December 2008)
A view showing root establishment right through the growing medium in the 200mm pot. The edge of this soil will be trimmed off prior to potting on, to halt any root girdling.
Trees ready for Potting on to 25litre bags (December 2008)
6: The trees Potted into the 25 litre bag (December 2008)
Minor formative pruning was carried out at the time of potting on to reduce elongated lateral growth and encourage a tall, straight tree with a single leader.
Trees Potted into the 25 litre bag (December 2008)
7: The Hyde Park Hill’s Figs in 25 litre bags (February 2009)
The trees are growing well and the roots have now “locked up” the soil in their containers. The 25 litre trees are scheduled to be potted on to 500mm bags in September 2009.
Hyde Park Hill’s Figs in 25 litre bags (February 2009)
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Last Updated: Wednesday 29 April, 2009
