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Branching Out Treescape travels to save Singapore Fig

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Singaporean Government agency, Sentosa Leisure Group, engaged Treescape to perform tree remediation works on a large Johor Fig. The tree was planted 140 years earlier by British soldiers stationed at the island’s military fortifications, and is heritage listed.

In August 2011, Treescape prepared a tree assessment for Sentosa, outlining tree health, risks and possible remediation options. The report concluded that the tree was in serious decline. In particular, its roots were drowning due to an increased water table that had resulted when a neighbouring pond was upgraded two years earlier.

In July 2012, Daniel Oaten and Anastasia Browne, of Treescape, travelled to Singapore to implement the recommendations of the tree assessment report.

After a visual inspection, the team established that the tree’s health and vigour had drastically declined since the time of the initial assessment. The decline was evident in the degree of canopy dieback, borer infestation, chlorotic leaves and extensive decay. In addition, the tree had started to prolapse as the water saturated soil struggled to support its weight.

To allow the tree to slowly adjust to the proposed modifications to its condition, remediation works were broken up into two stages.  To deliver the work, Treescape formed alliances with two Singaporean landscaping companies, who were charged with undertaking the maintenance and rectification works over 12 months.

Stage one of the projects was completed in July 2012. It included installation of a root/moisture barrier to separate the neighbouring pond from the tree’s roots. This worked by acting as a dam at 1.5 metres deep.

The tree also underwent spraying for, and manual removal of, borer and decay. The canopy foliage was sprayed to reduce insect infestation.

A ‘Cobra’ cabling system was installed to support the tree’s south-eastern structural limb, where all structural and aerial roots had been removed. Measurement and design of support legs was also completed, and the soil was injected with microbiologically active soil fertiliser, soil inoculums and bio fertilisers.

Stage two was undertaken during August and September of 2012. It involved the installation of a bore pump to ensure the tree’s root zone would not retain the water that it shed. Support frames were also constructed and installed, with suspended planting added to hide the support frames.

Elevating drain walls were implemented around the tree to minimise overflow, and compost tea brewing and soil injections encouraged symbiotic fungi establishment.

At this stage, an extensive Plant Health Care Programme began. The Programme will recondition the soil and replace lost nutrients. Vertical coring and soil decompaction works will enable oxygen and nutrients to enter the hard clay. Cured forest mulch will be spread around the drip zone.

To maximise the tree’s recuperation, soil condition reports will be sent to Treescape weekly. Treescape will then devise prescriptions required for the following month.

 
 

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