SINGAPORE: The heritage Tembusu tree that fell at the Singapore Botanic Gardens on Saturday (Feb 11), killing one person and injuring four others, was last inspected and found to be healthy in September last year, according to the National Parks Board (NParks).
The 40m-tall tree was uprooted at the edge of Palm Valley in the Botanic Gardens, bringing down surrounding palm trees as it fell. The tree was more than 270 years old and predated the establishment of the Gardens, according to NParks.
NParks added that as a Singapore Botanic Gardens heritage tree, the tree was inspected twice a year - more frequently than other trees in the Gardens.
"The tree was also protected by a lightning conductor and fenced off to prevent compaction of its root zone by visitors. Leaf litter was routinely applied to the root zone to encourage healthy root growth," it said.
Lead arborist Ng Tze Peng at TP Arbo Care said a combination of factors - the environment, climate and the tree's condition - could have caused the tree to fall.
“Tembusu is commonly known for its hard and solid wood tissue due to its slow growing nature,” said Mr Ng. “Age does not mean that the tree would weaken structurally - it could weaken due to wound or decay inflicted on the tree along its course of growth.
“In order to determine the cause of the incident, (the authorities) would have to study the structural condition of the overall tree, especially its root system, the environmental and climatic condition at the time of the incident,” he added.
Tan Huan Arboriculture Services managing director Andy Tan said he would expect a tree this old to have been inspected every month, to ensure that issues such as fungi and termites did not set in.
Nonetheless, he said it was unlikely that fungi or termites were the cause of the incident. These issues could take up to one or two years to weaken such a big tree enough for it to fall, and tell-tale signs such as unhealthy leaves or termite tracks would be evident months before, according to Mr Tan.
The tree expert's opinion was that the most likely cause of the tree toppling was water-logging due to recent heavy rains. This could result in the surrounding soil loosening and the roots rotting. Strong winds during storms could have further exacerbated the problem, he added.
"Still, you would seldom see this for the Tembusu tree as they have very large roots ... their base is very strong."
NParks is investigating the cause of the tree falling.