A willow tree which snapped in high winds at the Shotover Jet base in Queenstown on Tuesday may have been affected by root decay.
Three independent arborists said yesterday based on photographs they had seen, it appeared the tree roots had been compromised, possibly as a result of root plate disturbance, the result of digging or a change in ground levels around the base of the tree.
Consultant arborist Mark Roberts, of Dunedin, said while there were ways to internally test a tree's health and stability, they were expensive and not often used.
However, visual tree inspections gave a good indication of tree health and arising issues.
Changes in the trunk diameter, texture or bark, the colour and shape of leaves and leaf distribution ''suggest what the tree is doing internally''.
Mr Roberts said trees should be inspected by a qualified arborist after major weather events, or annually, with some exceptions.
''If a tree's healthy and actively growing and the soil around it and the site around it hasn't changed, then you could probably get away with several years without looking at them.
''But what tends to happen is people, as a general rule, don't look up.''