A tree expert has warned people not to stand or walk under trees in the coming week, saying some may have been damaged by Super Typhoon Ragasa despite not falling down.

Chiu Siu-wai, a retired professor from Chinese University’s school of life sciences, said even small gusts of wind or minor vibrations could cause such trees to collapse.

Hundreds of trees across the city were brought down by the storm, including some very old ones.

Chiu said many trees in Hong Kong grow too large for the limited underground space available, leaving their root systems unable to anchor firmly.

"The first week after a typhoon is most dangerous because these branches or even the trunk or the tilted trees... they might only need a small wind or a small vibration then it will fall. So to keep yourself safe, don't stand under a tree or walk under a tree because this is the most serious situation - suddenly you might find a branch fall onto you," she said.

Chiu added that the government should prune trees before they grow too large, as without space for their roots to expand, they pose a greater fall hazard as they grow taller.