As the Leisure and Cultural Services Department announced yesterday that more than 20 trees posing a risk to the public needed to be cut down in the coming week, a fourth car in four days was hit by a falling tree. A 15-metre horsetail tree fell across Kadoorie Avenue, Mong Kok, in the morning, hitting a passing private car. The windscreen was smashed, but the driver was not hurt. The department said about 31 trees, mostly in parks, had been identified for removal because they were a hazard. Eight had already been cut down and the rest would be removed in the coming week. About a third of the trees were on roads in Yuen Long, Tai Po and Southern District. It said it had inspected the horsetail tree in April and found no problem. It blamed wet and windy weather for its collapse. Last Saturday, a car in San Po Kong was hit by a falling tree. On Monday, a 14-metre flame of the forest in Perth Street, Kowloon City, fell onto a taxi in which a driver was asleep. Also that day, a tree fell on an empty taxi in Tai Po Road. A tree collapsed in Stanley last year, killing a woman, prompting Chief Secretary Henry Tang Ying-yen to become the city's tree tsar. Ken So Kwok-yin, a tree expert with the Conservancy Association, said he found decayed roots that could have contributed to yesterday's accident. 'The department should find out the real cause of trees falling ... instead of just blaming the weather,' he said. Mr So said an increasing number of trees in urban areas have shown signs of ageing, and it would be wise for the department to focus its limited resources on high-risk trees that require better care and monitoring. University of Hong Kong tree expert Jim Chi-yung said large tree species might not be suitable for congested roadsides where little room was available for them to grow. Gary Cheung Siu-wing, head of the Hong Kong Leisure Services Staff General Union, said a serious staff shortage had made it impossible to inspect the city's 1 million trees. In a statement issued last night, the department said its officers and a pest controller inspected 70 trees in the vicinity of Perth Street, Dunbar Road and Shek Ku Street in Kowloon City yesterday and found no termite infestations. It had also hired a contractor to help assess trees as the typhoon season approached.