The inclusion of 398 trees growing on stone walls on a list of inspected trees released by the government may cause needless worry and lead to misunderstanding that they are dangerous, a tree expert says. There are 1,000 trees growing on stone walls in Hong Kong, according to Jim Chi-yung, a University of Hong Kong geography professor. Most are in Central and Western District and are in good condition, he said. 'Listing the stone-wall trees may cause unnecessary panic and the public might demand they are all felled ... it would be hazardous for conservation work,' Jim said. In fact, trees that grew on walls were usually strong and healthy, he said. Their seeds have a one-in-a-thousand chance of germinating, Jim estimates, after being eaten by birds and then deposited on a wall. And the chance of a sprouted seed growing into an adult tree is, again, one in a thousand, he says. 'The tree that survives is very strong,' he said, and its was rare for a tree growing on a wall to collapse because its roots were firmly entrenched. The size of trees growing on walls is also in proportion with their roots, which are well supported. He said trees growing on walls were less likely to be damaged by people as they were high above roads. Jim also noted that few of the trees which have fallen after typhoons grew on walls.