Royal palm trees are a thing of beauty, but a University of Miami botanist said Wednesday the stately trees being planted along a busy Miami area highway are also dangerous and threaten motorists.

Julia Morton, an economic botanist for the University of Miami who studies man's use of plants, said the fronds from the city's 248 royal palms being planted along a 2-mile stretch of South Dixie Highway are unmanageable and dangerous.She said the fronds that dehydrate and fall from a 20-foot tree weigh about 30 pounds.

"Every month, one new leaf protrudes from the top of a palm and concurrently one old leaf turns brown and falls off," she said.

City Attorney Robert Zahner said the city would probably have to pay if someone was injured or there was property damage from a falling frond. But he said the trees' beauty outweighs potential liability.

"We have some 27,000 trees," Public Service Director Mike Barger said. "It's our intention to monitor the palms."