The towering old eucalyptus whose branch fell and killed a 4-year-old girl in a Highland Park schoolyard had not been pruned in recent memory and belonged to a species known for dropping large branches, tree experts and a school official said Monday.
A large branch from a nearby tree crashed to the ground about a month ago as a fifth-grade class looked on, according to a school official and a witness, but no one was injured.
As a result of the fatal accident at Buchanan Street School last week, the Los Angeles Unified School District has ordered an inspection and pruning program involving the estimated 750 eucalyptus trees throughout its school grounds, district legal adviser Ron Apperson said Monday.
Apperson acknowledged that the tree had last been pruned "a good time ago" and was scheduled for pruning in the next few months. However, he said it showed no signs of disease and denied that the tree was unsafe. "Such sudden limb drops are rare and difficult to predict," he said.
Several tree experts told The Times that it is difficult to predict which limbs will break. They said that the 80-foot-high ribbon gum variety that killed the preschool girl is one of several types of large, heavy eucalyptus trees prone to suddenly drop branches.
"That tree was dangerous," said John Sevier, who owns a San Diego firm called Tree Safety and frequently testifies in liability cases involving death or injury because of falling tree limbs. He examined the tree over the weekend and found evidence of the break in the other tree just a few yards away.
"We were just finishing PE and we saw it fall," said Sharah Salvador, 11, recalling the earlier incident.
She said her fifth-grade class, including the teacher, heard a loud crack across the playground and turned to see a limb crashing on the sidewalk just outside the playground. "It scared a few of us," she said.
Apperson confirmed that the other incident occurred, but said the breaks were the only ones at the school in years.
Carmen Munguia of Highland Park was killed Wednesday afternoon by a falling limb when she went to the school with her mother to pick up an older brother. It was a windless, sunny day, and witnesses said the branch cracked and fell for no apparent reason. The branch was about 35 feet long and 10 inches in diameter.
Such breakages are known to horticulturists as "sudden limb failure" or "summer branch drop." The causes are not fully understood.
Paradoxically, most such accidents happen on calm, sunny days in the seemingly safest of places--parks, playgrounds and golf courses--and the victims frequently are children, experts say. A 4-year-old girl was killed in 1983 when a eucalyptus branch just two inches thick fell on her at the entrance to the San Diego Zoo. A 10-year-old boy was killed at the Los Angeles County Arboretum in 1977 when a eucalyptus branch fell on him during a school field trip.
"For some reason, this often happens in hot, calm weather in the afternoon, or after such weather," said Richard Harris, a professor emeritus of landscape horticulture at UC Davis and one of the few acknowledged experts on the phenomenon.
"We believe it has something to do with moisture content. But we don't really understand it because the most common time for it to happen is in the afternoon when large branches can be many pounds lighter than in the morning, when they are filled with moisture."
Such accidents kill an average of one person a year in California and injure many more, according to Allison Berry, assistant professor of environmental agriculture at UC Davis, who is coordinating a three-year study of the problem.
More than 500 such limb failures have been recorded by certified arborists, or tree specialists, in California in the past three years, Berry said. At least a quarter of the incidents involve eucalyptus trees, partly because the trees are so common.
"But eucalyptus does seem to have a high incidence of branch failure in general," Berry said. "I must say, I always look up when I'm under a eucalyptus."
In Australia, Sevier said, some eucalyptus species are known as "widow makers."
While many of the hundreds of eucalyptus species in California are considered safe, some of the largest and most common are known for their limb breakage. Among them are the blue gum, red gum, sugar gum and ribbon gum.
The tree that killed the preschooler last week was probably planted about 40 years ago when horticulturists were less aware of its danger, according to Vance Tucker, a Cerritos tree expert who is a consultant to several local cities, golf courses and racecourses.
"Certain varieties (of eucalyptus) should never be planted in high-use areas," Tucker said. Asked if such trees should be planted in schoolyards, he said: "It's not something I would want to be responsible for."
Eucalyptus were imported from Australia in the mid-1800s to provide wood for railroad ties and trestles, and furniture for the growing population. But the wood warped, making it unusable. One of the largest and most common species, blue gum, was put into service making windbreaks in citrus groves. Many other varieties of eucalyptus are considered safe and well suited to California, experts said.
Careful maintenance over the life of a tree can reduce hazards, Tucker and others said. Poor pruning can create more hazards, they said. Inexperienced trimmers can mistakenly "hatrack" large eucalyptus, or cut the foliage so far back that the remaining trunk and limbs look like a hatrack. In such cases, experts warn, new foliage grows back so fast it is much weaker--and vastly more dangerous in most cases--than the old.
Times staff writer Andrea Ford contributed to this story