Fast-growing, fragile trees are looming threat
By Colin M. Stewart
Tribune-Herald Staff WriterIt’s only a matter of time, says a group of Hawaiian Beaches residents, before someone is seriously injured, or worse.
"People are going to die soon," agreed University of Hawaii at Hilo associate professor of biology Becky Ostertag.
What has the Puna residents and experts so concerned is the albizia tree.
A relative newcomer to Hawaii, albizia were introduced here in 1917 by botanist Joseph Rock as an ornamental tree and for reforestation purposes.
With its tall white trunk and wide-spreading, umbrella-like canopy capable of shading up to a half acre, the albizia tree makes for a pleasing contrast to the black outcroppings of lava rock and scrubby underbrush so prevalent in the Puna area.
It is one of the fastest growing trees in the world, according to albizia expert Flint Hughes of the U.S. Forest Service.
The tree can grow to 20 feet tall in its first year, 45 feet in its third, and 60 feet by the end of its 10th year.
It is albizia’s ability to grow so quickly, however, that makes it a threat to those under its expansive network of branches, said Hughes.
"There’s a couple of things that make them a potential threat, particularly in Puna," he said. "One is that they grow very fast, and they get to be quite large."
Albizia form a symbiotic relationship with bacteria capable of pulling nitrogen from the ground to nurture the tree’s roots.
"They house the bacteria and feed the bacteria carbon, and in return the plants are able to obtain the nitrogen."
That has enabled albizia to outperform native plants in Puna.
"Because albizia has this association, it can grow on these very rocky substrates with very little soil and very little nitrogen, getting very tall and big very quickly, growing on this substrate that doesn’t support them," Hughes said.
Rather than sinking deep roots, the root systems tend to grow out horizontally when they encounter rock, making the trees unstable.
"That’s why it’s one of our biggest threats," he said.
The second reason albizia is a problem is that the wood is very light, making its structure weak. The light wood can’t support the mass of the fast-growing tree, and branches break off and fall.
Residents off of Kahakai Boulevard in the Hawaiian Beaches subdivision are no strangers to the threats posed by the albizia trees.
HELCO trucks regularly travel the neighborhood repairing power lines downed by toppling albizia trees, said resident and community leader Fred Blas, 59.
On April 16, he said, a large tree fell on North Puni Mauka Street, taking out power lines and fences in the front yards of his neighbors.
The 75- to 100-foot tree, which was cut into pieces that lie alongside the road, landed within four or five feet of the trampoline where Brenda Kaluna’s seven grandchildren play every day.
"If my grandkids were out there — good thing it wasn’t a Furlough Friday — they would have been hit," she said.
Her next-door neighbor, Dave Martin, 76, was mowing his lawn when the tree crashed through his white picket fence.
"I was trying to start my Toro, but it wouldn’t start. I felt the breeze of it when it fell," he said. "I would have been under it if the mower would have started."
Neighbors from five or six different households in Hawaiian Beaches spoke with the Tribune-Herald on Wednesday. They said they have always cut down albizia trees growing in their yards. But, they said, trees in their yards aren’t the problem. Many of the larger albizia trees grow on undeveloped lots.
The tree across from the Martin and Kaluna homes sat on a vacant lot owned by people who live off-island, Blas said.
"People need to know that it is their responsibility to cut these rubbish trees down before someone is hurt," he said.
"We’re concerned about how dangerous these trees are. We are concerned for our safety, and we want people to know that they need to control their growth."
Blas said he spoke with a county representative, and he said county employees are working to contact property owners with dangerous trees.
A call to the mayor’s office Wednesday afternoon seeking comment was not returned as of presstime.
People seeking more information or advice concerning albizia trees may contact Flint Hughes at (808) 933-8121, ext. 117.
E-mail Colin M. Stewart at cstewart@hawaiitribune-herald.com.
Managing albizias
What you can do:– Leave the natural vegetation untouched — don’t bulldoze — until you are ready to utilize the land. Albizia grows rapidly in bulldozed areas.
– Eliminate the albizia seedlings and small trees before they become a problem.
– Deal responsibly with "hazard trees." Trees that pose a hazard should be removed professionally.
Methods of control:
– For medium-sized to large trees, and any trees near structures, contact an arborist for free consultation to determine the safest and most effective course of action to remove the tree. An arborist will help you determine when professional removal is necessary.
– Fell saplings and young trees and apply herbicide to cut stumps immediately. Triclopyr amine is effective at concentrations of 7 to 10 percent. Before applying any pesticide, applicators must determine that the product under consideration is correct for the intended use site according to the label on the container or package.
Source: U.S. Department of Agriculture
