Monday, August 11, 2014

ALBIZIA – Beautiful Tree Or A True Menace?

 Hawaii was recently hit by tropical storm Iselle. Many streets in some locales, especially an area called Puna, were strewn with uprooted trees and fallen branches. The following article is about those trees - ALBIZIA. These albizia trees that quickly spring up in vacant lots or recently cleared land have become one of the worst invasive species on the Big Island of Hawaii. It has been called  “the tree that ate Puna”.

This albizia tree, Falcataria moluccana, is also named Albizia falcate, A.moluccana and others), and is a native to such places as Papua New Guinea, the Bismark Archipelago, and the Solomon Islands. The wood is used for light weight construction, cabinets, furniture, toys, and match sticks.
It is a fast growing tree to over 100 ft. tall. The tree can reach heights of more than 20 feet in the first year and to 60 feet by the end of ten years. It is described as a deciduous tree with wide-spreading branches, capable of shading over half an acre.  The tree produces large seed pods 4-5 inches long and about ¾ inch wide. It grows from sea level to about 3,200 feet elevation.  It is a nitrogen fixer, meaning that with the help of some bacteria residing in its roots, it can pull nitrogen out of the air and convert it to a form that roots can absorb. Because of this ability, it is used in many countries to improve soils as well as provide shade in coffee plantations.
This may make it sound like a pretty decent tree. But Dr. J.B. Friday, Extension Forester with the University of Hawaii, states “In Hawaii this tree is invasive in native`ohi`a forests as well as on land disturbed by human activities (especially bulldozing). It causes the`ohi`a  to die off and makes it easier for other invasive species like strawberry guava, clidemia and possibly miconia to grow under it and further degrade the forest. It also improves habitat for the tiny invasive coqui frog. These trees are a distinct threat to our native wet lowland forest ecosystems such as there are in Puna.”
Because of their brittle wood and weak structure, albizias are an even more serious problem to homeowners. Strong winds can cause large limbs to drop onto whatever may be underneath them, damaging homes, other structures and power lines. The fragile branches often cause traffic hazards by dropping branches on the highway.
A major problem, especially in Puna, is that people sometimes hire a bulldozer to clear their land. They clear the native ohia/uluhe forest, which is somewhat resistant to albizia invasion. If they are absentee landowners, they may not return for a few years and when they do return, an albizia forest has sprung up. Albizia is much bigger and faster growing than ohi`a, so the native trees cannot compete. To complicate matters, there is now a source of seedpods for the albizia to invade the neighbors' land. Dr. Friday advises not to clear the native forest on a lot unless you have another use planned for it. Otherwise albizia will come in and take over and you'll have a huge problem.

What to do: Leave the natural vegetation untouched—don’t bulldoze—until you are ready to utilize the land. Eliminate albizia seedlings and small trees before they become a problem.
Methods of control:  
After trees are cut down, immediately apply herbicide to cut stumps. Triclopyr amine is effective at concentrations of 7-10%.  For larger trees near buildings it may be advisable to first contact an arborist to determine the safest and most effective course of action to take in removing the tree.
The US Forestry Service in Hilo has an excellent publication entitled “Albizia – The Tree That Ate Puna” authored by C. Sumida, F. Hughes and Kathleen Friday.   For a copy write to USDA Forest Service, Institute of Pacific Islands Forestry at 60 Nowelo St, Hilo, HI 96720; or call at (808) 933-8121