University of Hawai‘i at Manoa
UH Seal The founding college of the University of Hawai‘i, established 1907 Site Search | Directory
Skip BreadcrumbHome >> Our College >> Impact Stories >> Story

Branches of Control

By Office of Communication Services    Published on 12/23/2014 More stories >>

The skeletal outlines of dying albezia in this Puna forest are testament
to Dr. Leary’s herbicide technique and the dedicated work of the Big Island
Invasive Species crews.

The skeletal outlines of dying albezia in this Puna forest are testament to Dr. Leary’s herbicide technique and the dedicated work of the Big Island Invasive Species crews.

Everyone remembers the toll albizia trees took on Puna during last summer’s Hurricane Iselle, when they knocked down power lines, blocked roads, and crushed roofs and cars. Homeowners, natural resource managers, and others are now eyeing the albizias still standing, with an eye to bringing them down…less catastrophically.

The college’s research and extension faculty have been sounding the warning about these towering trees for more than a decade. Albizia (Falcataria moluccana, formerly Paraserianthes falcataria or Albizia falcataria) is not only huge and extremely fast growing; it’s very brittle, meaning branches and trunks can break without warning. It crowds out and kills off native species, competing for sunlight, water, and nutrients. And it changes the chemistry of its soil, making it more inviting for other invasives, including the rapacious strawberry guava.

One element of control of invasive plants, says CTAHR forester J. B. Friday, who advises landowners and community groups, is not to plant problematic trees in the first place. “First determine what you want from the trees you’re planting,” he explains, “and then find non-invasive alternatives that provide the same benefits.” Albizias have been used as ornamentals, for reforestation, and as nitrogen-fixers to fertilize soils. Some good alternatives include monkeypod (Samanea saman), narra (Pterocarpus indicus), and madre de cacao (Gliricidia sepium). Plant Pono, a project with which many CTAHR faculty, staff, and alumni are associated, provides more alternatives.

Dr. Leary (far right)
with members of the Big Island Invasive Species team.

Dr. Leary (far right) with members of the Big Island Invasive Species team.

Invasive plant specialist James Leary deals with the many albizias already growing. They can be expensive and time-consuming to eradicate, but Dr. Leary has pioneered a revolutionary technique for delivering mili-doses of herbicide directly to the trees’ vascular system that costs as little as $2 per tree and obviates the need for large amounts of chemicals. The dead trees that remain standing are much less of a threat: A recent article in Landscape Hawaii magazine reported that while the canopies of live trees acted as sails, causing hurricane winds to blow them down, the defoliated dead trees remained upright and did no damage. As importantly, dead trees do not produce new seed.

Dr. Leary comments, “The recent catastrophe of Hurricane Iselle reminded us of the real hazards presented by albizia. If we are going to spend millions of dollars physically removing these imminent threats, out of necessity, we also need to implement more cost-effective prevention strategies, towards sustainability.”

Visit:www.plantpono.org