Albizzia, Friend or Foe
By Glenn I. Teves, UH CTAHR County Extension Agent
The first introduction of plants to Hawaii started with the arrival of Polynesians, who brought important food and utility plants to their new home. I remember noted Hawaiian botanist Isabella Abbott calling kukui an invasive species because it displaced many natives in valleys and mountainsides.
Over the last 240 years, thousands of plant species were introduced to create new economic opportunities as a western capitalist system replaced an ancient self-sufficient system. Today, most of the vegetation found below 2,000 feet, with the exception of a few isolated coastal systems, is introduced. Many have become invasive due to their aggressive growth habits and ability to disperse seed rapidly, and a few examples include Eucalyptus, Miconia, Banyan, Christmas Berry, Lantana, Formosa Koa and African Tulip.
Albizzia (Falcataria molucanna) was introduced to Hawaii from the Indonesian lowlands in 1917 and quickly spread due to its amazing growth rate, probably the fastest on the planet. It’s also the most prolific nitrogen-fixing tree, dropping 30,000 pounds of leaf and litter per acre per year and producing 1200 pounds of elemental nitrogen of 3,000 pounds of urea fertilizer in the process. This plant also has the ability to take in 200 tons of carbon dioxide per care, the compound that contributes to global warming.
Albizzia can also be used as high quality mulch and compost, and also an animal feed since it has a high protein content of 25 to 27 percent. As biomass, Albizzia is presently being used to produce electricity on Kauai, and will supply 15 percent of Kauai’s power needs. Albizzia wood is light and soft, and is also used in the core of plywood in much of Southeast Asia since it’s considered equal to Ponderosa pine, a common wood used for 2x4s and framing wood.
However, any plant that cannot be managed and spreads rapidly is an invasive weed, and Albizzia fits these attributes due to its aggressive growth habit, growing at the rate of 15 feet per year and reaching over 100 feet in 10 years. The canopy of one tree can cover more than 150 feet in diameter. The closest plant we have to this is Ironwood, which can grow about 10 feet a year but doesn’t come close to Albizzia’s spreading canopy due to its conical growth habit.
An interesting growth habit is its propensity to shed limbs since branches break easily, and can create a dangerous situation when growing near residences. Due to its sheer size, with heights exceeding 200 feet and trunk diameters exceeding 10 feet, it’s very costly to control them and pruning or removal should only be performed by a professional arborist. In an empty house lot near Pahoa on the Big Island, the cost of removing Albizzia exceeded the value of the lot, so the lot owner decided to sell the lot. With a branch hanging over a neighbor’s house, this also became a potential liability.
Deciding what kinds of plant species to grow on your house lot or farm requires a determination of the benefits and costs of the species selected, and also its invasive characteristics. If it costs too much to manage and control them, it may be prudent not to plant them at all.