Whack! Slice! Whap! The stalks of Kahili ginger fell to the ground. My older brothers and I moved on to a new patch. They had their machetes; I, being the youngest, was armed with a stick. We were on a mission to destroy the invader!
Example of dense Kahili ginger (H. gardnerianum) growing near one of the plots
Ever since I can remember, Kahili ginger ( Hedychium gardnerianum) has been an enemy of my household. It dominates the ground cover and blocks out sunlight, preventing the regeneration of native plants, and it's difficult to kill. Having huge rhizomes makes the ginger incredibly hard to pull out by hand; a shovel is required to drive the plant out of the ground. Even then, there are always some bits of the rhizomes left behind, which makes the ginger practically impossible to entirely remove. Many of the park rangers at Hawaii Volcanoes National Park (HAVO) grimace when they hear "Kahili ginger." The park has even asked the artists who sell their work in a small gallery in HAVO not to depict Kahili ginger in their artwork. HAVO also tries to keep the ginger away from endemic, and sometimes endangered, plants, usually by digging out the rhizomes by hand, with the assistance of a pickax, or a couple of machetes and a shovel. I grew up assuming that I was doing a very good deed for the environment by depleting the ginger population. I never once wondered, Is ginger truly bad for the environment? Does it really affect native germinants? I never once pondered the question of whether Kahili ginger changes the soil; maybe it actually helps native plants and lives in perfect harmony with them. Now I know.
Through a summer conservation program with HAVO, I grew to ponder this question more and more. Not only for Kahili ginger but for other invasive plants as well, such as Morella faya, or Falcateria moluccana, which have both been part of previous studies. I decided that Kahili ginger was what I needed to study. To do this, I made a detailed procedure in order to collect the data required so I could analyze the problem.
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Detail of Plot 3 drawing
First, I made four four-meter-by- four-meter plots, then divided each plot into four two-meter-by-two-meter quadrats labeled A, B, C, and D. The plots were labeled 1, 2, 3, and 4. Quadrats labeled A were those in which the ginger was dug out, and quadrats labeled D were those in which ginger was cut out at ground level. Quadrats B and C were controls, and nothing was done to alter them. Each plot was then mapped out on graph paper, with quick sketches of some of the plants in each. (Click to view enlarged drawings: Plot 1, Plot 2, Plot 3, Plot 4)
A healthy Kawa'u (Ilex anomala) in Plot 4C
Photos of dug out plots (Click to enlarge)
About four native plants in each quadrat were measured for height, from ground level. Some of the native plants whose heights I measured were 'ie'ie (Freycinetea arborea), pa'iniu (Astelia menziezii), kawa'u (Ilex anomala), and pilo (Coprosma ochracea). These four graph papers were used as my data charts. In each quadrat, I took four pH measurements in the soil. That's 16 per plot, or 64 total measurements. The rod of the pH meter was stuck into the ground and left in until the meter showed a definite number, which usually took about 30 seconds. The measurements were recorded on notepaper, and the position of the measurements in the plots was recorded on the data charts. In all quadrats A, the ginger was dug out. In all quadrats D, the ginger was cut as close to ground level as possible, so that less than six centimeters, or just the stalk, was left protruding out of the ground.
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