By Ken Sakamoto, Star-BulletinWendy Craven, left, and Liz Keller pull up some invasive
water lilies that are threatening Kawai Nui Marsh.
MAY Day, goes the song, is Lei Day in Hawaii, with flowers blooming everywhere. True, but we'd be better off if some of them were blooming someplace else. It's the problem of invasive aliens, little green guys who threaten to take over our gardens and forests. Invasion of
the habitat snatchersAlien plants threaten native species
Listen to Wendy Craven and Liz Keller, who are in charge of a display of invasive alien plants to be exhibited at the Honolulu Academy of Arts May 8 through 10. The exhibit is part of "Pacific Horizons: Hawaiian Hospitality," a major flower show being produced by the Garden Club of Honolulu.
An alien plant is defined as "one that is a non-native plant, introduced accidentally or intentionally, and has become naturalized (spread and established without human assistance."
Some of the plants were brought to Hawaii as a food source for people or animals, others were brought to beautify the landscape. They came to do good, but stayed to do evil, largely because they got out of control.
Certain grasses were introduced as cattle feed. It turned out that the cows didn't find them tasty, and the grass now runs wild across the slopes of South Kona. Miconia has deeply veined, large, dark green leaves with brilliant purple undersides, and someone thought it would be a glorious addition to a garden. It escaped the garden and is killing off native plants in Hawaii rain forests.
Accidental arrivals came here by ship or plane in nonsterile soil, in other plants or on clothing, or were transferred by wind or sea or birds. Hawaii now has more than 800 alien plant species and some of them have become pests.
What is a problem on one island may not be a problem on another, because it hasn't gotten there yet. Craven said gorse is a noxious weed on the Big Island that hasn't yet invaded Oahu.
Once a weed like gorse establishes itself, it is spread by birds, pigs, hunters, hikers, tire treads, construction equipment, extreme weather conditions and by careless people.
Kawai Nui Marsh in Kailua is being clogged by water lettuce and small lily pads that have been thrown into the water by discouraged water gardeners.
Inspired by beautiful water gardens at Ala Moana Center and the availability of water plants at most nurseries, enthusiastic gardeners tried this out at home. Well, water gardening isn't as easy as it looks.
So after a brief fling at water gardening, some of the gardeners quit, and dumped their plants into the marsh where they thought the plants would have a second chance. How right they were, Keller said. "The plants have thrived to the point where they are now clogging up the waterways. The marsh drains into the ocean, taking some of the excess plants along. They die in the salt water and create a terrible smell."
Not all aliens are so obvious. Some are growing quietly in remote areas, destroying native plants. "Native plants, those that arrived here without human help, grow in small specialized habitats," Keller said. "These habitats are easily disturbed by the more aggressive, fast-growing alien plants."
In places where the aliens come from, they have natural enemies in birds, animals or insects that feed on them, but the enemies don't live here. Or else they come from areas with severe climates, particularly below-freezing weather, that keeps them under control.
Without predators or cold snaps to control growth, aliens spread quickly. They shade native plants from the sun, preventing reproduction. They dry up water sources, as they are threatening to do at Kawai Nui Marsh, and they alter the ecosystem. Certain native birds feed on only one or two varieties of native plants, and pollinate other native plants. When the first plants die, the birds die, and with no natural pollinator, the other variety dies.
So what do we do? "We do what we can," Craven said. They aren't asking you to go into the rain forest and pull up fire bush or kahili ginger. The ginger, a favorite ornamental, has a traveling root system and is choking out some native ferns.
"We want people to be aware of the problem and to be responsible," Keller said. "Don't bag volcanic cinders on your next visit to the volcano and bring them home. They can carry seeds or spores of invasive plants.
"Don't order wild flower kits or poppies or grasses from seed catalogs. They die off annually on the mainland, but here just go and on.
"Don't plant strawberry guavas or Christmas berries as ornamentals in your garden. They are both becoming invasive.
"When you pull out a weed or invasive plant, don't throw it on your compost pile. Either chop it up and burn it, or leave it in the sun to dry out and die so the seeds are no longer viable."
Finally, plant native plants whenever possible. They are acclimated and belong here.
The invasive plant exhibit is only part of the flower show. Visitors will see flower arrangements around such themes as "Boat Day" or "Poi Supper" or "Tutu's Cupboard," There will be prize-winning spathiphyllum, bromeliads, orchids and hibiscus.
A highlight will be the tropical rain forest created by Leland Miyano in the central courtyard of the academy, using huge ferns, vines, philodendron, monstera and orchids. None of these are invasive plants, except maybe to the staff of the academy.
Flower show
What: "Pacific Horizons: Hawaiian Hospitality," a flower show presented by the Garden Club of Honolulu
Gardening Calendar in Do It Electric!
Send queries along with name and phone number to:
Evergreen by Lois Taylor, Honolulu Star-Bulletin, P.O. Box 3080, Honolulu 96802.
Or send e-mail to features@starbulletin.com.
Please be sure to include a phone number.
Evergreen by Lois Taylor is a regular Friday feature of the
Honolulu Star-Bulletin. © 1996 All rights reserved.
