LIHU'E, Kaua'i — Conservation organizations statewide are fighting to slow an invasion of alien plants that are spreading from home and commercial landscapes into the Hawaiian native forest.

A notable invader, the Australian tree fern, is favored for its fast growth, dense canopy and tolerance of a range of growing conditions. But its tiny spores readily spread on the winds and are supplanting native species in forests around the state.

Although many of the state's nurseries have agreed to halt sales, it's still available at a number of major retailers.

"You can still find it in lots of the larger stores. It's about the dollar," said Joylynn Paman, spokeswoman for the Maui Invasive Species Committee, who said landscapers on her island are working on a program to stop using the worst invasive plants.

If some outlets continue to sell the invasive species, it reduces the effectiveness of the entire program, said Jacqueline Kozak, of the Kaua'i Invasive Species Committee.

"It's unfair to the smaller nurseries that are taking an economic hit and ecologically ineffective," Kozak said. "It needs to be an across-the-board commitment."

Some stores are still learning about the issue. Among the big-box stores still selling some invasive species are Wal-Mart and Home Depot. But both, in response to calls from The Advertiser, said they had been unaware of the issue and are reviewing their plant sales programs.

"Being good stewards of the environment is very important to Wal-Mart and our associates. Because of that we are reviewing the plants we currently offer our customers in Hawai'i and will provide an update to the communities we serve in the near future," said Wal-Mart spokeswoman Karen Burk.

Home Depot spokeswoman Kathryn Gallagher said the issue is new to the company, but "we're going to work with the appropriate agencies, and we'll tailor our business to meet the needs of the location."

YOU CAN SEE EFFECTS

The impact of the aggressive alien species is clear in Hawai'i's forests, said Kaua'i craft maker Linda Hunt, of Wailua Homesteads.

"When we go up into the forest to pick maile and mokihana, there's a lot of invasive plants. People go up to pull them out and herbicide them, but there's not enough volunteers to make a dent," Hunt said.

The Kaua'i Landscaping Industry Council in June joined the O'ahu Nursery Growers Association in signing on to a program of the Missouri Botanical Garden and The Nature Conservancy — a code of conduct to help prevent the spread of invasive species. In the code, growers agree to work with experts to identify potentially invasive plants, develop alternatives to the use of those plants, phase out the sale of the invasive species, and encourage their customers not to use them.

Richard Beach, operator of Alexander's Nursery on Kaua'i, is not a member of industry groups, but completely supports the goal.

"We've destroyed all our own Australian tree ferns, and we're now destroying them in our clients' places," Beach said. "It is one of the most scurrilous invasive species. When you see a road cut left bare, they appear. I've found them coming up in clients' yards."

His argument to customers who mention using invasive plants in landscaping is simple.

"There is a serious movement to preserve what we can of Hawai'i's forests. The tradeoff is that you help play a part in preserving the 'Hawaiianness' of Hawai'i."

The Kaua'i Landscaping Industry Council has agreed to stop the sale of a dozen plants: Australian tree fern, rubbervine, smokebush, butterfly bush, pampas grass, hiptage, fountain grass, glorybush, fiddlewood, kahili ginger, common St. John's wort and Indian rhododendron. Earlier, O'ahu nurseries agreed to stop selling 10 species, many of them the same as the Kaua'i ones.

PROBLEMS EVERYWHERE

Different weedy species are bigger problems in specific environments. The Nature Conservancy conducted aerial surveys of the Kaua'i forests, and "I've never seen a weed species that can spread as far and multiply and grow as fast as an Australian tree fern here on Kaua'i," said the conservancy's Trae Menard in a prepared statement.

Kaua'i Nursery owner Lelan Nishek, president of the Kaua'i council and vice president of the Landscaping Industry Council for Hawai'i, said he destroyed $8,000 worth of Australian tree ferns and has launched an extensive program to propagate the native hapu'u tree fern instead.

"I even cut down the Australian tree ferns in my own yard" after seeing how invasive they were in the natural environment, he said.

Christy Martin, director of the Coordinating Group on Alien Pest Species, said pampas grass is a particular problem on Maui, after it became a popular landscaping plant in Kula.

"We're finding it in Haleakala Crater — even in the back of the crater where nobody goes," she said.

In southeast Moloka'i, the rubbervine is spreading. Fountaingrass forms clumps across much of the Big Island's lava fields, Martin said.

Miconia and ivy gourd continue to be severe pest problems in many parts of the state, but they're not listed among the nursery problem plants because almost all nurseries now understand their risk and won't market them, she said.

WORKING ON EDUCATION

Landscape professionals can learn about the invasive potential of new plants they're considering with a program called the Weed Risk Assessment. For many known plants in Hawai'i, the assessments have already been done.

"If you bring things in from other parts of the world, please get them screened before you plant them and sell them," Martin said she tells people who import new plants.

Her group and the invasive species committees in the four counties are working to expand industry and public knowledge about the threats of invasive plants.

"If there are people working hard in the upper forests to stop invasive species, it is important for the community to see that the nurseries aren't selling the very same species down below," Kozak said. "It shows that we are all working together."

Crafter Hunt said that many people insist on showy non-Hawaiian foliage because they don't recognize the value of native plants.

"There's so many invasive plants, and people keep bringing them in. They don't see the natural beauty of our plants, our ferns," Hunt said.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.