It may cost thousands of dollars in lost revenue, but a small band of O'ahu nursery owners has become the first group to sign a pact against selling imported plants that can overrun native ones in the Islands.

The members of the O'ahu Nursery Growers Association believed that their decision in October was as much to protect their business interests as well as Hawai'i's environment.

"We love plants more than anybody in Hawai'i. It's been my whole life," said Bill Durston, the owner of Leilani Nursery in Waimanalo. "We want to help out — and keep in business. The nursery industry has to lead the way, not be led. We're trying to take care of Hawai'i while getting ahead of (potential) regulations."

Among other things, the eight companies agreed to stop selling seven of the more popular and problematic plants — the Australian tree fern, rubbervine, smokebush, butterfly bush, pampas grass, mule's foot fern and glorybush.

The voluntary ban comes with a price: At Durston's Leilani Nursery, the Australian tree fern alone accounts for about $42,000 worth of his annual sales.

"Eliminating the Australian tree fern, especially, is a sacrifice for them," said Carter Smith, weed risk assessment liaison with the state Department of Land and Natural Resources' Kaulunani Urban Forestry Program. "That's a very significant step on their part."

But Christy Martin, spokeswoman for the state Coordinating Group on Alien Pest Species, said, "a lot of people want to do what's right and what's good for the environment. We hope it doesn't cost them too much because many of us started out running small businesses."

Last year, Martin approached Durston with the idea of getting the O'ahu Nursery Growers Association to adopt a voluntary code of conduct similar to the one that came out of a 2001 workshop at the Missouri Botanical Garden.

While each island has various nursery, growers and landscapers associations, Martin focused first on Durston and his membership with the O'ahu Nursery Growers Association.

"The ONGA group has always been very open to these sorts of ideas about protecting Hawai'i," she said. "And Bill is an important person in the industry. He supplies Costco, Home Depot ... His nursery products are everywhere. I thought, 'Let's get a very well respected and organized group on board and see where we can go from there.' "

It took little effort to get each member to sign the agreement.

"We're a pretty close-knit group and we understood what is going on," said Richard Nii of R&S Nii Nursery in Hawai'i Kai, who is the president of the O'ahu Nursery Growers Association. "We understand, as nursery people, that our job is to sell plants. But we have to be careful that the seeds don't germinate all over the place and create a big problem."

Like the other members, Nii has since begun phasing out his inventory of the newly banned plants. Instead, he will encourage customers to buy different varieties that look just as nice but won't spread and harm Hawai'i's fragile environment.

Eventually, Nii hopes to replace any lost revenue with new sales of different plants.

And that's the point that Martin hopes other groups see as they might consider adopting similar codes of conduct.

"The Australian tree fern is one of the biggest sellers because people like that tropical look, but they don't realize the spores blow into the wind and are definitely spreading into the forest," Martin said. "If it costs the same for an Australian tree fern or a giant 'ape (giant dryland taro), I have faith in people to take care of the environment."

Nii has heard different thoughts on whether other groups will follow the example of the O'ahu Nursery Growers Association.

It is, after all, a voluntary pact.

"We can't twist their arms," Nii said. "We can only hope."

Reach Dan Nakaso at dnakaso@honoluluadvertiser.com.