As Island Landmarks, the nonprofit that owns the Mukai Farm and Garden, finished a weeklong open house at the historic site last week, the organization was dealt another blow by its critics.

The Washington Trust for Historic Preservation has added the farmhouse to its list of the most endangered historic properties in the state. The site was nominated for the list by the nonprofit Friends of Mukai, a group of islanders who say they’re concerned about the state of the historic farmhouse and Japanese gardens and would like to see them protected and restored.

The Washington Trust, the state’s only nonprofit historic perservation organization, will announce the farmhouse’s listing, along with a half-dozen other additions to its Most Endangered Historic Properties List, tonight at its annual conference in Vancouver, Wash.

“This is validation that the property needs attention,” said Lynn Greiner, a Friends of Mukai board member. “We just think the more visibility this gets, the more people will appreciate that our effort to save it is appropriate.”

However, the head of Island Landmarks, Mary Matthews, expressed surprise and disappointment at the listing, which she learned of last week.

“I don’t think the Mukai Farm and Garden is threatened,” Matthews said, standing outside the farmhouse on Saturday, the last day of Island Landmarks’ open house.

During the eight-day open house, Matthews and Nelson Happy, Matthews’ husband and an Island Landmarks board member, welcomed more than 80 people to the property just outside town on 107th Avenue.

Matthews said that although the house itself wasn’t open, she gave some visitors tours of the property and others showed themselves around and looked at the approximately 15 historical photos placed around the site that showed the property as it looked in the 1920s and 30s, when a large strawberry farm and fruit barreling plant were operated there.

“People were really nice and very interested,” she said.

On Thursday, when Matthews and Happy learned that the farmhouse would be added to the Washington Trust’s list of endangered properties, they quickly took action. They each drafted letters to the organization, arguing that the farmhouse was not endangered or at risk because Island Landmarks has been a good steward of the site, maintaining it, opening it to the public periodically and by appointment and working to find a qualified organization that could take it on and eventually restore the house and gardens.

“No one knows as much about this wonderful site, or cares for its preservation, as I do,” Matthews wrote in her letter. “I hope that you and your organization will perhaps think more charitably on our efforts now that you know the facts.”

Chris Moore, field director for the Washington Trust, said he presented the organization’s board with Island Landmarks’ request to reconsider the listing, but the board decided to keep the site on the list.

“It’s clear that there is uncertainty about the future of the resource,” Moore said in an interview. “That has kind of come front and center above all else.”

For years, the historic farmhouse and garden, purchased more than a decade ago by Island Landmarks, has been at the center of a heated dispute, with critics saying, among other things, that the property has fallen into disrepair and hasn’t been accessible to the public.

Last fall, a group of concerned islanders who would later form the Friends of Mukai attempted to wrest control of Island Landmarks by following the organization’s own bylaws to oust Matthews and other board members and install their own elected board. However, a judge ruled in November that the takeover was not done legally, a decision the group is now appealing.

And earlier this year, Allyson Brooks, a top official from the state Department of Archeology and Historic Preservation, voiced concern about the status of the house and what she called Island Landmarks’ apparent failure to live up to the terms of a state grant that helped purchase it.

“The State of Washington is considering its legal options to prevent further personal use of the property and further deterioration of the historic character,” Brooks wrote in a letter to Island Landmarks.

Matthews and Happy, however, insist they’ve been misrepresented and that they’re doing all they can, including loaning their own money to Island Landmarks, to maintain the property and keep it accessible to the public until a large, tax-supported agency can take it on.

“That’s what we have always wanted, and we have worked toward that,” Matthews said. “It’s difficult for people to understand that.”

Moore said the Washington Trust didn’t intend to take sides in adding the farmhouse to its endangered list, but to bring more statewide awareness to a turbulent situation around the house and what he called the property’s uncertain future. The trust, he said, would like to see Mukai have a clear stewardship plan in place, as well as a group that has the resources to provide longterm stewardship. He said the trust was willing to work with any of the stakeholders involved to see that happen.

“It’s not so much to say from our standpoint that somewhere along the line people are in the wrong, but that we have a situation right now that’s unfortunate, and we want to see it move forward,” Moore said.

In light of this week’s listing, the Friends of Mukai are organizing a June 1 event that they hope will draw even more attention to the property. The event, which the group is calling This Place Matters, will take place on the road outside the farmhouse at 1 p.m. and will include speakers, music and a group photo of all who attend. The event is co-sponsored by the Washington Trust for Historic Preservation, King County 4Culture and the Vashon-Maury Island Heritage Association. Rep. Joe Fitzgibbon Sen. Sharon Nelson and King County Executive Dow Constantine have all been invited to attend.

“The ultimate goal is to get the property revitalized,” Greiner said. “Friends of Mukai has a number of strategies to accomplish that, and this is just one. … We hope it will be a fun event but at the same time about a topic that we take seriously.”

Matthews, meanwhile, called the endangered listing upsetting but said she would continue to move forward on plans to maintain the property until an adequate agency could take it on. She’s also planning an open house for the second weekend in June, when the house will be opened for tours and information on the site’s history will be on display from noon to 6 p.m. June 7, 8 and 9.

“We keep saying this certainly isn’t for us, it’s for the people,” she said.