STOCKBRIDGE — Berkshire Botanical Garden, for nearly a century a seasonal venue featuring occasional winter events, plans to build a 5,000-square-foot glass conservatory that will allow it to become a fully four-season destination.

The plan, announced Saturday at the organization’s annual Fête des Fleurs garden party, is currently in the planning and design stages, executive director Mike Beck said. The project is estimated at $3.5 million, and a capital campaign for the project has raised about $2 million of its $4 million goal.

If all goes according to plan, the project will break ground in late fall, after the garden’s annual Harvest Festival, and open to the public next summer, Beck said.

The new conservatory will have a cross shape, with its four wings powered and heated largely with electricity from the garden’s own solar panels. The design will allow for presenting four different climate zones and a wider variety of plants and flowers. It's being designed by Smiemans Projecten, a Netherlands-based firm specializing in the design and construction of glass houses.

A 5,000 square foot glass house planned for Berkshire Botanical Garden in Stockbridge will allow for multiple exhibits of plants and flowers from different climates, as well as space for educational programs and special events.

The glass house will replace the older, run-down Lexan Greenhouse in the southern “education hub” section of the 24-acre campus. It’s seen as a key to growing the garden’s membership and revenues through year-round visits, educational programming and special events such as weddings.

Matthew Larkin, the chair of the nonprofit’s board of directors, is excited about finally remaining open to the public 12 months a year. He and Beck both said there’s potential in offering members and visitors a warm, vibrant place where they can escape the cold, gray skies of Berkshire winters and recharge.

The success of the annual bulb show in the Fitzpatrick Conservatory helped convince the board that there was demand for indoor winter programming, Larkin said. “Generally, around 1,000 people show up for that tiny little bit of spring,” he said.

“Imagine if we had this thing built for this [past] winter? We’d have lines out the door,” Larkin added. “It’s a refuge for people to be able to come and be in an enclosure, protected from the weather, that is beautifully warm and humid and filled with gorgeous plants. And my personal belief is for people who don’t have the opportunity to experience a real tropical garden or a real desert garden, we can create that kind of environment.”

The glass house is the last step in the first phase of a strategic plan completed for the garden by the landscape architecture firm of Nelson Byrd Woltz in 2019-20. Projects already completed include the construction of Mother Earth Lodge for summer camps, as well as an amphitheater and a wildflower meadow.

The new building will largely be powered and heated with electricity from the Berkshire Botanical Garden's 102 solar panels, with propane used as a backup for when electric power isn't enough. It's designed to be energy efficient, with double- and triple-glazed windows. "I am told on sunny winter days we won't have to kick the heater in at all," Beck said.

As an educational facility, the new glass house will provide the year-round space for classes and workshops that the garden has lacked, Beck said. As a destination, it will allow for four-season visits by members and visitors. It also will provide a space for weddings and special events, providing additional revenue.

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To this point the capital campaign for the glass house has happened behind the scenes, focusing on individual donors and foundations that have supported Berkshire Botanical Garden in the past. "That process has been happening the last 12-to-18 months, and we've had some great success already," Beck said. "We're closing in on about half the campaign raised or pledged."

According to Beck, the Berkshire Botanical Garden has about 1,600 members and welcomes about 40,000 visitors a year, with 25 percent of those visits coming during the annual Harvest Festival each fall. The organization has about 20 full-time staff.

He’s confident that once the glass house is complete, the Botanical Garden will grow its annual visitor count by 25 percent and increase its membership. He expects that revenue from visits, memberships and special events will pay for the additional employees needed to staff and maintain the new facility.

“As we expand the garden and staff we need to generate more income,” Larkin said. “We believe that the new glass house will not only be a great experience for visitors but will increase our membership numbers.”

Berkshire Botanical Garden, founded in 1934 as the Berkshire Garden Center with the bequest of 5 1/2 acres donated by Irene B. and Bernhard Hoffman, now sits on 24 acres of sculpted gardens and woodlands at the intersection of Routes 102 and 183 in Stockbridge. It was founded as a community resource to expand education and practical knowledge of horticulture at time when gardens were still widely considered a hobby for the well-heeled.

In addition to the Fitzpatrick Conservatory and dozens of sculpted gardens and walkways, the Botanical Garden also features the Leonhardt Galleries and annual events including Spring Fest, the Grow Show, the Fête des Fleurs garden gala, the Harvest Festival, the Rooted in Place Ecological Gardening Symposium, and a Holiday Marketplace.