Large donors expected to fund botanical garden

Massachusetts Horticultural Society officials said yesterday they expect to draw on a few large donors, probably from biotechnology firms and conservation organizations, to pay for a new botanical garden and learning facility on Boston's Surface Artery.

At the first public presentation of the Darwin Project, the society's new idea for an enclosed public garden on the former Central Artery corridor near South Station, project codirector Linda M. Haar estimated the cost at $60 million to $70 million.

Fund-raising to construct a glassed-in main building, various other structures, and extensive gardens on three blocks of land on the Rose Kennedy Greenway won't begin for at least a year, Haar told a meeting of the Central Artery Environmental Oversight Committee.

But, as designs are sketched and planning for activities at the facility proceeds over the next one to two years, a capital campaign will begin to collect funds for construction and to endow operations.

''We will be looking at the biotech and technical businesses to support this -- also national and international communities connected to conservation," Harr said. ''It will be a few very large donors that will support this project." She would not be more specific, saying the size and cost of the final project are a long way from being determined.

Visitors will also be needed to keep things running. Admission will be ''as free as possible," Haar said. ''Ultimately there will probably have to be some kind of charge."

Boston Mayor Thomas M. Menino and Massachusetts Turnpike chairman Matthew J. Amorello will help launch a campaign for public support and planning money on Tuesday.

After years of inaction and failed attempts by the horticultural society and its subsidiary, Garden Under Glass Inc., Haar and her husband, Jonathan, principals of the Boston Planning Institute Inc., three months ago were named codirectors of the project.

Rather than focusing on building construction and leaving decisions about its use for later, the Haars have focused on activities on the 3.1 acres, which were designated for Massachusetts Horticultural Society use more than a decade ago.

Their proposal, termed the Darwin Project at least until major sponsors are signed on, includes an updated version of a Victorian botanical garden, a ''biodiverse" collection of plant species and other small life, and a learning center for children and adults.

The project is being conceived as a place to bring people together, like the Boston Common. ''You might say this is the indoor Common," Haar said.

Rob Tuchmann, cochairman of the Environmental Oversight Committee, welcomed details of the project after years of inaction that was discouraging to people hoping for a long-planned, post-Big Dig ''winter garden."

''This is just the breath of fresh air we've been waiting for for 12 years or so," Tuchmann said. Details of the project are available on its developing website, www. darwinboston.org.

Thomas C. Palmer Jr. can be reached at tpalmer@globe.com.