When he wasn’t busy manning the family department store, Doug Dayton would put on his straw hat and wander into the colorful prairies and orchard surrounding the home he built near downtown Wayzata almost 50 years ago.

Now, nearly a year since his death, the 93-acre estate is on the market, and there’s a long line of developers willing to pay top dollar for a chance to carve the property into numerous sites for luxury homes.

But Dayton’s widow, Wendy, is determined to keep them away. She plans to sell the property at a colossal discount to a buyer willing to restrict development on the land that her late husband, who founded the Target discount chain, worked so hard to cultivate.

“We have to preserve the land because there isn’t any more of it,” Wendy Dayton said. “Anybody buying this house will have to understand the responsibilities that go along with it.”

With homebuilding on the rebound and prime development sites dwindling, developers across the Twin Cities metro are outbidding each other for raw land, especially in the inner-ring suburbs where new-home sales are the most robust. Last month, sales of upper-bracket homes were up nearly 30 percent and several large parcels, including a handful of golf courses, are being redeveloped for high-end housing.

Doug and Wendy Dayton, however, had long discussed ways of preventing this from happening to their estate. The current plan calls for an 83-acre conservation easement with the ­Minnesota Land Trust that allows three small parcels for future construction.

“This is a very rare opportunity,” said Kris Larson, the land trust’s executive director. “Clearly, it is one of the larger undeveloped parcels in that area.”

When word leaked that the property was coming to market, developers pounced. Meredith Howell, the Coldwell Banker Burnet agent who has the listing, received several unsolicited offers long before it hit the market for $5.9 million, far less than it would be worth as a redevelopment project.

“On the first day on MLS, I had a couple of agents who hadn’t seen the property, but said they were sending a purchase agreement,” Howell said.

Because of the risk of redevelopment, those offers went nowhere. Howell said the property is priceless and is being sold for millions of dollars less than what it’s really worth.

Aside from the 6,600-square-foot house that’s tucked into the side of a hill overlooking more than 1,600 feet of shoreline on a private lake, the estate offers complete privacy less than 15 minutes from downtown Minneapolis.

“And this is right at Wayzata’s back door,” Dayton said. “This was Doug’s dream, and it is a gift to the community to have its beauty remain.”

Doug Dayton was the grandson of Dayton’s department store founder George D. Dayton. He served as a company executive and is credited with launching Target. In his later years, he was a venture capitalist, small-business owner and a longtime volunteer and ­philanthropist.

He preferred the tranquility of the woods and prairies to the social buzz that many of his financial ilk sought in the Great Gatsby-style mansions along the shores of Lake Minnetonka. Inspired by his own childhood summers at the Dayton family’s secluded Boulder Bridge Farm on Lake Minnetonka, he started acquiring land for what he called his “Shangri-la” when he was in his 30s and commissioned architect Robert Bliss to design a sprawling ranch home on a knoll overlooking the lake.

Dayton’s goal was to restore the fields to what they might have looked like before it was farmland, and he cultivated nearly 40 acres of waving grasslands and knotted walking trails through a basswood maple forest.

He was hands-on, and helped plant the prairies, dozens of fruit trees and 50 ­willows that, until recently, swept over the winding driveway. He relished the return of a pair of nesting ospreys every summer.

“Being there is a gift,” said Jim Williams, a well-known Twin Cities birder who lives just down the street from the property. After watching critical wildlife habitat in the area give way to “five-acre estates,” Williams said, he asked Dayton if he could start bird-watching on the property. “He opened the entire piece to me without restriction,” said Williams. “It would be heartbreaking to see it put to a grader.”

Increasingly, that’s what’s happening in the Twin Cities suburbs.

Pat Hiller, a principal with Plymouth-based Source Land Capital, said that in nearby Plymouth, developable land is selling for more than $200,000 an acre, and Source Land recently spent millions on two golf courses that will become housing developments.

The 21-acre Red Oaks course in Minnetrista was recently replatted into nearly 60 lots and sold to a national housing developer, and Source Land is seeking municipal approval to redevelop the Lakeview Golf Course in nearby Orono into about 55 two-acre homesites.

“Demand exceeds supply,” Hiller said. “Every developer in town would love to have that 100-acre piece of [Dayton] property.”

Wendy Dayton’s efforts come in the wake of an obscure new law that eliminates an important incentive for easement donations.

With development marching across the Twin Cities, easement agreements have become a popular way of preserving open space, but a key catalyst for such deals was eliminated in late 2013 when a new law said the value of a property enrolled in a conservation easement cannot be reduced by county assessors. Minnesota is the only state in the nation to pass such a law, which was tucked into a broader tax package.

Larson said that he’s pursuing discussion with legislators about repealing the law and that it’s too soon to tell how much an impact the new guidelines will have on future easements. “We’re very concerned,” he said.Meanwhile, Dayton is undeterred in her commitment to the easement, and hopes to find a buyer who will see the development restriction as an asset.

Weeks before Doug Dayton died on July 5 last year, he hopped on his Kawasaki Mule one last time with his longtime property manager, Stephen Steinborn.

With bees buzzing through the prairie and quiet breezes sweeping through tall cottonwood trees where a pair of redtail hawks now nest, Dayton was thrilled to see the native lupines — one of his favorite plants — in full bloom.

“He was out here every chance he got,” Steinborn said. “He was glad to know it would be like this forever.”