The newest crop at Down Island Farm in Tisbury wasn’t planted. It doesn’t need pruning or watering, and it’s not susceptible to disease or pests. But as with any crop, it needs a little help from the sun.

Actually, a lot of help from the sun as sunlight does the hard part, baking the small hoop house in Heidi Feldman and Curtis Friedman’s backyard so that the ocean water collected in a wide, shallow pan evaporates. What remains are coarse salt crystals that glint when the light hits them just so.

“That’s untinkered with, that’s what nature produces for us,” Ms. Feldman said in an interview on Tuesday. “We don’t sift it or anything. It is what it is.”

Mr. Friedman works as a carpenter for South Mountain Company and Ms. Feldman as a technical consultant. In their spare time last summer, the two built evaporator prototypes and made test batches of salt. There is only one hoop house at Down Island Farm for now, but by next summer they hope to be in full operation as Martha’s Vineyard Sea Salt. They have begun preparations for constructing larger salt pans and evaporating structures, and expect to have the first retail batch of salt ready in mid-2013.

Inside the evaporator.

Ivy Ashe

Inside the evaporator.

Ivy Ashe

The idea for Martha’s Vineyard Sea Salt was born two years ago.

“Honestly, I just kept going back to what’s sustainable, what will the local people want, what’s something nobody’s thought of, what’s something you use every day,” Ms. Feldman said. When she and her husband began farming in 2004, they realized their land, with its dense oak groves and rocky soil, wasn’t suited for traditional crops. They began cultivating shiitake mushrooms. Shiitakes grow inside oak trees, making them a natural choice. That endeavor worked well for a time, as the mushrooms were especially popular with local restaurants. But a two-year plague of winter moth caterpillars killed off many of the oaks and contaminated the shiitakes.

“All of a sudden everything’s back up in the air again,” Ms. Feldman remembered. She had been growing nasturtiums and other edible flowers for Island businesses, but could not make a living from that garden. The idea of creating a local product and contributing to the farm economy nevertheless persisted, and one day in July, she had “a moment” while snacking on a bag of vinegar and sea salt potato chips.

“It just dawned on me — sea salt,” Ms. Feldman said.

Sea salt, unlike table salt, is not processed, meaning it retains traces of minerals and nutrients. According to the American Heart Association, it has the same amount of sodium — about 40 per cent — as table salt. The two have starkly different textures, and different uses for chefs and restaurants. Table salt, for example, blends much easier into mixtures, while the coarseness of sea salt makes it a distinctive seasoning choice.

But salt isn’t used just in the kitchen. Sea salt is a favorite of those in the equestrian business as horses need extra sodium in their diet which they can’t get from hay alone. Martha’s Vineyard Sea Salt has orders already from many Island horse owners and from a Florida-based equine supplement company. And the first batch of salt made at Down Island Farm went to a local potter, who mixes it with his clay to add texture. That batch is “fondly called protein salt,” Ms. Feldman said, because of the bugs that wandered in during the evaporating process. Screens have since been added to the hoop house. They are also now formally licensed by the Massachusetts Board of Health.

To harvest the salt, seawater is collected from the south shore of the Island, which is less trafficked by boats and less subject to runoff concerns. It is poured into a one-inch deep evaporator created with black food-grade liner, then left to its own devices in the hoop house for three to five weeks, although the exact duration varies depending on overall temperatures and weather conditions. Solar gain is at its peak during the summer months, and Ms. Feldman said she expects their harvesting season to be from April to mid-October. She’s making a test batch now that was started last month, but evaporation comes slower in the colder months.

Just as the evaporation process starts, a thin film of salt forms on the water surface. This is called fleur de sel (flower of salt), and is considered to be the best salt. It has the fineness of table salt and the mineral content of sea salt. Eventually, Down Island Farms hopes to refine a process of harvesting and selling the fleur de sel as well.

Once Ms. Feldman and Mr. Friedman had made the decision to harvest salt, they experimented with drying and baking the salt in their kitchen, but quickly realized that process used too much fuel and petroleum to be a sustainable product.

“Plus,” Ms. Feldman said, “the salt tastes weird if you do it that way . . . if you don’t do it long, low and slow, you’re going to get this burnt, sour flavor.”

Solar, it seemed, was the way to go. This was confirmed after a trek to Maine Sea Salts in Machias, Me., where Stephen Cook has been selling harvested sea salt nationally since the 1980s. Mr. Cook’s salt is produced in the exact same way as Down Island Farms, except on a larger scale

“The guy is as nice and as real and as great of a role model as you could want,” Ms. Feldman said. “We went to the mecca of salt.”

Besides getting advice from the pros, Ms. Feldman and Mr. Friedman turned to family and friends for suggestions — and to help sample the salt. A tray of “research salts” sent from other saltmakers sits in the Down Island Farms kitchen, containing everything from citrus sea salt to lemon ginger salt. There is also a prototype of a blueberry-honey mix that Ms. Feldman is testing with her own salt.

“It’s really important to me to feature indigenous flavors,” she said.

Incorporating community into the product is imperative for the Down Island Farms business plan. The small muslin bags that Martha’s Vineyard Sea Salt will be sold in are produced by Ecobags, a fair-trade, fair-labor company owned by Ms. Feldman’s sister. Jesse Hayes, owner of Hayes Design Studio in Edgartown, designed the logo and business cards, which were printed at the Tisbury Printer.

And as for the snack that inspired it all, there are no plans to go into potato chips yet. But the salt will be used for another munchable treat: next season it will be the house salt for the popcorn at the Martha’s Vineyard Film Center.