GAZA — Hundreds of acres of watermelons, orange saplings and grapevines stretch in orderly rows out to the horizon. Irrigation hoses run along the sand, dripping quietly. Apple trees are starting to blossom nearby. Avocados and mangoes are on their way.

Gaza, cut off by Israel and Egypt for the past four years and heavily dependent on food aid, is expanding an enormous state-run farm aimed at gaining partial food independence. Most striking is that the project sits in the center of the coastal strip on the sites of the former Israeli settlements whose looted greenhouses and ruined fields became a symbol of all that had turned sour in the Israeli withdrawal six years ago.

Israel pulled out its 9,000 settlers and all of its soldiers from Gaza in 2005. The settlers’ high-tech greenhouses, which were bought for the Palestinians with $14 million in donations, were left unguarded and within days were stripped of computer equipment, irrigation pipes, water pumps and plastic sheeting.

Planting did resume, but after an attack on the border, Israel imposed security procedures on exiting trucks that left fresh produce baking in the sun, rendering it worthless. The greenhouse areas were abandoned and lay fallow, a symbol of hopelessness and hostility.

But in the past couple of years, as Gaza — ruled by the Islamist group Hamas — has struggled with its isolation and economic decline, the settlement areas have been reborn.

Renamed Al Muhararat — meaning the liberated lands — they make up 30 percent of the coastal strip’s land area. The farms on part of them, which are expanding every year, provide jobs for 500 people, as well as fruits and vegetables for large segments of Gaza’s 1.6 million inhabitants.

In food shops and market stalls across Gaza today, most of the onions, melons and grapes come from here. Last month alone, 100 tons of grapes and 23,000 tons of watermelons were produced. The greenhouses remain mostly stripped and unused, but the land under them is productive.

“We are making ourselves free of Israel economically and are on our way to food security,” Abdel Qader al-Astal, the director of the project, said in his office in what used to be the Israeli settlement of Gadid, renamed Al Yarmouk. In place of the usual spiced coffee served at meetings in the Arab world, slices of crisp apple and cucumber were passed around.

Out the window and across the field, Gadid’s former synagogue could be seen, a six-sided structure dear to the hearts of many former settlers. Today it is a mosque.

For the former Jewish settlers, who began coming here in the 1970s, the loss of their livelihoods and homes when the Israeli Army removed them remains a source of trauma. The way they mourn and remember their loss bears at times a striking resemblance to the way Palestinian refugees mourn theirs.

At a small museum at the entrance to Jerusalem named for the former settlement bloc, Gush Katif, that loss is on display: the keys to a former synagogue hanging on a wall, a cup of broken glass from its windows nearby and color photographs of smiling farmers in their greenhouses cultivating yellow peppers and geraniums.

Farming was the core of the settlers’ lives here. They provided 10 percent of Israel’s agricultural output and 65 percent of its organic greenhouse vegetables, exporting $25 million worth of produce annually. Many of those settlers remain in transitional housing inside Israel and in West Bank settlements. The failure of the Israeli government to resettle them properly has been yet one more argument offered in Israel against settler withdrawals for a Palestinian state.

A poem on the museum wall declares in part: “Katif is a wasteland now. A plot of splintered land, Attired in thorns and nettles, strewn with barren sand.”

That was the scene several years ago but is not now. The changes in the land come as no surprise to Shlomo Wasserteil, the founder and curator of the Gush Katif Museum and a former farmer here.

He knows about the shifts because he stays in touch with his former Palestinian workers. They have told him about the synagogue-turned-mosque, the rows of produce, the drip irrigation. The farmers themselves are considered by Hamas officials to be collaborators with Israelis so the farmers are not working on the government project here.

But some have farming jobs nearby and keep an eye on what is happening in the former Gadid. Next door, in what was the settlement of Gan Or, part of the fields has been renamed Mavi Marmara to honor the Turkish vessel that tried to break Israel’s naval blockade on Gaza 13 months ago and, after tussles onboard, ended with nine men dead at the hands of Israeli commandos.

Mr. Wasserteil has followed on-the-ground changes here, but presses for more details of his former home. In an echo of many Zionist accounts over the years, Mr. Wasserteil tells of what he and his fellow settlers found when they first arrived. “There was nothing but sand, not even a bird, like the Sahara. We produced the best tomatoes in the world. We revolutionized cultivation in sand and taught our neighbors in Jordan how to do it.”

He expressed surprising equanimity about the new developments. Asked how he felt about Hamas’s cultivations on his former fields, he said, “It depends what they do with what they produce. If it is to feed terrorists who then attack us, no thanks. But if it is to feed the people who live there and they can learn to be good neighbors, that’s good.”

James Wolfensohn, a former president of the World Bank who served as international representative to the conflict at the time of the handover, was the one who raised the $14 million for the greenhouses. He called friends like Bill Gates. Mortimer B. Zuckerman, the publisher of The Daily News, threw in a bit of his own, and in a few weeks he had the money.

“There was nothing but hope then,” Mr. Wolfensohn said when reached by telephone in London. “We thought about tourism and hotels and turning Gaza into the Arab Riviera.”

But between the looting, security delays and corruption of border guards — both Israeli and Palestinian, he noted — and then after Israel’s three-week offensive in 2008-9 and the naval blockade, the economy fell apart.

Told of the newly revived farmlands, he was delighted.

“It saddened me that something I thought was a really good contribution had gone sour,” he said. “I thought if people were vested in the economics of their activities and there was interdependence between Israelis and Palestinians, the risk of violence would be greatly reduced. The area would flourish. But the problem with the Middle East is that it is not always rational.”