MANHATTAN — At least 15 community gardens on city-owned property could be bulldozed to make way for new buildings under the de Blasio administration's affordable housing plan, community advocates said.

The Department of Housing Preservation and Development published a list this week of city-owned sites that housing developers can apply to build on, shocking those who tend to and enjoy the green spaces.

Developers were asked to submit proposals for nearly 180 sites — which could include rentals for families earning nearly $140,000 a year and paying $3,000 in rent — by Feb. 19.

John McBride, one of the residents who helped Morningside Heights' Electric Ladybug Garden get off the ground, was surprised Thursday when he found the city had already padlocked his block's space.

"We were just getting ready to start planting for the spring and now it's padlocked," said McBride, 46, who was part of a two-year labor-intensive effort to clear rubble from the vacant lot on his West 111th Street block and replace it with clean topsoil from the Parks Department's Green Thumb this summer.

McBride said he understood the de Blasio administration's "huge commitment to housing," but he didn't understand why the city was targeting lots with flourishing gardens when it owned other parcels of land that were sitting truly fallow.

Of more than 1,000 HPD-owned vacant lots, approximately 74 have community gardens, according to research from 596 Acres, the nonprofit that helped provide technical support to transform Electric Ladybug.

Nine of the gardens slated for development are in Brooklyn and six are in Manhattan. They range from spots like East Harlem's Jackie Robinson Community Garden, which has been around for more than 20 years, to Williamsburg's La Casista Verde, which opened in September.

"We're not in denial about the terms of the use [since the garden sits on HPD land]," McBride said.

"What we're reacting to is a sense of misplaced priority. It would be so easy to avoid affecting these gardens when you look at HPD's inventory.

"This garden has allowed people to create a sense of community where it didn't exist before between the old timers and the newcomers. I think people are surprised at how quickly the garden has flourished. It's really given the block a positive tone."

Brenda Thompson, head of the Isabahlia Ladies of Elegance, a community group in Brownsville, didn't understand why the green space she helped revitalize a few years ago on Saratoga Avenue into "an educational garden" — with chickens, beehives and herbs like lemon balm and pineapple mint — was on the list while a vacant site a block away wasn't.

"It's really a community–based hangout and we'd be sad to see it leave," said Thompson, who runs community health workshops teaching people to use more herbs "to spice up meals" instead of salt.

Gardeners on city-owned land faced fierce opposition under the Giuliani administration. In 2002, the Bloomberg administration worked out a deal with then-Attorney General Eliot Spitzer which later led to more protections. But many gardens still faced threats from developers.

The city requires gardens looking to operate on HPD sites to provide a letter to the community board affirming it understands that they could only use it temporarily and that it won't hinder development plans, explained HPD spokesman Eric Bederman.

"Clearly we're open to allowing community groups to garden on HPD lots on an interim basis and we are sensitive to their concerns," Bederman said.

"While community gardens add a great value to our city, our mission as an agency is to address the affordable housing crisis that affects tens of thousands of hardworking New York families."

When the city requires an interim garden to move from an HPD site, the agency offers the group an opportunity to relocate to other sites within half a mile of the development or within the community district if available, he added.

"We’ve never been 100 percent protected, but it’s such a great space that I would really hate to see it be built up," said Alison Iven, 29, who helped found the Patchen Community Square in Bedford-Stuyvesant two years ago.

“The city hasn’t talked to us as a community garden yet, there’s not a lot of communication," she said.