WASHINGTON — In another sign that the Department of Agriculture is embracing sustainable food, the agency has unveiled expanded plans for a People's Garden that will include the entire six-acre grounds of the Whitten Building, the department's neoclassic marble headquarters on the Mall.

The plans, announced at the agency's Earth Day celebrations, include a 1,300-square-foot organic vegetable garden — slightly larger than the one at the White House — as well as ornamental flower gardens and bioswales, or mini-wetlands designed to reduce pollution and surface water runoff. The building grounds now are landscaped with grass, flower borders and trees planted to honor a person or mark an event.

Secretary Tom Vilsack, an avid runner, came up with the idea for the garden during one of his daily runs around the Mall. He noticed tourists stopping to look at the trees and their dedication plaques. A thriving garden, he thought, would be a better way to communicate the agency's mission of sustainability and in particular the importance of fresh fruits and vegetables, a cornerstone of the agency's push to improve school nutrition and reduce childhood obesity.

MORE THAN SYMBOLIC

Initial plans were announced at a groundbreaking in February on Abraham Lincoln's birthday. Lincoln founded the Department of Agriculture in 1862 and referred to it as the People's Department, hence the name People's Garden.

Originally, Vilsack, 58, envisioned a vegetable garden only half the size and a goal to have at least some type of garden — even if just a window box — at every USDA facility. But in a recent interview at his office, which overlooks the scrubby lawn, Vilsack said the positive public response to the idea and a March meeting with horticulture and garden groups persuaded him to broaden the plan. The garden now will encompass all of the agency's property on the Mall, and the department will work with organizations nationwide to encourage individuals, schools and communities to establish gardens.

"If we can get people to focus on fruits and vegetables and more healthy foods, we'll be better in terms of our healthcare situation," Vilsack said. Exposing visitors to model ecosystems, such as the bioswales, is also "important as we transition to a discussion about climate change and green jobs and all the issues involved in the environment."

The organic vegetable garden will feature a rotation of crops, beginning with cool-weather plants such as field peas, lettuce, spinach and kale. As summer approaches, tomatoes, peppers, squash and herbs, among other things, will be planted.

There will also be a three sisters garden, a traditional Native American planting method in which corn, pole beans and squash are grown together. The beans fix nitrogen, a fertilizer, in the soil and use the cornstalks as natural poles to climb. Squash has big leaves that shade the soil, keeping it moist and cutting out light that would allow weeds to grow. The chairman of the Cheyenne River Sioux of South Dakota participated in a planting ceremony and exchange of seeds with USDA Deputy Secretary Kathleen Merrigan at the Earth Day event.

All vegetables produced will be donated to a local food bank. But the garden's primary role is education. Gardeners will work toward winning it organic certification; signs and possibly a video at the USDA visitors' center will explain the process and benefits of organic agriculture. The vegetables will be grown in three ways: in the ground (the soil has been tested several times and contains no chemical residues), in raised beds and in containers. The goal is to illustrate the many ways to grow food, dispelling the notion that gardeners need large plots of land.

SUSTAINABILITY KEY

The emphasis on gardening might surprise some sustainable-agriculture advocates, who initially greeted Vilsack's appointment with skepticism. A former governor of Iowa, Vilsack had close ties to conventional farmers and ranchers and had supported biotechnology and ethanol. But in his first 91 days, the secretary has made efforts to win food advocates' trust. He has met with progressive farm groups and food policy organizations and watched a screening of "Food Inc.," an indictment of the industrial food system, with authors Eric Schlosser and Michael Pollan, two leaders of the sustainable-food movement.

The new garden has provided another chance to include new voices, Vilsack said. In March, he convened a meeting in Washington at which 47 gardening and horticulture organizations, including the Rodale Institute, Seed Savers and the American Community Gardeners Association, offered feedback and brainstormed ways to spread the message.

"I kept having to pinch myself in this meeting," said Rose Hayden-Smith, a historian and food systems educator for the University of California. "We're not the kind of people who have been invited to Washington, D.C., before. We're the guerrilla gardeners, the pollinator people, the seed savers. It wasn't our usual cast of characters. People were grinning from ear to ear."