WASHINGTON - Michelle Obama will begin digging up a patch of the South Lawn on Friday to plant a vegetable garden, the first at the White House since Eleanor Roosevelt’s victory garden in World War II.

While the organic garden will provide food for the first family’s meals and formal dinners, its most important role, Michelle Obama said, will be to educate children about healthful, locally grown fruit and vegetables at a time when obesity and diabetes have become a national concern.

Twenty-three fifth graders from Bancroft Elementary School in Washington will help her dig up the soil for the 1,100-square-foot plot, in a spot visible to passers-by on E Street. (It is just below the Obama girls’ swing set.)

Students from the school, which has had a garden since 2001, will also help plant, harvest and cook the vegetables, berries and herbs.

Virtually the entire Obama family, including the president, will pull weeds, “whether they like it or not,” Mrs. Obama said with a laugh.

“Now Grandma, my mom, I don’t know.” Her mother, she said, will probably sit back and say: “Isn’t that lovely. You missed a spot.”

Promoting healthful eating has become an important part of Mrs. Obama’s own agenda.

The first lady, who said that she had never had a vegetable garden, recalled that the idea for this one came from her experiences as a working mother trying to feed her daughters, Malia and Sasha, a good diet.

Eating out three times a week, ordering a pizza, having a sandwich for dinner all took their toll in added weight on the girls, whose pediatrician told Mrs. Obama that she needed to be thinking about nutrition.

“He raised a flag for us,” she said, and within months the girls had lost weight.

Dan Barber, an owner of Blue Hill at Stone Barns, an organic restaurant in Pocantico Hills, N.Y., that grows many of its own ingredients, said: “The power of Michelle Obama and the garden can create a very powerful message about eating healthy and more delicious food. I don’t think it’s a stretch to say it could translate into real change.”

While the Clintons grew some vegetables in pots on the White House roof, the Obamas’ garden will far transcend that, with 55 varieties of vegetables - from a wish list of the kitchen staff - grown from organic seedlings started at the Executive Mansion’s greenhouses.

The Obamas will feed their love of Mexican food with cilantro, tomatillos and hot peppers. Lettuces will include red romaine, green oak leaf, butterhead, red leaf and galactic. There will be spinach, chard, collards and black kale. For desserts, there will be a patch of berries. And herbs will include some more unusual varieties, like anise hyssop and Thai basil.

A White House carpenter, Charlie Brandts, who is a beekeeper, will tend two hives for honey.

The total cost of seeds, mulch and so forth is 200 dollars, said Sam Kass, an assistant White House chef, who prepared healthful meals for the Obama family in Chicago and is an advocate of local food. Kass will oversee the garden.

The plots will be in raised beds fertilized with White House compost, crab meal from the Chesapeake Bay, lime and green sand. Ladybugs and praying mantises will help control harmful bugs.

Cristeta Comerford, the White House’s executive chef, said she was eager to plan menus around the garden, and Bill Yosses, the pastry chef, said he was looking forward to berry season.

The White House grounds crew and the kitchen staff will do most of the work, but other White House staff members have volunteered. (ANI)