Here is just a bit of the research:
“FDR’s Federal Emergency Relief Administration paid gardeners to grow and distribute produce to needy people. Individual gardening programs also blossomed in cities around the country. In New York City, a gardening campaign orchestrated by the welfare department and assisted by the Works Progress Administration turned over 5,000 vacant lots into flourishing gardens. These gardens generated $5 worth of vegetables for every dollar invested, resulting in $2.8 million worth of food by 1934. Ornamental gardens, culinary gardens, and medicinal gardens sprang up around the country as part of various civic projects. The Herb Garden in the Brooklyn Botanical Garden was created by WPA laborers, as were the exquisite Boerner Botanical Gardens near Milwaukee.”http://www.revivevictorygarden.org
“During World War I and World War II, the United States government asked its citizens to plant gardens in order to support the war effort. Millions of people planted gardens. In 1943, Americans planted over 20 million Victory Gardens, and the harvest accounted for nearly a third of all the vegetables consumed in the country that year. Emphasis was placed on making gardening a family or community effort -- not a drudgery, but a pastime, and a national duty.”