Hermine Ricketts says she gardens for the food and for the peace it brings her. Greg Allen/NPR hide caption

itoggle caption Greg Allen/NPR

The Nourishmat, which is inspired by Square Foot Gardening, makes it easy to grow 15 to 20 pounds of food in a small space with a plastic mat that serves as a garden planting guide. Courtesy of Earth Starter hide caption

itoggle caption Courtesy of Earth Starter

Decorated gnomes designed by celebrities, including Elton John (second from the right), are displayed at Chelsea Flower Show on Monday in London. Dan Kitwood/Getty Images hide caption

itoggle caption Dan Kitwood/Getty Images

Through the City Land Application of Biosolids Program in Geneva, Ill., the fertilizer supplement is provided to local farmers at no cost. City of Geneva/Flickr hide caption

itoggle caption City of Geneva/Flickr

An urban farmer waters his plants near Bamako, Mali, where the government has set aside nearly 250 acres for market gardens. donkeycart/Flickr hide caption

itoggle caption donkeycart/Flickr

A tomato expert recommends planting seedlings in rich soil with lots of organic matter and a steady slow-release fertilizer. iStockphoto.com hide caption

itoggle caption iStockphoto.com

The lawn of Nashville yoga instructor James Alvarez is being taken over by buckwheat. Blake Farmer/Nashville Public Radio hide caption

itoggle caption Blake Farmer/Nashville Public Radio

One of the community gardens divided up into individual plots run by Denver Urb Gardens. Courtesy of Denver Urb Gardens hide caption

itoggle caption Courtesy of Denver Urb Gardens

D. Landreth Seed Co. President Barbara Melera with a bunch of peanuts at her Philadelphia Flower Show booth. Max Matza for NPR hide caption

itoggle caption Max Matza for NPR

Women's Correctional Community Center inmate Lilian Hussein checks on ti leaves she planted as part of the prison's farming and gardening program in Kailua, Hawaii. The green ti leaves are often used to wrap food or weave into leis. Jennifer Sinco Kelleher/AP hide caption

itoggle caption Jennifer Sinco Kelleher/AP

The new version of the map includes 13 zones, with the addition for the first time of zones 12 (50-60 degrees F) and 13 (60-70 degrees F). U.S. Department of Agriculture hide caption

itoggle caption U.S. Department of Agriculture