The 5 fields and concepts you'll meet in the response — defined in plain English, each with a real example value.
A geographic area defined by its average annual minimum winter temperature, used to determine plant survival.
The USDA divides North America into 13 zones, each spanning 10°F. Plants are rated by which zones they can survive. Zone 1 is coldest, Zone 13 is warmest. Most gardening guidance references these zones.
ExampleZone 7b: 5°F to 10°F average minimum
The average lowest temperature reached each year, used to define hardiness zones.
Hardiness zones are calculated from 30 years of minimum temperature data. The average annual extreme low determines which zone a location falls into. This predicts whether perennial plants will survive winter.
ExampleZone 6a: -10°F to -5°F minimum
The average date of the last spring frost or first fall frost in a location.
Frost dates complement hardiness zones for planting guidance. The last spring frost date indicates when to transplant frost-sensitive plants outdoors. First fall frost date indicates the end of the growing season.
ExampleLast frost: April 15, First frost: October 20
A localized climate that differs from the surrounding area due to terrain, structures, or other factors.
South-facing walls, urban heat islands, low-lying frost pockets, and wind shelters create microclimates. Your yard may be warmer or colder than the official zone suggests. Experienced gardeners learn their specific microclimates.
ExampleA sheltered south-facing wall acting as Zone 7 in a Zone 6 area
A plant that lives for more than two years, surviving winter and regrowing each spring.
Perennials must survive winter in their hardiness zone. They die back in fall and regrow from roots in spring. Trees, shrubs, and many flowers are perennials. Hardiness zones primarily apply to perennial plant selection.
ExampleHostas, daylilies, and fruit trees are perennials
