USDA Plant Hardiness Zones are based only on the minimum average temperature. Using this scale, California spans from zone 5a, where average annual minimum temperatures are between -20 and -15 ...

A strict 'Zone 0' rule against landscaping is risky. Well-maintained and watered vegetation could prevent the spread of fires ...

Knowing when to plant in specific hardiness zones is important to maximize the spring season's potential. A hardiness zone is a geographic area with a similar average minimum temperature.