USDA Hardiness Zone

The USDA Plant Hardiness Zone Map divides the United States and Canada into 13 zones based on average annual minimum winter temperatures, with each zone representing a 10°F temperature range. The map is the standard reference for selecting plants that will survive winter conditions in any given location. Cannabis outdoor cultivation considerations: (1) Frost-free days — the period between the average last spring frost and average first fall frost determines the maximum outdoor cannabis growing season; this varies dramatically by hardiness zone, from 90 days in Zone 5 to 365 days in Zone 11; (2) Strain selection by zone — short-season zones (5-6) require fast-flowering autoflowers or early-finishing photoperiod strains (Critical Mass, Early Skunk, autoflowers); long-season zones (8-11) accommodate full-cycle sativas (Haze, Mexican landraces, full-cycle Sour Diesel); (3) Greenhouse extension — greenhouses can extend the outdoor cannabis season by 4-8 weeks in cooler zones, allowing later-flowering strains to finish before frost. US zones by major regions: Zone 5 (Minnesota, North Dakota, parts of New York and New England) — short season, frost-free 100-130 days; autoflowers strongly recommended; Zone 6 (most of New York, Massachusetts, Pennsylvania, Ohio, Iowa) — moderate season, 130-160 frost-free days; Zone 7 (New Jersey, Delaware, Maryland, Virginia, Tennessee) — good cannabis season, 160-190 frost-free days; Zone 8 (most of California, Oregon, Washington, North Carolina) — long season, 190-220 frost-free days; Zone 9 (Southern California, Arizona, Florida, Texas) — extended season, 220-280 frost-free days; Zone 10-11 (South Florida, Hawaii, Southern California coast) — year-round growing potential. Outdoor cannabis growers should look up their specific USDA zone (USDA zone finder by zip code) and select strains marketed for matching frost-free day windows. Royal King Seeds product pages include flowering time information that growers cross-reference with their local frost dates to ensure successful outdoor harvests before first fall frost.