How bloom timing works by zone
Bloom time shifts about 2 weeks per USDA zone. A peony that blooms in early May in zone 7 (Long Island) blooms in late May in zone 5 (upstate NY) and mid-April in zone 8 (coastal Carolina). Per Penn State Extension, the standard rule for spring bulbs is that one zone equals roughly 14 days of bloom shift, with elevation and microclimate adding to the delay.
This tool starts from broad bloom seasons (spring, summer, fall) in each plant's database entry, then maps to calendar months based on your zone:
- Spring bloomers in zone 3 → May/June; zone 5 → April/May; zone 7 → March/April/May; zone 9 → February/March
- Summer bloomers in zone 3 → July/August; zone 5 → June/July/August; zone 7 → May/June/July/August; zone 9 → April-October
- Fall bloomers in zone 3 → August/September; zone 5 → August/September/October; zone 7 → September/October; zone 9 → October/November
For more precision, cross-reference with our frost dates tool and your local extension office's bloom calendar.