Planting calendar
When to plant tomatoes in Colorado
Colorado spans USDA hardiness zones 3-7a. Average last spring frost: 05-15. This calendar gives you the indoor start, transplant, and direct-sow dates for Solanum lycopersicum.
Colorado planting dates for tomatoes
| Phase | Date in Colorado | Notes |
|---|---|---|
| Start seeds indoors | March 20 | 8 weeks before last frost |
| Transplant outdoors | May 29 | 2 weeks after last frost |
Why these dates
Tomatoes are warm-season crops that need 6-8 hours of direct sun and soil temperatures above 60F to thrive. Indeterminate varieties need staking or caging. Determinate varieties stay bushier and ripen all at once.
The dates above are anchored to Colorado's average last spring frost date of 05-15, with offsets standard across university Extension publications. For zone-specific local timing, use the frost date lookup tool with your ZIP code.
More on growing tomatoes
The full growing guide for tomatoes - varieties, soil, fertilization, pests, harvest, storage - is here: Tomatoes growing guide.
More Colorado planting information
- Full Colorado planting calendar (all crops + ornamentals)
- Find your exact USDA zone by ZIP
- Look up your average frost dates
- Seed starting timeline calculator