When to Plant Cabbage in Colorado
Published: April 24, 2026
Colorado gardeners in Zone 6a have a 31-week growing season for cabbage (March 30 to November 1). Colorado's spring and fall windows both work well for cabbage — some gardeners plant both successions for a long harvest. This guide gives exact dates for Colorado based on your local frost calendar.
Cabbage Planting Dates for Colorado
| Start seeds indoors | February 9–16 |
| Last frost (average) | March 30 |
| Transplant outdoors | March 9–19 |
| Expect first harvest | May 8 – June 17 |
| Fall crop start | August 9–19 |
| Fall harvest | October 8 |
| First fall frost (average) | November 1 |
Dates above assume Zone 6a, the most common zone in Colorado. Gardeners in cooler Denver (Zone 6a) plant 1–2 weeks later; warmer Colorado Springs (Zone 6b) can plant 1–2 weeks earlier.
⚠ Start cabbage indoors 6–8 weeks before last frost. Transplant 2–4 weeks before last frost. Very frost tolerant — withstands temperatures as low as 20°F. Also plant in late summer for fall harvest.
Growing Cabbage in Colorado's Climate
Colorado's moderate Zone 6a climate is well-suited to cabbage with minimal special accommodation. The standard transplant calendar works as written, and harvest windows line up with what seed packets recommend without adjustment.
Succession planting extends your cabbage harvest significantly in Colorado. A second planting 3 to 4 weeks after the first gives you a backup in case of pest pressure and extends the total harvest window into early fall.
Common cabbage pests to watch for in Colorado include Cabbage Worm and Cabbage Looper. The first line of defense is companion planting: Onion and Dill planted nearby discourage several of these pests by confusing host-plant identification or repelling adults before they can lay eggs. Weekly garden walks in the early morning catch problems when they're still manageable.
Cabbage Garden Calendar for Colorado
| Month | Task | Notes |
|---|---|---|
| January | — | Dormant season |
| February | Start seeds indoors | Use grow lights; warm soil to 70–75°F for best germination |
| March | Transplant outdoors | Soil temp must be 45°F+; nighttime lows above 50°F |
| April | — | Dormant season |
| May ← | Watch for bolting | Harvest promptly; spring heat arrives quickly |
| June | — | Dormant season |
| July | — | Dormant season |
| August | Fall crop planting | Transplant or direct sow for fall harvest before frost |
| September | — | Dormant season |
| October | — | Dormant season |
| November | First frost approaches | Harvest remaining cabbage; cover plants on frost nights |
| December | — | Dormant season |
Cabbage Growing Tips for Colorado Gardeners
- •Space plants 18 inches apart — crowding reduces head size and promotes fungal disease.
- •Side-dress with nitrogen 3–4 weeks after transplanting to support rapid leaf formation.
- •Colorado's moderate climate supports succession planting — sow new transplants or seeds every 3 weeks during spring to extend the harvest window into fall.
- •Harvest when heads feel firm; leave the root ball in the ground and small secondary heads may form.
Companion Planting for Cabbage in Colorado
In Colorado's moderate climate, planting cabbage with Onion and Dill helps deter pests and improve soil. Avoid planting near Tomato and Strawberry, which inhibit cabbage growth through root chemistry or shared pest pressure. See the full cabbage companion planting guide for the complete list.
Cabbage Planting Dates by City in Colorado
Top cities in Colorado — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant cabbage in Colorado?
In Colorado (Zone 6a), start cabbage seeds indoors around February 9–16 and transplant outdoors around March 9–19 — 3 weeks before the state's average last frost of March 30.
What is the last frost date in Colorado?
Colorado's average last frost date is March 30 in the state's most common Zone 6a. Frost dates vary by city — higher elevations and northern counties run 1 to 3 weeks later than the state average. See the city list below for city-level frost dates.
Can I grow cabbage year-round in Colorado?
cabbage is a cool-season crop in Colorado, with spring and fall windows. Summer heat bolts the plants before they can produce a harvestable crop. Succession planting every 2–3 weeks stretches the harvest window.
What cabbage varieties grow best in Colorado?
For Colorado's Zone 6a, consult a local nursery or extension office for cabbage variety recommendations.
When do I start cabbage seeds indoors in Colorado?
Start cabbage seeds indoors in Colorado around February 9–16, which is 7 weeks before the state's average last frost of March 30. Use grow lights and keep soil temperatures at 70–75°F for fastest germination.