Colorado’s high altitude and intense sunlight create unique conditions for timing cabbage planting. The best time to plant cabbage in Colorado depends on your specific region and the last frost date in spring.
Cabbage is a cool-season crop that thrives in temperatures between 45°F and 75°F. In Colorado, the growing season is short in many areas, so timing is everything.
This guide covers everything you need to know about planting cabbage at the right time for a successful harvest. We’ll look at spring and fall planting, frost dates, and variety selection.
Understanding Colorado’s Climate For Cabbage
Colorado’s climate is challenging for many vegetables, but cabbage can handle it well if planted at the right time. The state has USDA hardiness zones ranging from 3 to 7.
Higher elevations have shorter growing seasons and cooler nights. Lower elevations, like the Front Range, have longer summers but still experience temperature swings.
Cabbage needs consistent moisture and cool soil to germinate and grow. Hot weather causes it to bolt or form loose heads.
Key Climate Factors For Cabbage
- Last spring frost: Varies from late April to late May depending on elevation
- First fall frost: Can occur as early as mid-September in mountain areas
- Soil temperature: Cabbage germinates best at 45°F to 85°F
- Day length: Longer days in summer can stress cabbage
Knowing your local frost dates is the first step. Check with your county extension office or use an online frost date calculator.
Best Time To Plant Cabbage In Colorado
The best time to plant cabbage in Colorado is early spring, about 4 to 6 weeks before the last expected frost. For most of the state, this means planting seeds indoors in late February or early March.
Transplants can go into the garden 2 to 4 weeks before the last frost. This gives cabbage time to mature before summer heat arrives.
For a fall harvest, plant cabbage in mid-to-late summer. Aim for 6 to 8 weeks before the first fall frost. This works well in lower elevations where summers are hot.
Spring Planting Schedule By Region
Colorado is large, so timing varies. Here is a general guide for spring planting:
- Denver and Front Range (Zone 5-6): Start seeds indoors mid-March. Transplant outdoors mid-April to early May.
- Colorado Springs (Zone 5): Start seeds indoors early March. Transplant outdoors late April.
- Mountain areas (Zone 3-4): Start seeds indoors late February. Transplant outdoors mid-May to late May.
- Western Slope (Zone 6-7): Start seeds indoors early March. Transplant outdoors early April.
Always adjust based on your microclimate. A cold pocket in your yard can delay planting by a week or more.
Fall Planting Schedule
Fall cabbage is often sweeter because cool weather increases sugar content. Plant for fall harvest in these windows:
- Denver area: Late July to early August
- Colorado Springs: Mid-July to early August
- Mountain areas: Early to mid-July
- Western Slope: Late July to mid-August
Fall planting requires careful timing. If you plant too late, heads may not form before frost. If you plant too early, heat can stunt growth.
How To Start Cabbage Seeds Indoors
Starting seeds indoors gives you a head start. It also protects young plants from late frosts and pests.
- Fill seed trays with a sterile seed-starting mix
- Sow seeds ¼ inch deep, 2 to 3 seeds per cell
- Water gently and cover with plastic wrap to retain moisture
- Place in a warm spot (65°F to 75°F) until germination
- Once seedlings emerge, move to a bright location with cooler temps (55°F to 65°F)
- Thin to one strong seedling per cell after true leaves appear
Harden off seedlings before transplanting. This means gradually exposing them to outdoor conditions over a week. Start with a few hours of shade, then increase sunlight and wind exposure.
When To Transplant Cabbage Seedlings
Transplant when seedlings have 4 to 6 true leaves and are about 4 to 6 inches tall. The soil should be workable and not waterlogged.
Space plants 12 to 24 inches apart, depending on the variety. Rows should be 24 to 36 inches apart. Cabbage needs room for head development.
Water transplants well and provide shade if the weather is sunny. A floating row cover can protect against pests and temperature swings.
Soil Preparation For Cabbage
Cabbage grows best in well-drained, fertile soil with a pH between 6.0 and 7.5. Colorado soil is often alkaline, so you may need to adjust pH.
Test your soil before planting. Add compost or well-rotted manure to improve organic matter. Cabbage is a heavy feeder, so incorporate a balanced fertilizer before planting.
Work the soil to a depth of 8 to 10 inches. Remove rocks and debris. Cabbage roots are shallow, so loose soil helps them spread.
Fertilizing Cabbage
Cabbage needs nitrogen for leaf growth. Apply a nitrogen-rich fertilizer at planting time. Side-dress with more nitrogen when heads begin to form.
Use a fertilizer like 10-10-10 or 5-10-10. Follow package rates. Too much nitrogen can cause lush leaves but small heads.
Consider using a slow-release organic fertilizer. It provides nutrients steadily without burning roots.
Direct Sowing Cabbage Seeds Outdoors
You can also sow cabbage seeds directly in the garden. This works best for fall crops or in areas with long springs.
Direct sow seeds 2 to 4 weeks before the last frost. Soil temperature should be at least 40°F. Seeds germinate slowly in cold soil.
Sow seeds ½ inch deep, 2 to 3 seeds per spot. Thin to one plant per spot after germination. Space plants as recommended for transplants.
Direct sowing is less predictable than transplants. But it avoids transplant shock and can produce strong plants.
Watering Cabbage In Colorado
Colorado’s dry climate means cabbage needs regular watering. Cabbage is about 90% water, so consistent moisture is critical.
Water deeply 1 to 2 times per week, depending on weather. Aim for 1 to 1.5 inches of water per week. Use a soaker hose or drip irrigation to keep leaves dry.
Mulch around plants with straw or grass clippings. Mulch conserves moisture, cools the soil, and suppresses weeds.
Inconsistent watering causes heads to crack or become tough. Check soil moisture by feeling 2 inches below the surface.
Pest And Disease Management
Cabbage faces several pests in Colorado. The most common are cabbage worms, aphids, and flea beetles.
Use row covers to exclude pests. Apply insecticidal soap for aphids. Handpick cabbage worms or use Bt (Bacillus thuringiensis).
Rotate crops to prevent soil-borne diseases. Avoid planting cabbage where other brassicas grew in the past 3 years.
Watch for clubroot, a fungal disease that causes swollen roots. Improve drainage and avoid overwatering to prevent it.
Common Cabbage Varieties For Colorado
Choose varieties that mature quickly and tolerate temperature swings. Here are good options:
- Early Jersey Wakefield: Heirloom, matures in 60-70 days, cone-shaped heads
- Golden Acre: Compact, matures in 65-75 days, good for small spaces
- Red Acre: Red cabbage, matures in 75-80 days, stores well
- Savoy King: Savoy type, matures in 80-85 days, cold tolerant
- Stonehead: Hybrid, matures in 70-75 days, disease resistant
For fall planting, choose varieties that mature in 80-100 days. They need time to develop before frost.
Harvesting Cabbage
Harvest cabbage when heads are firm and full-sized. Cut the head at the base with a sharp knife. Leave outer leaves in place if you want a second harvest.
Some varieties produce smaller side heads after the main head is cut. This is more common with loose-leaf types.
Harvest before temperatures drop below 20°F. Cabbage can handle light frosts, but hard freezes damage heads.
Store cabbage in the refrigerator for up to 2 weeks. For longer storage, keep in a cool, humid root cellar at 32°F to 40°F.
Common Mistakes When Planting Cabbage In Colorado
Many gardeners make these mistakes. Avoid them for a better harvest.
- Planting too late in spring: Heat causes bolting and bitter flavor
- Planting too early in fall: Hot soil and air stunt growth
- Overwatering: Leads to root rot and fungal diseases
- Underwatering: Causes tough leaves and small heads
- Skipping soil testing: Alkaline soil can block nutrient uptake
- Not hardening off transplants: Sudden exposure shocks plants
Learn from these errors. Your cabbage will thank you.
Frequently Asked Questions
Can I Plant Cabbage In Colorado In July?
Yes, for a fall harvest. Plant in late July to early August in lower elevations. Mountain areas should plant earlier in July.
What Is The Best Cabbage Variety For Colorado’s High Altitude?
Early Jersey Wakefield and Golden Acre are reliable. They mature quickly and handle cool nights well.
How Do I Protect Cabbage From Late Spring Frosts?
Use row covers, cloches, or old sheets. Water the soil before a frost to release heat overnight.
Should I Start Cabbage Seeds Indoors Or Direct Sow?
Starting indoors is safer for spring crops. Direct sowing works for fall crops or in warm microclimates.
How Often Should I Water Cabbage In Colorado?
Water deeply 1 to 2 times per week. Adjust based on rainfall and temperature. Mulch helps retain moisture.
Final Tips For Success
Timing is the most important factor for cabbage in Colorado. Start seeds early enough to avoid summer heat. For fall crops, plant late enough to avoid early heat but early enough for head formation.
Monitor your garden daily. Cabbage grows quickly once established. Check for pests and water needs regularly.
Keep a garden journal. Note planting dates, weather, and harvest results. This helps you refine your timing each year.
With the right timing and care, you can enjoy fresh, homegrown cabbage from your Colorado garden. Start planning now for your best harvest yet.