When to Plant Cabbage in Colorado (2026 Guide)

Cabbage is a versatile and nutritious addition to any garden in Colorado, thriving in the cool temperatures that this region often provides. With a frost-free season ranging from 133 to 174 days, depending on your USDA hardiness zone, it’s essential to understand when to start and harvest your plants. In cities like Aurora, the average last spring frost occurs around May 17, while in Boulder, it’s slightly earlier on May 5.

To achieve the best results, gardeners should carefully plan their planting schedule for cabbage. The vegetable is ideally suited for spring and fall harvests. By utilizing precise transplant and sowing windows based on established frost dates, gardeners can maximize their yield and enjoyment. For instance, in Grand Junction, the last spring frost falls as early as April 25, allowing for an earlier planting window compared to other parts of the state.

Growing cabbage in Colorado also presents unique challenges, such as late spring snowstorms or unexpected heat waves. Hence, knowing when to plant and how to care for your cabbage plants can significantly impact your success. With proper planning and techniques, such as crop rotation and soil amendments, you can enjoy this nutrient-rich vegetable throughout the growing season.

Planting Schedule by USDA Zone in Colorado

Zone	Indoor start	Transplant out	Direct sow	Harvest
Zone 5b	Start March 1 – March 15, ~6–8 weeks before May 5	Transplant outdoors between April 15 – May 5	Direct sow from May 10 – May 25	Harvest from July 15 – October 1
Zone 5a	Start March 5 – March 20, ~6–8 weeks before May 17	Transplant outdoors between April 25 – May 17	Direct sow from May 1 – May 20	Harvest from July 1 – September 27
Zone 6a	Start February 15 – March 1, ~6–8 weeks before April 25	Transplant outdoors between March 30 – April 25	Direct sow from May 1 – May 15	Harvest from June 30 – October 16

Cabbage Planting Windows in Colorado

Indoor start: For Zone 5b, start your cabbage indoors between March 1 and March 15.
Transplant outdoors: In Zone 5a, transplant your cabbage outdoors between April 25 and May 17.
Harvest: In Zone 6a, you can begin harvesting your cabbage around June 30 and continue until October 16.

Common Mistakes Growing Cabbage in Colorado

One common mistake is not realizing that late spring snow is a possibility in Colorado. Many gardeners are eager to plant their cabbage in early May, only to have their young plants damaged by frost. Always keep an eye on the extended forecast before transplanting seedlings.
Another mistake is overwatering. Colorado's dry climate can lead gardeners to think their soil is drier than it is, which can result in root rot. Always check the soil moisture before watering, as cabbage prefers consistent moisture without sitting in waterlogged conditions.
Failing to improve soil nutrients is a common oversight for cabbage growers in Colorado. A soil test can reveal deficiencies, and a lack of lime can exacerbate issues with clubroot disease, especially in acidic conditions. Enhancing the soil will ultimately lead to healthier plants.
Newer gardeners might underestimate how hot summer days can affect cabbage growth. If a heat dome moves in, the plant can bolt or stop growing effectively. Providing shade or harvesting early can help mitigate these issues for a successful crop.
Many gardeners assume cabbage doesn't need crop rotation, but this can be a critical misstep in Colorado gardens. Diseases like clubroot can build up in the soil, so rotating crops at least every three years helps prevent the buildup of pests and diseases.

Frequently Asked Questions

What if I'm in a cold pocket of Colorado?

It's essential to identify your specific frost dates to ensure successful cabbage growth. Planting later or using cloches can help shield seedlings from unexpected frosts. Consider waiting until early June to transplant for safety.

Can I still plant cabbage in May?

Yes, you can still plant cabbage in May, especially if you are in Zone 5b. However, watch the weather for any frost warnings, and consider direct sowing if you're concerned about transplant shock.

How long does it take for cabbage to mature?

Cabbage typically takes between 60 to 120 days to mature, depending on the variety. Smaller salad varieties can be ready sooner, while large storage cabbages may require the full growing season.

What pests should I watch for?

In Colorado, common pests include cabbage worms and aphids. Regularly inspect your plants and consider using organic traps or barriers to minimize their impact, promoting healthy cabbage growth.

Is crop rotation necessary for cabbage?

Yes, crop rotation is essential to prevent disease buildup in the soil. Avoid planting cabbage or any brassica family crops in the same area for at least three years to reduce the risk of clubroot and other soil-borne diseases.

Keep Learning

Typical fall sowing window for Cabbage in Colorado: July 6 – July 27.