🥦When to Plant Cauliflower in USDA Zone 6a (2026 Guide)
Fussier brassica that wants steady cool weather. Transplant early. Here is the cool-season planting schedule for cauliflower in zone 6a (covering areas like St. Louis MO, Philadelphia PA). All dates are based on 2026 frost data for your zone.
Start Seeds Indoors
Mar 9
Transplant
Apr 6
Harvest From
Jun 20
Because cauliflower is a cool-season crop, it tolerates light frost and can go out around Apr 6, before zone 6a's average last frost on Apr 20.
- Type: Cool-season
- Method: Transplant
- Days to harvest: 75
- Spacing: 18" apart
- Sun: Full sun
- Zone 6a frost: Apr 20 – Oct 15
- Season length: ~178 days
- Companions: beans, onion, celery
Growing cauliflower in zone 6a
Zone 6a has an average last spring frost around Apr 20 and a first fall frost around Oct 15, giving roughly 178 frost-free growing days. That window comfortably fits cauliflower's 75-day cycle, with room for a second succession planting if you time it right.
Get a head start by sowing seeds indoors around Mar 9, roughly 6 weeks before your last frost. Move the seedlings outside around Apr 6. Give each plant about 18 inches of space in full sun.
Zone 6a specific growing notes
In zone 6a (St. Louis MO, Philadelphia PA), your 178-day growing season means cauliflower should be one of your first spring plantings. Cool-season crops thrive in the mild part of your growing window. Monitor soil temperature — cauliflower germinates best when soil is 40-75°F.
Your first fall frost around Oct 15 means your last possible harvest is roughly late Oct. For a continuous supply, consider succession planting every 2-3 weeks from Apr 6 through mid-season.
Pro tip for cauliflower
Blanch heads by gathering outer leaves and tying them loosely over the developing curd with string or a rubber band when it reaches 2-3 inches across. This keeps the curd snowy white and prevents bitterness.
Troubleshooting cauliflower
Buttoning—forming tiny, unusable heads prematurely—is caused by temperature swings, drought stress, or root-bound seedlings. Transplant on time (not late), keep soil consistently moist, and choose stress-tolerant varieties.
Growing cauliflower in containers
One plant per 5-gallon pot, but cauliflower is the most challenging brassica for containers. It demands perfectly steady cool temperatures, no check in growth, and consistent moisture from transplant to harvest.
Can you plant cauliflower twice a year?
Yes—and fall cauliflower often outperforms spring-planted. Start seeds indoors in early July in zones 5+ and transplant by early August. Heads mature in September-October cooling weather with fewer pest issues.
Frequently asked questions
When should I plant cauliflower in zone 6a?
Transplant around Apr 6. If starting from seed indoors, sow around Mar 9. Because cauliflower is a cool-season crop, it tolerates light frost and can go out around Apr 6, before zone 6a's average last frost on Apr 20.
How long does cauliflower take to grow in zone 6a?
About 75 days from transplanting to first harvest. A Apr 6 planting in zone 6a is typically ready to pick from around Jun 20. Zone 6a has about 178 frost-free days — plenty of time for a second succession planting.
How far apart should I space cauliflower?
Space cauliflower about 18 inches apart in full sun. This gives each plant enough room for roots to spread and leaves to catch sunlight without competing.
What is the best tip for growing cauliflower?
Blanch heads by gathering outer leaves and tying them loosely over the developing curd with string or a rubber band when it reaches 2-3 inches across. This keeps the curd snowy white and prevents bitterness.
What are common problems with cauliflower and how do I fix them?
Buttoning—forming tiny, unusable heads prematurely—is caused by temperature swings, drought stress, or root-bound seedlings. Transplant on time (not late), keep soil consistently moist, and choose stress-tolerant varieties.
Can I grow cauliflower in a container?
One plant per 5-gallon pot, but cauliflower is the most challenging brassica for containers. It demands perfectly steady cool temperatures, no check in growth, and consistent moisture from transplant to harvest.
Can I plant a second crop of cauliflower for fall harvest?
Yes—and fall cauliflower often outperforms spring-planted. Start seeds indoors in early July in zones 5+ and transplant by early August. Heads mature in September-October cooling weather with fewer pest issues.
What grows well next to cauliflower?
Good companion plants for cauliflower are beans, onion, celery. Avoid planting near warm-season crops that compete for space and nutrients. Cauliflower also benefits from crop rotation — do not plant it in the same spot year after year.