When to start cauliflower seeds
Short answer: sow cauliflower indoors 4 to 6 weeks before transplanting, and transplant about 2 weeks before your average last frost. It is fussier than broccoli or cabbage, so variety choice and timing matter.
At a glance
- Start indoors
- 4–6 weeks before setting out (UNH; Iowa State)
- Set out
- About 2 weeks before last frost (UNH)
- Germination temperature
- 65–70°F (Iowa State); no bottom heat (UMN)
- Days to sprout
- 4–7 days (Iowa State); 10 days at 59°F soil, 5 days at 77°F (Harrington)
- Direct sow?
- Yes, for fall crops (UMN direct seeds in July in Minnesota)
UNH = University of New Hampshire Extension; UMN = University of Minnesota Extension; Harrington = J. F. Harrington's germination data as published by Oregon State University Extension. Full links are under Sources below.
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How many weeks before the last frost?
University of New Hampshire Extension gives cauliflower 4 to 6 weeks from seed to transplant and says it is safe to set out 2 weeks before the last frost. That is later than cabbage (4 weeks before), so treat cauliflower as the more cautious of the two. With an average last frost of May 10, you would sow indoors March 15 to March 29 and set plants out April 26.
Pick a spring-friendly variety
University of Minnesota Extension recommends heat-tolerant varieties with a short growth cycle (50 to 60 days to harvest) for spring planting, and names 'Snow Crown' as one of the best for spring. Long-season types are better saved for fall, when heads mature in cool weather.
Germination
Harrington's data (published by Oregon State Extension) list a 40°F minimum and 80°F optimum soil temperature, with emergence in about 19 days at 50°F, 10 days at 59°F, 6 days at 68°F and 5 days at 77°F. Iowa State Extension lists 65–70°F with seedlings in 4 to 7 days.
Press seed a quarter to a half inch deep in sterile seedling mix. As with broccoli, UMN says not to use bottom heat; expect seedlings in about two weeks at ordinary room temperatures, and turn on bright lights as soon as they appear.
Growing on, hardening off and transplanting
Feed with a half-strength starter solution once a week from the first true leaf, then twice a week after two true leaves (UMN). At four or five true leaves, after about four weeks, begin hardening off: reduce watering, give plants a sheltered spot with a couple of hours of sun, and increase sun and wind over the next week while keeping them watered.
UMN spaces cauliflower 18 inches apart, set at the same depth as in the pot, and suggests a row cover for the first weeks. In spring, use a heavier cover that protects against cold; in summer, a lightweight one so plants don't overheat.
Fall cauliflower and direct sowing
UMN starts fall cauliflower in early to late July, indoors or by direct seeding. When direct sowing, drop three seeds every 18 inches, a quarter to a half inch deep, and thin to one. Water through hot spells. The fall planting calculator gives the latest date for your variety's days to maturity.
Common mistakes
- Long-season varieties in spring. They can run into summer heat before heading.
- Transplanting too early. Cauliflower goes out later than cabbage: about 2 weeks before last frost, not 4.
- Warm, leggy seedlings. Skip the heat mat after germination.
- Stressing young plants. Heat, drought and insects are hardest on small plants; water and cover them.
Example schedules
The same timing rules applied to three different average last frost dates. Find your own date on the frost dates page, or check your zone planting calendar for typical ranges.
| Last frost | Start indoors | Plant out | Direct sow |
|---|---|---|---|
| Mar 15 | Jan 18–Feb 1 | Mar 1 | — |
| Apr 15 | Feb 18–Mar 4 | Apr 1 | — |
| May 15 | Mar 20–Apr 3 | May 1 | — |
Supplies
Optional. You can start seeds with very little gear; these are the items that make the steps above easier. Disclosure: some links on this site may be affiliate links; if you buy through them we may earn a commission at no extra cost to you. Learn more.
- Row cover (frost-weight for spring, lightweight for summer): UMN suggests matching cover weight to the season.
- Short-season cauliflower seed: 50–60 day varieties suit spring planting.
- Seed-starting mix and cell trays: 4–6 weeks indoors.
Frequently asked questions
When should I plant cauliflower transplants outside?
About 2 weeks before your average last frost (UNH), after hardening off.
What cauliflower variety is best for spring?
UMN recommends heat-tolerant, short-cycle varieties (50–60 days to harvest), naming 'Snow Crown' as one of the best for spring.
How long do cauliflower seeds take to germinate?
Iowa State says 4–7 days at 65–70°F. Harrington's data show about 10 days at 59°F and 5 days at 77°F soil.
Sources
- University of New Hampshire Extension — Growing Vegetables: When to Plant Your Vegetable Garden
- Oregon State University Extension — Soil temperature conditions for vegetable seed germination (J. F. Harrington data)
- Iowa State University Extension — Germination Requirements for Annuals and Vegetables
- University of Minnesota Extension — Growing cauliflower in home gardens
- University of Minnesota Extension — Starting seeds indoors
Dates in the calculator and example tables use the University of New Hampshire Extension timings. Average frost dates are not guarantees; check the forecast before setting out tender plants. Last reviewed 2026-10-23. Found an error? Tell us.