When to Sow Outside: Not recommended. 1 to 2 weeks before your average last frost date, or 10 to 12 weeks before your average first fall frost date. In mild climates, sow in early fall for winter harvest.
When to Start Inside: RECOMMENDED. 4 to 6 weeks before transplanting outside after your average last frost date, or 12 weeks before your average first fall frost date. In mild climates, sow in fall for harvest in late winter and early spring. Ideal soil temperature for germination is 70°-85°F, cooler (60°F) growing temperatures thereafter.
How many do I plant?: Each plant produces one cauliflower head, but if all plants are started at once they will be ready close to the same time. This is beneficial if you plan to freeze or pickle it.
Use a lightweight, seed-starting mix/medium (sterile, and lighter than potting mix), and sow seeds ¼" deep. Sow 2-3 seeds per pot, thinning to the strongest plant once leaves appear (clip extra plants at the soil level using scissors). The strongest plant may not be the tallest; look for thick, strong stems and deep color. By thinning early, you minimize the negative impact of crowding, like stretching for light. Read more indoor sowing tips.
Containers should be clean, sanitized, and have drainage holes. If you choose to sow in cell packs, you may need to up-pot seedlings once into larger containers before transplanting outside
After hardening off, transplant seedlings 24" apart
Sowing preparation and spacing
Sow a group of 3 seeds every 24".
Cauliflower is a cool-season crop, tolerating a light frost. It is best sown in the summer for fall harvest, because the heads need to mature in cool weather; plants produce best when temperatures are in the 60°-65°F range. If your spring season is long and cool, cauliflower will also do very well when sown in early spring.
When seedlings are 2" tall thin to 1 every 24".
Keep soil consistently moist.
If soil is deficient, amend with a slow-release, balanced (equal parts nitrogen, phosphorus, and potassium) fertilizer prior to transplanting, or use a balanced, liquid fertilizer regularly.
Keep plants well weeded. Weeds compete with crops for light, nutrients, and water, and can harbor insects and diseases.
Covering plants with row cover at transplant can help to prevent common pests like cabbage moths and aphids. Since plants do no not need pollination (the head is composed of unopened flowers) they can remain covered until harvest. If small plants are stressed by temperatures that are too hot or too cold, heads begin to form prematurely (called "buttoning") and heads will be small. Buttoning can also happen when plants are stunted because seedlings were kept in a growing container too long, are grown in poor soil, or exposed to drought. Avoid stressing plants for best results. To ensure white rather than off-white or yellow heads, you can gently tie up the leaves or bend a few leaves, breaking the mid-rib, and tuck them across the head for sun protection (blanching).
Harvest heads in the morning, if possible, and when buds are tight. Cut stalk below the head. Dunk heads in ice water to reduce any "field heat" and increase storage time. Allow to drain before storing.
FRESH: Store dry heads in a sealed container in the refrigerator vegetable drawer for up to 2 weeks. FROZEN: Blanch by dropping in boiling, salty water for about 3 minutes. Plunge into ice water to stop cooking. Once cooled, place in an airtight, freezer-safe container.