Cauliflower (Brassica oleracea var. botrytis) is the same species as broccoli, cabbage, Brussels sprouts and turnip, and has many similar needs for good garden performance. For the best quality cauliflower, grow it in rich, moist soil without drought stress.
For those who love it, nothing is better than the richness of cauliflower in an Indian curry, a North African stew, or a creamy soup. In many Minnesota kitchens, raw on a vegetable platter, steamed as a side dish, baked in a cheesy casserole, or pickled and served with a sandwich are all common recipes.
The dense, mounded head of cauliflower is the “curd.” The curd is the flowering stalk of the plant. The edible stage is before the flowers open. Dense, flavorful curds grow in cool temperatures, between 50°F and 70°F.
Some varieties are good for spring planting, growing quickly and producing curds before hot summer weather sets in. Most types are best as a mid-summer planting for fall harvest.
Warm weather during growth of the leafy portion of the plant helps build a large plant, leading to a larger head. Pointy, green Romanesco cauliflower is a fall crop.
Gardeners in the far northeastern part of Minnesota, from Duluth north, can grow excellent quality cauliflower all summer long.
Cauliflower is a cool-season vegetable that can be tricky to grow successfully. Unlike hardier crops like cabbage and broccoli, cauliflower is very particular about temperatures – too cold or too hot, and you’ll end up with small, stunted heads or no heads at all. The key is starting cauliflower seeds at just the right time indoors, before transplanting seedlings outside according to your local climate. Follow this guide for tips on ideal timing and techniques for starting cauliflower seeds indoors.
Why Start Cauliflower Indoors?
Growing cauliflower from seedlings started inside has several advantages compared to direct-sowing seeds into the garden
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You can get plants growing 4-6 weeks before outdoor planting This head start is crucial for cauliflower
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Indoor conditions are ideal for uniform germination. Seeds sprout quickly and evenly.
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Seedlings are protected from cold, pests, diseases, and bad weather while small.
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You can grow heirloom or specialty varieties not found as transplants.
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It costs much less than buying nursery transplants.
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Starting seeds spreads tasks out over several weeks.
If cauliflower has failed you in the past, starting seeds indoors makes the process more controlled and sets up seedlings for success after transplanting.
When to Sow Cauliflower Seeds Indoors
Timing is critical when starting cauliflower seeds indoors. Here are some general guidelines:
For Spring Harvest
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Start seeds indoors 4-6 weeks before your last average spring frost date.
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In warmer climates, start closer to 4 weeks before. In cooler areas, go with 6 weeks.
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Transplant seedlings outdoors 2-4 weeks before the anticipated last frost.
For Fall Harvest
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Start seeds indoors 6-8 weeks before your first average fall frost date.
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Transplant seedlings into the garden 4-6 weeks before the first fall frost.
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For late fall harvest, sow 8-10 weeks before frost and transplant 6-8 weeks before.
Always check local frost dates and weather forecasts – cold snaps or heat waves will affect timing. Choose bolt-resistant varieties if hot weather follows spring crops.
How to Start Cauliflower Seeds Indoors
Follow these steps for success with starting cauliflower seeds indoors:
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Choose containers at least 2-3 inches deep with drainage holes. Use seed trays, peat pots, or recycled containers.
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Use a seed starting mix. Sterile, soilless mixes prevent damping off disease. They are lightweight and retain moisture well.
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Plant the seeds. Fill containers with moistened mix. Sow seeds 1⁄4-1⁄2 inch deep, spaced 1-2 inches apart.
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Provide warmth. Cauliflower seeds germinate best around 70°F. Use heating mats or grow lights to maintain temperature.
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Give light immediately after sprouting. Place under grow lights or a sunny window. Keep lights 2-4 inches above seedlings.
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Gradually acclimate and transplant. Harden off seedlings by slowly increasing outdoor time over 7-14 days before transplanting into garden beds.
Follow these steps for healthy, vigorous cauliflower seedlings ready to grow quickly after transplanting. Just be diligent about timing for your desired harvest period.
Tips for Robust Seedlings
Here are some additional tips for success:
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Water carefully to keep soil consistently moist but not soggy.
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Turn containers frequently for even, straight seedling growth.
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Thin overcrowded seedlings, leaving the strongest 1-2 inches apart when true leaves appear.
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Use small fans to increase air circulation and prevent fungal issues.
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Stop fertilizing 2 weeks before hardening off to avoid transplant shock.
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Let soil dry slightly between waterings as seedlings acclimate outside.
When to Transplant Outdoors
Time transplanting seedlings into the garden based on plant size and soil temperatures:
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In early spring, transplant when seedlings reach 4-6 inches tall and soil is at least 50°F.
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For fall crops, transplant when summer heat passes and soil drops back down to 60-70°F.
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Avoid transplanting during temperature swings at either extreme. Cauliflower needs steady, cool conditions.
Benefits of Starting Cauliflower Indoors
The controlled process of starting seeds inside offers many advantages:
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Extends harvest with earlier maturity.
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Avoids transplant shock that direct-sown seeds face.
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Reduces pest, disease, and weed pressure.
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Conserves garden space in early spring.
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Provides flexibility if weather turns cold or hot.
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Allows monitoring and care of individual seedlings.
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Enables growing heirloom and specialty varieties.
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Requires minimal supplies and saves money over buying transplants.
With proper timing, gentle handling, and protection from temperature fluctuations after transplanting, cauliflower seedlings started indoors will reward you with vigorous growth and bountiful harvests. Don’t be intimidated – just follow the steps and you’ll succeed with cauliflower from seed!
Growing Cauliflower from Seeds
Transplant your seedlings outside two to four weeks before the last frost date. They’ll still be sensitive to cold, so make sure to harden them off carefully first. Set them outside, out of the wind, for about one hour, then bring them inside. Repeat this every day, leaving them outside an hour longer each time. If it’s unusually cold out, skip a day. Keep this up for two weeks before planting them in the ground.
Soil pH and fertility
- Have your soil tested.
- Grow cauliflower in well-drained yet moisture-retentive, fertile soil with pH of 6 to 7. A good cauliflower crop needs this ideal garden soil.
- Apply phosphorus (P) and potassium (K) according to soil test recommendations.
- Many Minnesota soils have enough phosphorus. Unless your soil test report specifically recommends additional phosphorus, use a low- or no-phosphorus fertilizer.
- It is not worth growing cauliflower unless the plants absorb water and nutrients steadily during their growth.
- Improve your soil by adding well-rotted manure or compost in spring or fall.
- Do not use fresh manure as it may contain harmful bacteria and increase weed problems.
- If you use manure or compost, you may not need more fertilizer applications, depending on how much organic matter you use.
- Side-dress when the plants are about four inches tall.
- Do not use any fertilizer containing a weed killer (“Weed and Feed”), as it may kill your vegetable plants.
For spring-planted cauliflower, it is best to plant in early to mid- April. Choose a variety with heat tolerance and a short growth cycle (50 to 60 days to harvest). ‘Snow Crown’ is one of the best for spring growth.
For the fall crop, start seeds indoors or direct seed in the garden, in early to late July.
Whether you plant in spring or summer, a row cover will protect the plants from wind and insects during the first weeks of growth. In spring, use a cover material that will give protection against cold. In summer, use a lightweight material so that temperatures do not get too hot under the cover.
If strong winds loosen a floating row cover, it can do more damage than the plants would suffer without it. Be sure to anchor it firmly with soil and/or pins at the edges. Alternatively, support the row cover with wire hoops, forming a low tunnel.
- Use sterile soilless seedling mix and press the seeds one-fourth to one-half inch deep.
- Do not use bottom heat. The seeds will germinate and the plants will grow well in summer temperatures.
- Seeds should germinate in about two weeks. Turn on bright grow lights above them once the seedlings emerge.
- Apply fertilizer to developing seedlings beginning when the first true leaf appears. Use a half-strength starter solution once a week. After two true leaves are present, apply fertilizer twice a week.
- When the plants have four or five true leaves, after about four weeks, begin hardening them off so that they will adapt well when transplanted outdoors. Reduce watering. Place plants outside where they will receive wind protection and a couple hours of sunlight.
- Gradually expose them to more sunlight and wind over the next week. Keep them well watered.
- Dig small holes with a trowel, or dig a narrow trench with a shovel. Place the seedlings 18 inches apart. Fill the soil around them so that the plant is at the same level it was in its pot.
- Water the plants in, or use a liquid starter solution high in phosphorus and low in nitrogen and potassium.
- Apply a row cover, if using.
- Direct seed cauliflower in July.
- Plant seed shallowly, one fourth to one-half inch deep, dropping three seeds every 18 inches.
- Keep the soil moist during seedling emergence.
- Once the plants emerge, thin so that one seedling remains every 18 inches.
- Take care of the seedlings. When small, they experience extreme heat, wind, drought, and insects. Water them as needed.
The Complete Guide to Growing Cauliflower
FAQ
Should cauliflower seeds be started indoors?
Cauliflower While cauliflower can be direct seeded in the garden, most folks choose to start their seed indoors about six weeks before setting the plants into the garden after the last frosts have passed. Cauliflower will not do well if planted inside sooner as the plants get root-bound and large.
How long does cauliflower take to grow from seed?
How big should cauliflower seedlings be before transplanting?
Transplant young cauliflower seedlings when they have two sets of leaves or more and are about 10 to 15cm in height. This is around six weeks after sowing. Plant the seedlings out 60cm apart, in rows 60cm apart. When planting a good rule of thumb is to plant them at the depth they were in the punnet.
What should you not plant next to cauliflower?
| Vegetable | Bad Companion Plants |
|---|---|
| Brussel Sprouts | Mustards, nightshades |
| Cabbage | Grapes |
| Carrots | Dill, parsnip and radish |
| Cauliflower | Dill, parsnip and radishes |
How do you start cauliflower seeds indoors?
Follow these steps for the best results starting cauliflower seeds indoors: Select containers at least 2-3 inches deep with drainage holes. Options include seed trays, peat pots or recycled containers. Use a sterile, soilless mix to prevent damping off disease. Mixes for seed starting are lightweight and retain moisture.
Can you grow cauliflower indoors?
Some popular varieties for indoor cultivation include ‘Snow Crown,’ ‘Self-Blanche,’ and ‘Amazing.’ Start early: Cauliflower takes a long time to mature, so it’s important to start them indoors early. Start your cauliflower seeds indoors about 6-8 weeks before the last expected frost date in your area.
When should I plant cauliflower seeds?
Cauliflower is a cool-season crop. Cauliflower thrives in temperatures between 57°F and 68°F (14°C-20°C). Set cauliflower seedlings in the garden about two or three weeks before the average last frost date, not earlier. Sow cauliflower seeds indoors 4 to 6 weeks before setting seedlings in the garden.
How do you grow cauliflower?
Here’s some great tips on ways to grow cauliflower: Note: Transplants work best but can be direct seeded. (See below.) Fall planting (for a winter crop): Start seeds indoors 4 to 6 weeks prior to your planned planting date. In areas where temperatures tend to stay above 32 degrees, a winter crop can be transplanted from September to February.
What are the problems when starting cauliflower seeds indoors?
Here are some potential issues and how to address them when starting cauliflower seeds indoors: Leggy seedlings – Insufficient light, move closer to lights Damping off disease – Soil too wet, allow to dry between waterings Slow growth – Too cold, increase temperature Purple leaves – Phosphorus deficiency, amend soil
How long does cauliflower take to grow?
Plant fast-maturing cauliflower varieties in spring or fall. Any variety that requires more than 80 days to mature should be planted for fall harvest. Purple varieties are both heat and cold-tolerant. Cauliflower matures in 50 to 85 days depending on the variety. Start cauliflower from seed or transplants. Seed is viable for 4 years.