It can be hard to grow cauliflower because it grows best in cool weather. While cabbage and broccoli can handle a wide range of temperatures, cauliflower is very picky about its own. If it’s too cold or too hot, it will grow small, stunted heads or none at all. It’s important to start cauliflower seeds indoors at the right time for your area’s weather before moving the seedlings outside. How to start cauliflower seeds indoors and the best time to do it are explained in this guide.
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.
Starting seeds indoors makes the process more manageable and helps seedlings do well after being moved outside if cauliflower has failed you in the past.
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.
Check the local frost dates and weather forecasts every time. Heat waves or cold snaps can change the dates. 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.
- Cauliflower should be grown in fertile soil that drains well but holds on to water and has a pH of 6 to 7. A good cauliflower crop needs this ideal garden soil. Use potassium (K) and phosphorus (P) as directed by the soil test. Many Minnesota soils have enough phosphorus. Use a low- or no-phosphorus fertilizer unless your soil test report says that you need to add more phosphorus.
- Cauliflower shouldn’t be grown unless the plants steadily take in water and food as they grow.
- If you want to make your soil better, add compost or well-rotted manure in the spring or fall.
- Do not use fresh manure because it could have bacteria that are bad for you and make weed problems worse.
- If you use a lot of organic matter, like manure or compost, you might not need to use as much fertilizer.
- Side-dress when the plants are about four inches tall.
- If the fertilizer you use has a weed killer in it (like “Weed and Feed”), it could 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.
A floating row cover can hurt plants more than they would without it if strong winds blow it off. 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.
- Do not use soilless seedling mix, and bury the seeds 1/4 to 1/2 inch deep.
- Do not use bottom heat. The seeds will sprout, and the plants will do well in the hot summer weather.
- Seeds should germinate in about two weeks. Once the seedlings come up, put bright grow lights over them.
- When the first true leaf appears, you can start fertilizing seedlings that are growing. Use a half-strength starter solution once a week. Once there are two true leaves, fertilize the plant twice a week.
- Start hardening off the plants when they have four or five true leaves, which should be after about four weeks. This will help them do well when they are moved outside. Reduce watering. Place plants outside where they can get some sun and protection from the wind.
- Over the next week, slowly expose them to more wind and sun. Keep them well watered.
- Use a trowel to make small holes or a shovel to make a narrow trench. Place the seedlings 18 inches apart. Put enough soil around them to keep the plant at the same height it was in the pot.
- You can water the plants or use a starter liquid that is high in phosphorus and low in nitrogen and potassium.
- Apply a row cover, if using.
- Direct seed cauliflower in July.
- Plant seeds only a quarter to half an inch deep and drop three seeds every 18 inches.
- Keep the soil moist during seedling emergence.
- When the plants come up, thin them so that there is one seedling left 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: Cauliflower seeds can be planted directly in the garden, but most people choose to start their seeds indoors about six weeks before putting the plants in the garden after the last frost. 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 you plant them, it’s a good idea to put them at the same 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?
To start cauliflower seeds indoors successfully, do these things: Choose pots that are at least 2 to 3 inches deep and have holes in them for drainage; 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.