I recently got an email from an Epic Gardening reader with a familiar question. When I first started gardening and didn’t know how to start seeds, I had the same question:
Sally, that’s a great question! Knowing the answer will help you learn more about gardening and starting seeds in general, because it depends on an important idea: germination rates.
Cauliflower is a delicious and nutritious vegetable that is enjoyed by many. However, getting a good harvest from your cauliflower plants requires proper planting techniques. One key question is how many cauliflower seeds to plant per hole or cell when starting the plants. This article will provide a complete guide to planting cauliflower seeds successfully.
When to Plant Cauliflower Seeds
Cauliflower is a cool weather crop that takes around 2-4 months to reach maturity This means seeds should be started based on your target harvest period
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For spring harvest, direct sow seeds in late winter or start indoors 6-8 weeks before last frost date.
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For fall harvest, direct sow in mid to late summer or start indoors in early summer.
Many gardeners prefer starting cauliflower indoors as it gives more control over conditions and avoids pest damage
How to Start Cauliflower Seeds Indoors
When starting cauliflower seeds indoors, use seed starting mix and containers with proper drainage. Follow these steps:
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Fill containers with moistened seed starting mix.
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Plant seeds 1/4-1/2 inch deep, spacing 2-3 seeds per cell or compartment.
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Maintain soil moisture and provide plenty of light.
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Thin to 1 plant per cell once seedlings emerge.
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Harden off plants for 7-10 days before transplanting outdoors.
Timing for Indoor Seed Starting
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For spring harvest, start seeds indoors 6-8 weeks before your last expected frost date.
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For fall harvest, start seeds 12-14 weeks before your first expected fall frost.
This timing allows plants to grow large enough for transplanting on schedule.
Direct Sowing Cauliflower Seeds Outdoors
Many gardeners, especially those with short growing seasons, prefer to direct sow cauliflower seeds into the garden. Follow these tips:
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Prepare soil by mixing in several inches of compost or other organic matter. Cauliflower needs nutrient-rich soil.
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Wait until soil has warmed to at least 45°F before sowing.
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Plant seeds 1/4-1/2 inch deep and 12-18 inches apart in rows spaced 30-36 inches apart.
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Drop 2-3 seeds per planting hole and thin later.
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Keep soil consistently moist for proper germination.
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Thin seedlings to 1 plant per hole after emergence.
Timing for Direct Sowing
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For spring harvest, direct sow 2-4 weeks before your last expected frost date.
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For fall harvest, sow in mid to late summer based on days to maturity for the variety planted.
How Many Seeds Per Hole When Planting Cauliflower?
The recommended number of cauliflower seeds to plant per hole is 2-3 seeds. Here’s why:
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Planting multiple seeds improves germination rates in case one fails.
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Extra seeds allow you to select and retain the strongest seedling after thinning.
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Spacing seeds 2-3 inches apart reduces root disturbance when thinning later.
Thin down to 1 plant per hole 2-3 weeks after emergence.
Follow Proper Thinning and Spacing
Proper thinning and spacing of cauliflower is critical:
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After seeds germinate, thin down to 1 plant every 12-18 inches.
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Space rows 30-36 inches apart.
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Avoid overcrowding, which causes smaller heads.
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Thin gradually over 2-3 weeks to reduce transplant shock.
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Water plants well after thinning to help recovery.
Provide Consistent Moisture
Cauliflower requires consistent soil moisture throughout its growth:
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Water transplants frequently after planting.
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Use mulch to conserve moisture once plants establish.
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Provide 1-2 inches of water per week if rain is lacking.
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Avoid water stress, which causes poor growth and loose, ricey curds.
Control Pests and Diseases
Cauliflower can be susceptible to certain pests and diseases:
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Cabbage worms – Use BT spray or row covers
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Clubroot – Rotate planting areas to prevent this fungal disease
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Downy mildew – Improve air circulation and avoid wet foliage
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Cutworms – Use cardboard collars around seedlings
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Aphids – Blast off with water, use insecticidal soap
Harvest at Proper Maturity
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Check heads frequently as they mature and harvest immediately when tight and firm.
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Cut heads with 4-6 inches of stem attached.
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Store at 32-40°F with high humidity for 2-4 weeks.
Get a Jump Start for Next Year
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At end of season, save some seed to start indoors next year.
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Clean and store seeds in a cool, dry place over winter.
Answer Two: Seedling Selection
Just as not all seeds are created equal from a germination standpoint, not all seeds germinate equally. Sometimes you have a seed that shoots off like a rocket and becomes too leggy. If this was the only seed in your insert, you’d be forced to use it.
You can pick the seedlings that look the strongest by planting two to three seeds in each cell. You just need to pick the one you like best and cut off the other seedlings to kill them while the ones you chose grow.
Answer One: Seed Germination Rates
Not all seeds are created equal. Some plant species have higher germination rates than others. Some seeds from the same type of plant are older than others, which slows down the rate at which they sprout.
Imagine you’re growing arugula microgreens and the average germination rate is 90%. Just 65 of the 72 plant inserts in a 72-plant starter tray will actually sprout if you plant one arugula seed in each one.
Now imagine you plant multiple seeds at three arugula seeds per insert. Every one of these seeds has a 10% chance of failing, which means the chance of all of them failing is only 20%. 1%. This means that you are 99. 9% likely to have the seeds in that cell germinate. So, in a tray with 72 inserts, it’s very unlikely that any seeds would not germinate, unless there are other things that stop seeds from germinating.
In short: Plant multiple seeds per hole to increase the chances you have perfect germination rates.
How I Grow Giant Cauliflower From Seed To Harvest – Step-By-Step Cauliflower Guide
FAQ
How many seeds to put in each hole?
How many cauliflower heads do you get from one plant?
What is the secret to growing cauliflower?
Should cauliflower seeds be soaked before planting?
How many cauliflower seeds should I plant?
When starting indoors, sow 2 to 3 cauliflower seeds up to 1/2 an inch deep in small nursery pots or seed starting trays/flats. Keep potting soil evenly moist but not soggy, which could cause seeds or seedlings to rot. If multiple seeds germinate, thin to 1 cauliflower seed per pot/cell.
How far apart do you plant cauliflower?
If multiple seeds germinate, thin to 1 cauliflower seed per pot/cell. If directly sowing outdoors, again sow 1/2 an inch deep, 2 to 3 cauliflower seeds (more if your seeds are old) at least 18 inches apart or more. To transplant cauliflower seedlings, space them 18 inches or more apart in well-draining, rich soil.
How deep do you plant cauliflower seeds?
Cauliflower seeds germinate best when sown indoors, planted 1/2 inch (1.25 cm) deep, and preferably at least 2 to 3 seeds per planting hole and thinning out to one sprout after. You can sow cauliflower directly outdoors (under row covers or plastic), but for best success, you should start your cauliflower seeds indoors and transplant later.
How many seedlings should a plant have per hole?
All you have to do is determine which one you like the most, then snip off the other seedlings to kill them as your other plants grow. The number of germs per cell will vary based on the species. Like most things in gardening, there are always exceptions to this rule of 2-3 seeds per hole.
How many cucumber seeds should I plant per hole?
When planting cucumber seeds, it’s recommended to only plant 1 seed per hole. Due to the size of the seeds, overlapping with multiple seeds can hinder germination. You can plant each seed closer together though.
How much water do you need to grow cauliflower?
Sow three or four cauliflower seeds one half-inch deep every 18 inches in row. Space rows two to three feet apart. Once the plants are established, thin them to one plant for every 18 inches of the row. Consistent moisture will produce a solid head. Plants should receive an inch of water each week.