Growing Onions from Seed: A Step-by-Step Guide for Success

Growing onions from seed is a rewarding and economical way to cultivate fresh, flavorful onions. While it requires a bit more patience than planting onion sets, starting from seed allows you to choose from a wider variety of onions, including unique heirlooms and specialty types. With proper care and attention, you can enjoy a bountiful harvest of homegrown onions.

This guide covers everything you need to know about growing onions from seed, including sowing, transplanting, and harvesting.

Table of Contents

1. Why Grow Onions from Seed?
2. Choosing the Right Onion Seeds
3. When to Plant Onion Seeds
4. How to Grow Onions from Seed
   • Sowing Indoors
   • Sowing Directly Outdoors
5. Caring for Onion Seedlings
6. Transplanting Onion Seedlings
7. Harvesting Onions Grown from Seed
8. Common Problems When Growing Onions from Seed
9. FAQs About Growing Onions from Seed
10. Conclusion
11. Meta Description

Why Grow Onions from Seed?

Starting onions from seed offers several advantages:

• Wider Variety: Access to unique and heirloom varieties not available as sets.
• Better Storage: Onions grown from seed often store longer than those grown from sets.
• Cost-Effective: Seeds are more affordable than onion sets.
• Healthier Plants: Seeds are less likely to carry diseases compared to sets.

Choosing the Right Onion Seeds

Select onion seeds based on your climate, taste preferences, and intended use:

• Short-Day Onions: Best for warmer climates; require fewer daylight hours.
• Long-Day Onions: Ideal for cooler climates with longer summer days.
• Intermediate-Day Onions: Suitable for temperate regions.
• Popular Varieties:
  • Ailsa Craig: Large, mild-flavored onions.
  • Red Baron: Vibrant red onions with a sweet taste.
  • Sturon: Reliable, long-storing onions.

When to Plant Onion Seeds

1. Indoors:
   • Sow seeds indoors 8-10 weeks before the last frost date.
   • Ideal for long-day and intermediate-day onions.
2. Outdoors:
   • Direct sow in late winter or early spring when the soil is workable.

How to Grow Onions from Seed

Sowing Indoors

1. Prepare Seed Trays:
   • Fill seed trays or pots with seed-starting compost.
2. Sow Seeds:
   • Plant seeds ¼ inch deep, spacing them about ½ inch apart.
3. Water Gently:
   • Moisten the soil with a fine spray of water.
4. Provide Light:
   • Place trays in a sunny windowsill or under grow lights.
5. Temperature:
   • Maintain a temperature of 18°C-21°C (65°F-70°F) for germination.

Sowing Directly Outdoors

1. Prepare the Soil:
   • Choose well-draining, fertile soil. Work in compost or organic matter.
2. Mark Rows:
   • Space rows 12-18 inches apart.
3. Sow Seeds:
   • Plant seeds ¼ inch deep and 1 inch apart.
4. Water:
   • Keep the soil evenly moist until seeds germinate.

Caring for Onion Seedlings

1. Thinning:
   • Once seedlings are 2-3 inches tall, thin them to 2-3 inches apart.
2. Watering:
   • Water regularly to keep the soil consistently moist.
3. Fertilizing:
   • Apply a nitrogen-rich fertilizer every 2-3 weeks to promote healthy growth.
4. Weeding:
   • Keep the area weed-free to prevent competition for nutrients.

Transplanting Onion Seedlings

1. When to Transplant:
   • Transplant seedlings outdoors when they are 4-6 inches tall and after the last frost.
2. Prepare the Bed:
   • Loosen the soil and amend with compost.
3. Planting Depth:
   • Place seedlings so the roots are covered, and the neck is just above the soil surface.
4. Spacing:
   • Space onions 4-6 inches apart in rows 12-18 inches apart.
5. Watering:
   • Water immediately after transplanting to settle the soil.

Harvesting Onions Grown from Seed

1. When to Harvest:
   • Onions are ready to harvest when the tops turn yellow and fall over.
2. How to Harvest:
   • Use a garden fork to gently lift onions from the soil.
3. Curing:
   • Dry onions in a warm, airy place for 2-3 weeks before storing.
4. Storage:
   • Store in a cool, dry location with good ventilation.

Common Problems When Growing Onions from Seed

1. Poor Germination:
   • Cause: Old seeds or incorrect planting depth.
   • Solution: Use fresh seeds and sow at the correct depth.
2. Bolting:
   • Cause: Temperature fluctuations.
   • Solution: Plant at the right time and use bolt-resistant varieties.
3. Pests:
   • Onion Flies: Cover plants with insect netting.
   • Aphids: Spray with soapy water or neem oil.

FAQs About Growing Onions from Seed

1. How long do onions take to grow from seed?
   • Onions take 4-5 months from seed to harvest.
2. Can I start onion seeds outdoors?
   • Yes, in early spring when the soil is workable.
3. Do onion seeds need soaking before planting?
   • Soaking is optional but can speed up germination.
4. How many onions grow from one seed?
   • Each seed produces a single onion bulb.
5. Can I save onion seeds from year to year?
   • Yes, store seeds in a cool, dry place, but germination rates decline after a year.
6. Do onions grown from seed store well?
   • Yes, they often store better than onions grown from sets.
7. Can I grow onions indoors year-round?
   • Spring onions can be grown indoors, but bulb onions need outdoor conditions.
8. How deep should I plant onion seeds?
   • Sow seeds ¼ inch deep.
9. Do onions need fertilizer?
   • Yes, onions benefit from a nitrogen-rich fertilizer during growth.
10. What’s the best soil for onions?
    • Well-draining, fertile soil with a pH of 6.0-7.0.

Conclusion

Growing onions from seed is an excellent way to enjoy a wide variety of fresh, flavorful onions while saving money and enhancing your gardening skills. By following the proper steps for sowing, caring for seedlings, and transplanting, you can achieve a successful harvest. With patience and care, your efforts will be rewarded with a bounty of homegrown onions.