Growing Onions: A Complete Beginner's Guide

Introduction to Growing Onions

Onions (Allium cepa) are one of humanity's oldest cultivated crops, grown for over 5,000 years since their domestication in Central Asia. Today, they're an essential ingredient in cuisines worldwide and one of the most rewarding vegetables for home gardeners.

What makes onions special is their incredible versatility. You can harvest them young as scallions, enjoy them fresh as sweet onions, or cure them for months of storage. With the right variety selection for your region, you'll enjoy a bountiful harvest.

Why Grow Your Own Onions?

Freshness and Flavor

Homegrown onions have a depth of flavor that store-bought can't match. You can harvest them at the perfect stage—mild and sweet when young, or pungent and complex when fully mature.

Cost Savings

A single packet of onion seeds or a bag of sets produces dozens of bulbs. Once you master storage techniques, you'll have onions year-round.

Variety Selection

Commercial growers focus on a few varieties that ship well. Home gardeners can grow specialty types like Cipollini, Walla Walla Sweets, or heirloom red varieties.

Storage Potential

Properly cured storage onions keep for 6-8 months, providing homegrown flavor through winter and early spring.

Understanding Onion Types

By Color

By Day-Length Requirement

This is the most important factor for successful onion growing:

Pro Tip: Choose the wrong day-length type and your onions won't bulb properly! Check your latitude and choose accordingly.

What You'll Need

Essential Supplies

• Onion seeds, sets, or transplants
• Garden bed or containers (at least 6 inches deep)
• Balanced fertilizer (10-10-10 or 10-20-10)
• Mulch for moisture retention
• Well-draining soil

Planting Options

Step-by-Step Growing Guide

Step 1: Prepare the Soil

Onions need loose, well-draining soil rich in organic matter:

1. Work the soil 8-10 inches deep
2. Add 2-3 inches of compost
3. Test pH and adjust to 6.0-6.5
4. Rake smooth and remove debris

Step 2: Plant at the Right Time

Step 3: Proper Planting

For sets or transplants:

1. Space 4-6 inches apart in rows 12-18 inches apart
2. Plant sets 1 inch deep (tip just showing)
3. Plant transplants at the same depth they were growing
4. Water gently after planting

For seeds:

1. Sow 1/4 inch deep
2. Space 1 inch apart, thin to 4-6 inches
3. Keep soil consistently moist until germination (10-14 days)

Step 4: Ongoing Care

Watering:

• Provide 1 inch of water per week
• Keep soil evenly moist, not waterlogged
• Reduce watering when tops start to fall over

Fertilizing:

• Side-dress with nitrogen every 2-3 weeks
• Stop fertilizing when bulbs start to enlarge
• Avoid high-nitrogen fertilizers late in the season

Weeding:

• Keep beds weed-free (onions compete poorly)
• Hand-pull weeds to avoid disturbing shallow roots
• Mulch to suppress weeds and retain moisture

Step 5: Know When Bulbing Begins

Onions start forming bulbs when day length triggers the process:

• Tops stop producing new leaves
• Bases start to swell
• This is the critical growth phase

Common Problems and Solutions

Problem: Onions Not Bulbing

Cause: Wrong day-length variety for your region Solution: Plant appropriate varieties next season

Problem: Flower Stalks Forming (Bolting)

Cause: Temperature fluctuations or using large sets Solution: Use smaller sets (dime-sized), maintain consistent temperatures

Problem: Small Bulbs

Cause: Overcrowding or insufficient nutrients Solution: Thin properly, fertilize regularly

Problem: Soft or Rotting Bulbs

Cause: Overwatering or poor drainage Solution: Improve drainage, reduce watering

Harvesting Your Onions

Signs of Readiness

• Tops fall over and turn brown (60-80% of plants)
• Outer skin becomes papery
• Neck softens

Harvest Steps

1. Stop watering 1-2 weeks before harvest
2. Bend over any standing tops
3. Lift bulbs gently with a garden fork
4. Brush off soil (don't wash)
5. Leave tops attached for curing

Curing and Storage

Curing Process

1. Spread onions in a single layer
2. Place in warm (75-80°F), dry, well-ventilated area
3. Cure for 2-3 weeks until necks are completely dry
4. Tops should be papery and roots should be dry

Storage

• Trim tops to 1 inch and trim roots
• Store in mesh bags, braids, or single layers
• Keep in cool (35-45°F), dry location
• Check monthly and remove any spoiling bulbs

Quick Reference

Troubleshooting Guide

Next Steps

Once you've mastered basic onion growing, explore:

• Starting onions from seed for variety selection
• Growing perennial multiplier onions
• Trying specialty varieties like shallots and cipollini
• Season extension techniques for year-round harvests

Happy growing!