Growing Onions 101

Grow better onions with the right variety, better soil preparation, correct timing, and proper curing and storage.

Updated edition: 2026. Growing Onions 101 is a practical guide for home gardeners, allotment growers, homesteaders, small-space growers, and market gardeners who want to grow onions reliably from seed, sets, or transplants.

Onions look simple, but many disappointing harvests begin before planting: the wrong day-length variety, cold wet soil, poor pH, weak seedlings, oversized sets, too much nitrogen, too many weeds, pest pressure, disease, bad harvest timing, or poor curing before storage.

This guide explains how onions actually grow, why latitude and day length matter, and how to plan the season so your crop has the best chance of producing firm, useful bulbs that store well.

Inside, you’ll learn how to:

• Understand how onion bulbs form and why every healthy leaf helps build the final bulb
• Choose short-day, intermediate, or long-day varieties for your latitude and climate
• Compare storage onions, sweet onions, red onions, yellow onions, white onions, shallots, and spring onions
• Set a realistic sowing, transplanting, and harvest calendar for your region
• Use frost dates, soil temperature, elevation, and microclimate to avoid early-season mistakes
• Prepare soil with the right pH, drainage, organic matter, texture, and fertility
• Start onions from seed and understand when sets or transplants are the better choice
• Plant onions at the correct spacing, depth, and layout for beds, rows, raised beds, and containers
• Water onions correctly through establishment, active growth, bulbing, and the pre-harvest period
• Feed onions without creating soft, poorly storing bulbs
• Control weeds during the critical early growth window
• Identify common pests such as thrips, onion fly, allium leaf miner, and nematodes
• Recognize and reduce disease risks including downy mildew, white rot, neck rot, basal rot, and storage rots
• Harvest at the right time and avoid damaging bulbs before curing
• Cure onions properly for stronger skins, tighter necks, and longer storage life
• Store onions by variety type and understand why sweet onions cannot be turned into long keepers
• Grow shallots, spring onions, scallions, and onions in small plots, raised beds, and containers
• Plan a household onion supply or small market-garden crop with better records and fewer wasted bulbs
• Use, sell, dry, pickle, and preserve onions more confidently

The updated edition includes variety reference tables, planting and harvest calendar templates, soil preparation checklists, seasonal growing logs, pest and disease quick-reference charts, curing and storage references, troubleshooting guidance, a market-garden yield and cost estimator, glossary, and further reading.

This book does not assume you have a large plot or previous allium-growing experience. Whether you are growing thirty onions in a raised bed or planning a larger market-garden crop, the same principles matter: the right variety, the right timing, clean beds, steady growth, careful harvest, and proper storage.

If you want fewer small bulbs, fewer bolted plants, fewer storage losses, and a clearer plan from seed to store, Growing Onions 101 is your practical onion-growing guide.