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HarvestBench

Roots & alliums · Overview

How to Grow Onions

Onions care about day length as much as soil. Long-day types belong in the North; short-day types in the South. Raised beds drain well, which onions like, as long as you do not let them dry to dust.

Key growing facts for Onions
Spacing4–6 in for bulbs; closer for bunching onions
SoilLoose, fertile, well-drained
Sunlight8+ hours
Planting depthSets: tip showing; plants: about as deep as they grew
WaterEven while bulbing; ease off as tops fall
Days to harvestOften 90–120 days from plants or sets

Soil requirements

  • They are moderate feeders. Compost plus a light nitrogen feed if plants are pale — label rates only.
  • Weeds compete badly. A clean, mulched bed matters.

Watering

  • Keep moisture even until tops start to yellow and fall. Then cut back so bulbs cure.

Sunlight

Full sun. Shade from tomato cages makes skinny bulbs.

Planting

  • Sets are easy; plants (transplants) often make better storage bulbs.
  • Match variety to your latitude. This is not optional trivia.

Spacing

  • 4–6 inches for bulb onions. Square-foot: 9 per square is a common pattern.

Common problems

  • Bolting

    Big sets, or a cold snap after growth starts. Use smaller sets.

  • Rot

    Poor drainage or watering after tops have fallen.

Helpful tools

  • The plant spacing calculator
  • A dry rack for curing

Product links will be added when independently researched. See the garden tools hub for buying criteria.

Frequently asked questions

Why are my onions all neck and no bulb?

Wrong day-length type for your region, too much shade, or crowding. Check the variety group before you buy sets next year.