Planting and care
How to grow onions
When to grow
Cool/Warm season · Annual
How to start
Seed, sets, transplants or cloves
Mature size
Upright foliage 8–24 in
Time to harvest
About 90–120 days from sets or transplants; seed-grown bulbs often take 120–150 days or more.
Feeding needs
Moderate feeder
Growth habit
Allium
How to prune
Do not bend or cut healthy tops to force maturity; leaves feed the bulb. Remove flower stalks early and use bolted onions first because they store poorly.
How to harvest
Lift when bulbs are full size and most tops naturally fall over. Dry in a shaded, airy place until necks and skins dry; stop routine watering as mature tops fall.
Harvest and kitchen use
Cooking, seasoning, fresh garnish and storage depending type
Nutrition and garden value
Vitamin C and sulfur-containing compounds
Narrow upright growth makes good use of bed edges and gaps
Common challenges and troubleshooting
Thrips, bulb rot and poor drainage