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Growing onions in home gardens

A quick guide to onions

  • You can grow onions from seed, transplants or small bulbs called “sets.”
  • Plant onions early in spring.
  • Soil for onions should be well-drained and high in organic matter.
  • Onions are shallow-rooted and require constant moisture for proper growth.
  • Harvest onions when about half the tops are falling over and dry.
  • Curing is essential if you want to store onions. You must dry them in a warm, dry, well-ventilated area.
Person holding freshly harvested onion.

Long-day and short-day onions 

Onions (Allium cepa) have relatives that include garlic, chives, leeks and shallots.

Storage onions grown in Minnesota generally are “long-day” types that require 14 or more hours of daylight to form bulbs. All onions require full sun for best growth. Overcast skies and cool temperatures during the growing season will delay bulb formation.

Sweet or mild onions are "short-day" onions. Although you can grow them in Minnesota, they will generally develop small bulbs. Bunching onions, including scallions and Egyptian walking onions, have green stalks.

Planting

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How to keep your onion plants healthy and productive

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Managing pests and diseases

Many things can affect onion bulbs and leaves. Changes in physical appearance and plant health can be caused by the environment, plant diseases, insects and wildlife. In order to address what you’re seeing, it is important to make a correct diagnosis. 

You can find additional help identifying common pest problems by using the online diagnostic tools What insect is this? and What's wrong with my plant? or by sending a sample to the UMN Plant Disease Diagnostic Clinic. You can use Ask a Master Gardener to share pictures and get input.

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Authors: Marissa Schuh,  Extension educator and Cindy Tong, Extension  horticulturist

Reviewed in 2022

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