Onion (sets)
Vegetable · cool season
When to plant
- Sow seeds outdoors about 5 weeks before your average last spring frost.
- Ready to harvest about 100 days after planting.
Harvest when tops fall over; cure 2 weeks.
Frost dates depend on where you live. Enter your ZIP code to get exact dates.
Dates by zone: 3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a 9b 10a 10b
Growing basics
Harmful to pets. Every part is toxic to cats and dogs, raw or cooked. It damages their red blood cells.
- Sun
- Full sun (6+ hours)
- Spacing
- 4 in
- Soil temperature
- At least 45°F
- Time to harvest
- About 100 days
- Containers
- At least 2 gallons
- Plant family
- Onion family (alliums)
- Harvest per plant
- About 0.4 lb
- Seeds keep
- About 1 year
Companions
Good neighbors: Carrot, Beet, Lettuce, Tomato, Cabbage
Keep apart: the bean and pea family (legumes). Onions and garlic can stunt beans and peas.
Keep apart: Asparagus. Onions and garlic can stunt asparagus.
Keep apart: Horseradish. Horseradish spreads aggressively. Give it its own spot.
Keep apart: Mint. Mint spreads aggressively into neighbors. Keep it in a pot.
Keep apart: Fennel (bulb). Fennel slows the growth of most garden plants. Grow it on its own.
Keep apart: Sunchoke (Jerusalem artichoke). Sunchokes spread aggressively and shade neighbors.
Varieties to try
- Texas Grano 1015Y 100 days: short-day sweet onion (south of about 35°N)
- Candy 100 days: intermediate-day sweet onion (about 35–42°N)
- Walla Walla 110 days: long-day sweet onion (north of about 37°N)
- Yellow Sweet Spanish 110 days: long-day, large bulbs
Pests and problems
Grow it well
Tips
- Dry onions and garlic before storing them. Pull onions once most of their tops have flopped over, and garlic once the lower third of its leaves turn brown. Spread them somewhere airy and out of the sun for 2 to 3 weeks, until the necks are dry and papery.
- Try winter sowing in milk jugs. Cut a milk jug almost in half, poke drainage holes in the bottom, and fill it with moist potting mix. Sow cold-hardy seeds like kale, onions, or native flowers, tape the jug shut with the cap off, and set it outside in late winter. The seeds sprout when the weather is right, already used to the cold.
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