When to Plant and Harvest Onion
Essential culinary allium with pungent bulbs for cooking and fresh use
Soil pH: Target soil pH 6.5. Lime if a soil test reads below 6.0. Keep it within 6.0 to 7.0. Soil Test Desk
Curing and storage: Store at 32 to 40F and 65 to 70% humidity. Keeps 1 to 8 months, pungent types longest. Cure: 2 to 3 weeks warm, dry, and airy, until the necks are dry. Do not store onions in plastic bags. Use mesh bags or slatted crates. Harvest Storage Desk
How many to grow for what you cook: Fresh salsa (pico de gallo), Canned tomato salsa, Weeknight marinara, Greek salad. Plate to Plot planner
Pets: Toxic to dogs and cats (ASPCA). ASPCA says cats are more susceptible to onion family plants, but dogs are also at risk depending on the amount eaten. Fence or raise the bed. ASPCA entry. Pet-Safe Garden Finder
Best Time and Place to Plant Onion
In USDA zone 7, the typical spring window is March 1 to May 1. Cooler zones usually plant later; warmer zones plant earlier.
Plant Onion in a spot with 6+ hours of direct sun, soil warmed to 50F to 80F, and enough room for 4 inches between plants and 12 inches between rows.
Related Planting Guides
Planting Windows by Zone
| Zone | Spring | Fall |
|---|---|---|
| Zone 1 | May 1 to June 15 | August 1 to August 30 |
| Zone 2 | April 20 to June 10 | August 10 to September 15 |
| Zone 3 | April 10 to May 30 | August 15 to September 30 |
| Zone 4 | April 1 to May 20 | August 20 to October 1 |
| Zone 5 | March 20 to May 15 | August 25 to October 10 |
| Zone 6 | March 10 to May 10 | September 1 to October 20 |
| Zone 7 | March 1 to May 1 | September 10 to November 1 |
| Zone 8 | February 15 to April 20 | September 20 to November 15 |
| Zone 9 | February 1 to April 10 | October 1 to December 1 |
| Zone 10 | January 15 to March 30 | October 15 to December 15 |
| Zone 11 | Year-round | Year-round |
| Zone 12 | Year-round | Year-round |
| Zone 13 | Year-round | Year-round |
Spacing and Care
- Planting depth: 0.5 inches deep
- Spacing: 4 inches apart, 12 inches between rows
- Soil temperature: 50F to 80F
- Sunlight: 6+ hours
- Watering: 1 inch per week; reduce when tops begin to fall over
- Days to harvest: 100
Fertilization
- High-nitrogen 21-0-0 synthetic: Side-dress every 3-4 weeks until bulbing
- Blood Meal organic: 1.5 lbs per 100 sq ft before planting
- Compost organic: 2 inches worked in before planting
Companion Plants
- Carrots
- Lettuce
- Beets
- Tomatoes
- Chamomile
Avoid Planting Near
- Beans
- Peas
- Asparagus
Check any pair, and see which pairings have research behind them, on the Companion Planting Desk.
Harvest Signs
- Tops have fallen over and dried (80% lodging)
- Neck is soft when squeezed
- Papery outer skin has formed
- Cure in warm, dry location 2-4 weeks before storage
Track picks and rate the season on the Harvest Log.
FAQs
When should I plant Onion?
Onion planting depends on your USDA hardiness zone. In USDA zone 7, the typical spring window is March 1 to May 1. Cooler zones usually plant later; warmer zones plant earlier.
What is the best time of year to plant Onion?
The best time of year to plant Onion is when your zone planting window is open and soil temperatures are around 50F to 80F. In USDA zone 7, the typical spring window is March 1 to May 1. Cooler zones usually plant later; warmer zones plant earlier.
Where is the best place to plant Onion?
Plant Onion in a spot with 6+ hours of direct sun, soil warmed to 50F to 80F, and enough room for 4 inches between plants and 12 inches between rows.
How far apart should I plant Onion?
Plant Onion about 4 inches apart, with rows around 12 inches apart.
What grows well with Onion?
Onion is commonly paired with Carrots, Lettuce, Beets, Tomatoes, Chamomile.
How long does Onion take to grow?
Onion is typically ready to harvest in about 100 days under good conditions. Use the harvest signs below rather than the calendar alone.
How do I know when to harvest Onion?
Harvest Onion when tops have fallen over and dried (80% lodging). Neck is soft when squeezed Papery outer skin has formed