Growing Guide
How to Grow Onions
A complete, definitive, simple, and free guide to growing big onions in your own yard.
Selecting the Type of Onion to Grow
Onions come in three types, short-day, intermediate-day, and long-day onions.
Short Day: Grown in Southern US regions where daylight doesn’t vary much throughout the year and winters are mild.
Intermediate Day: Typically grown in the middle of the US, but can be grown in both the South and the North.
Long Day: Typically grown in northern states where daylight is much longer in the summer than in the winter.
Onions Growing Profile
Sunlight
The amount of sunlight an onion needs to form a full-size bulb depends on the type of onion.
Short-Day Onions: 10-12 Hours Direct Sun
Intermediate Onions: 12-14 Hours Direct Sun
Long-Day Onions: 14-16 Hours Direct Sun
Soil
Well-draining, sandy loam is best.
Will grow in clay if amended with 50/50 compost.
Grow best with pH between 6.2 and 6.8.
Soil should be rich in nitrogen.
Water
Seedlings: Keep top 2” consistently moist.
Early Growth: About 1” of water every 4 days
Bulb Formation: Increase water to 2” every 4 days
Late Growth: Decrease water to 1.5” every 4 days
Stop watering 1-2 weeks before harvest when leaves fall over.
Soil Temperature
For Vegetative Growth: 55°F to 75°F
For Bulb Development: 60°F to 77°F
Cold Tolerance: 35°F
Heat Tolerance: 85°F
Extreme temperatures or frequent fluctuations can cause onions to bolt prematurely.
