In Florida, traditional bulbing onions should be planted between September and December. Look for short-day hybrids like the sweet-tasting Granex. This is the same type that's sold under the name Vidalia.
You can grow onions from seed, but it's quicker to plant sets. These small bulbs are ready to transplant and give you a head start for an earlier harvest.
Apply a complete balanced fertilizer when you plant. After that, apply a nitrogen fertilizer monthly and irrigate frequently to promote steady growth.
Your onions should be ready to harvest in four to five months, typically when one-quarter of the tops have fallen over.
- Florida Vegetable Gardening Guide
- Onions Are Nothing to Cry About (PDF)
- Sweet Onion and Strawberry Success in North Florida (PDF)