Growing onions successfully in North Florida depends on precise timing and selecting the correct variety. The mild winter climate and specific daylight requirements of the Allium cepa plant necessitate a different approach than in northern gardens. The foundation for a successful harvest is growing the plant through the cool season to maximize foliage development before the bulb forms. Planting at the wrong time or choosing an unsuited variety will result in small, underdeveloped bulbs.
Selecting Onion Varieties for North Florida
Onion bulbing is triggered by day length, a phenomenon known as photoperiodism. Onions are classified into three categories—short-day, intermediate-day, and long-day varieties—based on the sunlight hours required to initiate bulb formation. Given North Florida’s latitude, which has shorter daylight hours during the winter growing season, only short-day varieties are appropriate. These types require approximately 10 to 12 hours of daylight to transition from foliage growth to bulb production.
Planting a long-day variety will prevent the plant from forming a substantial bulb before the summer heat arrives. Gardeners must select varieties specifically labeled for southern regions due to this photoperiod sensitivity. Suitable short-day examples include:
- ‘Granex’ (the cultivar behind Vidalia onions)
- ‘Red Creole’
- ‘Texas Early White’
- ‘Texas Super Sweet’
Focusing on these varieties ensures the plant receives the correct environmental cue to develop a large, harvestable bulb.
Optimal Planting Schedule
The most effective planting window for onions in North Florida spans late fall and early winter, typically from late September through December. This timing allows the plants to establish a robust root system and significant leaf growth during the cooler months. The primary goal is to maximize the plant’s size before the increasing day length in late winter triggers the bulbing process.
The planting method determines the exact start date. If starting from seeds, sow them indoors as early as late August or September, six to eight weeks before the intended transplant date. Transplants, which are young seedlings sold in bunches, should be set out in the garden from late September to November. Transplants are often the preferred method as they offer a quicker path to harvest.
Planting too late leads to small bulbs because the plants lack time to grow large tops before spring bulbing begins. Planting too early, especially in September, risks exposing young plants to excessive heat, causing stress and poor development. Fall and early winter temperatures provide the consistent cool weather necessary for establishing foliage.
Planting Techniques and Soil Health
Successful onion cultivation requires preparing a loose, well-draining soil that permits the bulb to expand freely. North Florida’s often sandy soil can be improved by incorporating two to three inches of organic matter, such as compost or well-rotted manure, before planting. Onions prefer a slightly acidic to neutral soil pH, ideally between 6.0 and 6.8.
When planting transplants, they must be set shallowly. The roots and the base of the plant should be covered with no more than one inch of soil. Deep planting inhibits the natural swelling of the bulb above the soil line. Spacing the transplants about four to six inches apart allows each plant sufficient room for development.
Onions require consistent nourishment to produce large bulbs. Apply a complete balanced fertilizer at planting. After the plants are established, supplemental applications of nitrogen fertilizer every few weeks encourage robust leaf growth. Stop this frequent nitrogen feeding once the base of the plant begins to swell and the bulbing process is clearly underway.