You don't have to buy onions in the store when you can grow your own green onions or dry onion bulbs in your Floridian backyard. The state's warm climate lets you start planting onions earlier than cooler states: mid-September in northern Florida, and October in central or southern Florida, according to the University of Florida. Onion varieties that thrive in Florida include the Granex, Savannah Sweet and White Portugal.
Use a spade to break up the soil to a depth of 6 to 8 inches. Remove any rocks or similar debris and ensure the dirt has no large clumps. Such debris or clumps will impede bulb development.
Amend the soil by stirring in 2 to 3 inches of aged compost, which keeps the soil loose, adds nutrients and helps the dirt retain moisture. Follow with an application of standard 10-10-10 all-purpose garden fertilizer. Spread at the rate listed on the bag as potency varies by product.
Plant the onion sets 1 inch deep. If you are growing green onions, space bulbs so they almost touch one other. If you are growing dry onions, space the bulbs 4 inches apart. If you are growing more than one row of onions, space each row by 14 to 18 inches, according to the University of Florida.
Water the planted sets to moisten soil to a depth of 6 inches. Repeat once a day in the early morning so excess moisture can burn off in the afternoon, thereby reducing the risk of mold and fungus on the bulb.