Base all fertilizer and lime applications on a good soil test. Apply half the fertilizer at planting and the rest in two sidedress applications. A complete fertilizer program should include at least nitrogen, potassium, phosphorous, boron, magnesium and zinc. Make sidedress applications when the onions are three to four inches tall and again five to six weeks later. Most Vidalia types are transplanted, while scallions are usually direct-seeded.
Good transplants are about a quarter-inch thick.
Use only strong, disease-free transplants. Set them two inches deep into a moist seedbed. Seed green onions in the fall, late winter and early spring. Spring crops can be seeded from January to April, while fall crops can be seeded from August to early October. February and March are the safest times to seed in spring to avoid freeze damage.