[header] How to grow sweet onions [title] Aim to plant in early to mid spring. [step] Your onions will have the best chance if they're grown in loose, fertile, and well-draining soil with a ph between 6.0 and 6.8. Use a tiller to break up the soil in the garden bed. 
Spread 2 inches (5 cm) of mature compost or aged manure over the garden bed and work it into the soil with the tiller. [substeps] You can test the ph of the soil with a home soil test kit or with a ph meter.