To plant onion sets successfully, follow these steps:
- Soil preparation: Choose well-draining, loose soil with a pH between 6.0 and 6.8. Raised beds or loose garden soil enriched with compost or well-rotted organic matter work best. Avoid heavy clay soils and acidic conditions (below pH 6.5)
- Planting depth and spacing: Plant onion sets about 2 cm (¾ inch) deep or just deep enough so the pointed tip or sprouted green end is barely showing above the soil surface. Space sets 5–10 cm (2–4 inches) apart in rows 25–30 cm (10–12 inches) apart. Some sources recommend 3–4 inches apart and rows 12–16 inches apart, which also works well
- Orientation: Plant sets with the pointed or sprouted end facing upward and the root end down. For unsprouted sets, the top usually ends in a point, and the bottom is blunter with root remnants
- Planting method: You can plant sets in shallow drills or gently push them into loose soil. Firm the soil around them and water well after planting. Cover with fleece if birds are a problem until the sets root in
- Timing: Plant onion sets in early spring once the soil is workable and has warmed to about 45°F (7°C), typically around the last frost date. In some regions, autumn planting is possible with cold-tolerant varieties
- Container growing: If growing in containers, use a pot at least 45 cm (18 inches) wide and deep with peat-free compost. Position in a warm, sunny spot and water regularly
This approach ensures good root establishment and encourages healthy bulb development for a successful onion crop.
