Onion in March: monthly care

Onions thrive in full sun and need well-drained soil to prevent bulb rot. Sandy soil and loam are ideal; heavy clay should be improved with grit and organic matter several weeks before planting. Choose an open site that hasn't grown onions, garlic, or leeks for at least three years to reduce the risk of disease. You can grow onions from sets (small immature bulbs) or from seed, though sets are far more reliable for most gardeners. Plant sets in March or April, once the soil has warmed slightly and is workable. Push each set gently into the soil so that the tip just shows above the surface, spacing them 10 cm apart in rows 25–30 cm apart. If birds pull them up in the first few days, replant immediately and consider covering the row with fleece or netting until the roots take hold. If sowing from seed, start indoors in modules in late winter or sow directly outdoors in March or April. Sow thinly, about 1 cm deep, and thin seedlings to 10 cm apart once they're large enough to handle. Transplant module-grown seedlings at the same spacing when they reach pencil thickness. After planting, water gently to settle the soil around the roots, but avoid waterlogging. Onions dislike competition, so keep the area weed-free from the start—their shallow roots make hoeing risky later on. A light mulch of well-rotted compost between rows helps suppress weeds, but keep it clear of the necks of the bulbs to prevent rot. Avoid planting in freshly manured ground, as this encourages lush foliage at the expense of bulb development.