Growing Onion in a pot

Onions have a low water requirement once established, but consistent moisture is important during bulb formation in late spring and early summer. Water during dry spells, aiming for about 2–3 cm per week, but reduce watering as the foliage begins to yellow in July or August—wet conditions at this stage can encourage rot and reduce storage life. Avoid overhead watering if possible, as wet foliage increases the risk of downy mildew. Feed once in April with a balanced general-purpose fertiliser or a light dressing of blood, fish, and bone. Onions don't need heavy feeding—too much nitrogen produces soft, leafy growth and poor bulbs. If your soil is reasonably fertile, feeding may not be necessary at all. Weeding is the most important maintenance task. Onions have shallow roots and struggle to compete, so hand-weed carefully and regularly, especially in the first two months. Mulching lightly between rows helps, but keep mulch away from the bulb necks. Onion white rot is the most serious disease: it causes yellowing foliage and a white fungal growth on the bulb base. There is no cure, and the spores persist in soil for many years, so crop rotation is essential. Onion fly larvae tunnel into young bulbs, causing collapse; covering rows with insect mesh after planting offers good protection. Downy mildew appears as greyish fuzz on leaves in damp seasons—improve air circulation and avoid overhead watering. Onions are fully hardy and need no winter protection. Harvest in July, August, or September when the tops collapse, then cure and store in a cool, dry, frost-free place.