How to Grow Spring Onions

Overview

Spring onions are quick-growing, mild-flavoured alliums that are perfect for salads, stir-fries, and garnishes. They take up very little space and can be grown in borders, containers, or between rows of slower crops. With successional sowing, you can enjoy fresh spring onions from late spring through to autumn.

Health Benefits

Vitamins K and C: Spring onions are a good source of Vitamin K for bone health and blood clotting, along with Vitamin C for immune support.

Folate and antioxidants: They provide folate for healthy cell division and contain flavonoid antioxidants that may help protect against oxidative stress.

Freshest when homegrown: Low in calories and packed with micronutrients, spring onions are at their nutritional peak when picked just minutes before eating, making them one of the best arguments for growing your own.

Soil Preparation

Spring onions grow in most well-drained, fertile soils. They are not demanding but appreciate a position in full sun with soil that has been improved with compost. The ideal pH is 6.0 to 7.0. They grow excellently in containers and window boxes, making them ideal for small gardens or balconies.

Sowing & Planting

Sow seeds directly outdoors from March to August in drills 1cm deep, spacing rows 10-15cm apart. Sow thickly as spring onions are harvested whole and do not need thinning. For earlier crops, sow hardy varieties in September for overwintering and spring harvest. Make successional sowings every 3-4 weeks for a continuous supply.

Care & Maintenance

Water regularly to keep the soil moist and promote fast, tender growth. Weed carefully as spring onions are poor competitors. They need no feeding if the soil is reasonably fertile. Cover overwintering crops with cloches or fleece for protection in colder areas.

Harvesting

Pull spring onions when the stems are pencil-thick, typically 8-12 weeks after sowing. They can be harvested younger as baby onions for extra-mild flavour. Pull as needed and use immediately for the best taste. Do not leave them too long or the bulbs will begin to swell and the flavour becomes stronger.

Common Problems

Onion fly can attack spring onions, causing yellowing and wilting. Cover with fine mesh and practise crop rotation.

Downy mildew may appear in wet conditions. Ensure good air circulation and avoid overhead watering.

Bolting can occur with overwintered crops in spring. Harvest promptly once they resume growth.

Companion Planting

Spring onions grow well alongside carrots and lettuce, with the allium scent helping to deter carrot fly. Avoid planting near beans and peas, as alliums can hinder their development.