How to grow spring onion
Overview
Spring onion (Allium fistulosum) is a perennial onion grown for its tender leaves and small white bulbs. It is not a legume; this vegetable is prized for its mild flavour and easy, repeat harvests. Regular picking encourages more growth, making it a satisfying crop for home gardens.
Varieties
- White Lisbon — A popular, quick-maturing variety with crisp white stems and mild flavour; ideal for salads.
- Ishikura — Japanese bunching onion that forms no bulb; produces tall, slender white stems, very hardy.
- Evergreen Bunching — A perennial variety that regrows from division; good for continuous harvesting in all zones.
Soil Preparation
Prefers well-drained, loamy soil with pH 6.0–6.8. Enrich with aged compost or well-rotted manure before planting. Avoid heavy clay that retains water, as it can cause bulb rot.
Growing Guide
Sow seeds 5 mm deep, 2 cm apart in rows 15 cm apart. Thin seedlings to 5 cm spacing. Choose a full-sun position with well-drained, fertile soil. Keep soil consistently moist but not waterlogged. For continuous harvest, sow successive crops every 4-6 weeks. Established clumps can also be divided every 2-3 years to rejuvenate.
Sowing
Direct sow 5 mm deep, 2 cm apart in rows 15 cm apart. Germination takes 7–14 days at 15–20°C. Thin to 5 cm spacing once seedlings are 5 cm tall. Can also start in punnets and transplant, but direct sowing is simple.
Care
Apply a balanced liquid fertiliser every 3-4 weeks during active growth. Remove flower stalks promptly to keep plants producing leaves and bulbs. Divide clumps every 2-3 years to maintain vigour and prevent overcrowding.
Companion Planting
Spring onion grows well with carrots, lettuce, beetroot, and tomatoes. Avoid planting near beans and peas, as onions can inhibit their growth. The scent also helps deter some pests from neighbouring crops.
Common Pests & Risks
Thrips cause silver streaks on leaves; spray with insecticidal soap or neem oil. Rust appears as orange pustules; improve air circulation and remove affected leaves. Onion fly larvae tunnel into bulbs; use fine netting or exclude by rotating crops.
Harvesting
Harvest leaves when 15-20 cm tall by cutting 2-3 cm above the base; plants will regrow. Pull whole plants once bulbs reach 2-3 cm in diameter, typically 8-12 weeks after sowing. Regular trimming encourages fresh shoots.
In the Kitchen
Use fresh in salads, stir-fries, or as garnish. Store in the fridge for up to a week. Can regrow from root ends placed in water for a second harvest of greens.
Troubleshooting
Yellowing leaves: overwatering or nitrogen deficiency; adjust watering and apply liquid fertiliser. Bolting: caused by heat or stress; remove flower stalks and keep soil cool with mulch. Rust: orange pustules on leaves; space plants better and avoid overhead watering. Stunted growth: overcrowding; thin seedlings to 5 cm apart. Soft bulbs: soil too wet; improve drainage.