How to Sow and Grow Spring Onions: A Complete Guide
Spring onions, also called scallions or bunching onions, are quick alliums harvested before a mature bulb forms. They need little space and fit between slower crops, along path edges and in containers. Succession sowing keeps stems tender and prevents gluts.
Choosing varieties
Some spring onions are immature bulb onions; true bunching onions divide into clumps and may be perennial. White, red and purple-stemmed cultivars are available. Choose winter-hardy varieties for autumn sowing and quick types for spring containers.
When to sow
Sow small batches every three to four weeks from early spring to late summer. In mild climates, sow hardy varieties in early autumn for overwintering. Under cover, late winter sowings provide an early crop.
How to sow
Sow 1 cm deep in drills 10–15 cm apart. Scatter seeds thinly or multi-sow 6–10 seeds per module and transplant the clump without separating it. Keep the surface moist until seedlings establish. Little thinning is needed for slim stems.
Soil and containers
Use sun or light shade and fertile, freely drained soil. Mature compost is generally sufficient. Containers only need to be 15–20 cm deep but must drain well. Sow across the pot, then repeat in another container several weeks later.
Watering and feeding
Water lightly but regularly so stems remain tender. Dry soil checks growth and strengthens flavour. Additional feed is rarely necessary in beds; container crops may need a dilute balanced organic feed after several weeks.
Keeping a steady supply
Protect early sowings with fleece and summer sowings with light shade during extreme heat. Pull whole clusters gradually, leaving smaller plants to grow. Resow as soon as a row begins to thin.
Common problems
Onion fly: cover with fine insect-proof mesh and rotate alliums
Allium leaf miner: use mesh during adult flight periods and remove infested plants
Rust: improve airflow and avoid excess nitrogen
Poor emergence: use fresh seed and keep shallow drills evenly moist
Bulbing too soon: choose bunching varieties and maintain steady growth
Harvesting and storing
Pull spring onions once stems are pencil thick or at the preferred size. Loosen dry soil first to avoid snapping them. Wash and use promptly; trimmed onions keep briefly refrigerated. Perennial bunching onions can be divided and replanted.
A reliable approach
Sow a short row or module clump every few weeks, keep shallow roots moist and harvest while stems are young. Their speed makes them ideal for filling temporary gaps.
