How to grow Onion Sets (Radar, Autumn)

Allium cepa

🥕 Vegetable 🌱 Grown each year

A very hardy overwintering onion: plant sets in autumn and lift golden bulbs in early summer, weeks before spring-planted onions.

At a glance: Sow early September to early October, harvest from early May.

When to sow, plant and harvest

JanFebMarAprMayJunJulAugSepOctNovDec

Sow outdoors

Harvest

Timed for a typical UK garden (last frost mid-April). The app uses your own town's frost dates.

Early September – early October · 6 weeks before the first autumn frost
Plant Sets
Plant sets 10 cm, rows 30 cm apart apart in rows.
21–45 days after “Plant Sets” · Late September – mid October
Look for Shoots
Green shoots should be showing. Keep weeds down — these crops hate competition.
120–150 days after “Look for Shoots” · Late January – late February
Spring Feed
Give a general feed as growth restarts in spring.
21–35 days after “Spring Feed” · Mid February – late February
Weed and Water
Hoe off weeds between rows and water in dry spells — even moisture gives better crops.
240–280 days after “Plant Sets” · Early May – mid June
Harvest
Lift in June or July once the leaves topple over.
7–21 days after “Harvest” · Early May – late May
Dry and Store
Dry well; overwintered onions keep until about Christmas.