Vegetable · Amaryllidaceae family
Welsh onion
Allium fistulosum
In short a 10-second read
Welsh onion (vegetable) grows to 0.3–0.9 m tall and 0.3–0.6 m wide when mature. It grows best in full sun to part shade, in average soil. Sow in March–August. Harvest in May–November. Hardy to −20 °C.
× spread 0.3–0.6 m
Where to plant
Sun, soil, frost.
It grows best in full sun to part shade, in average soil. Hardy to −20 °C.
Sun
Tolerates several positions — choose to suit the rest of the garden.
Soil and water
average · watering: moderate
Soil: loamy, humus-rich, sandy
Soil pH 6–7.5
Frost
It overwinters outdoors; in cold, windy spots winter protection is worth it.
How much space it takes
Mature size.
The mature plant next to a person (175 cm).
Next to a person
The final size depends on the cultivar and the spot — we give the range from smallest to largest.
Calendar
What to do and when.
Months for Central Europe. The line shows the current month.
The year at a glance
Sowing
direct sowing: March–August
Harvest
May–November
Winter protection
not needed
Overwintering
It copes with winter on its own.
It overwinters outdoors without protection, hardy to −20 °C.
- Needs no protection
- Hardy to −20 °C
- Dies back in winter and regrows in spring
Frequently asked
Quick answers.
When do I sow Welsh onion?
In March–August (direct sowing).
When is Welsh onion harvested?
In May–November.
Does Welsh onion tolerate shade?
It tolerates part shade (3–6 hours of sun), but not full shade.
How much space does Welsh onion need?
At maturity 0.3–0.6 m wide and 0.3–0.9 m tall; recommended spacing 20 cm.
Does Welsh onion survive winter outdoors?
Yes, without protection, hardy to −20 °C.
Where the data comes from
The data is indicative — we are still comparing it with further sources. Last checked 2 September 2026.
Show sources (4)
- Missouri Botanical Garden Plant Finder — Allium fistulosum
- Oregon State University Horticulture — Onions
- Wikidata (CC0) — Allium fistulosum
- Invasive plant lists — this species is not on them: EU
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