Vegetable · Amaryllidaceae family
onion
Allium cepa
In short a 10-second read
Onion (vegetable) grows to 0.3–0.45 m tall and 0.15–0.3 m wide when mature. It grows best in full sun, in average soil. Plant out in March–April, October–November. Harvest in June–October.
× spread 0.15–0.3 m
Where to plant
Sun and soil.
It grows best in full sun, in average soil.
Sun
Elsewhere it will grow less well.
Soil and water
average · watering: moderate
Soil: humus-rich, loamy, sandy
Soil pH 6–8
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
Planting out
bulb: March–April, October–November
Harvest
June–October
Winter protection
does not overwinter
Frequently asked
Quick answers.
When is onion harvested?
In June–October.
Does onion tolerate shade?
No, it needs full sun.
How much space does onion need?
At maturity 0.15–0.3 m wide and 0.3–0.45 m tall; recommended spacing 10 cm.
Where the data comes from
We compared the data in 5 expert sources. Last checked 20 October 2026.
Show sources (5)
- NC State Extension Gardener Plant Toolbox
- RHS — How to grow onions
- Wikidata (CC0) — Allium cepa
- UMD Extension - Growing Onions
- Invasive plant lists — this species is not on them: EU
