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How to grow onions

Frost-hardy · Onion family

When to sow and plant

  • Start indoors 8–22 February
  • Plant out 22 March – 5 April

Based on: average for Germany, last frost 19 April, safe from 6 May

Planting calendar for your area
Where the dates come from

The weeks come from our sources; the dates use the average frost in Germany. Enter a German postcode to get dates for your area.

  • Start indoors: 8–10 weeks before the last frost (Cornell Home Gardening: Growing Guide Onions)
  • Plant out: 2–4 weeks before the last frost (Cornell Home Gardening: Growing Guide Onions)

Good and bad neighbours

Disputed · 2

  • CarrotDisputed· X

    Classic pairing against carrot and onion fly. Trials show slightly less carrot fly while onions are young; the Bavarian garden academy advises against it because nutrient and water needs differ.

    X: Sources disagree

    Carrot

  • White cabbage, Red cabbage, Savoy cabbage, Cauliflower, Broccoli, Brussels sprouts, Kale, Kohlrabi, Chinese cabbage, Pak choiDisputed· X

    Charts call onions a bad neighbour for cabbage. A field trial in India found fewer diamondback moth caterpillars next to onions.

    X: Sources disagree

    White cabbageRed cabbageSavoy cabbageCauliflowerBroccoliBrussels sproutsKaleKohlrabiChinese cabbagePak choi

Gardeners’ lore, not proven · 3

  • Zucchini (courgette)Lore: good· D

    Traditional advice, not tested.

    D: Tradition, named by at least two sources

    Zucchini (courgette)

  • CucumberLore: good· D

    Traditional advice, not tested.

    D: Tradition, named by at least two sources

    Cucumber

  • DillLore: good· D

    Traditional advice, not tested.

    D: Tradition, named by at least two sources

    Dill

Crop rotation

After the onion family, leave the bed free of it for at least 4 years.

  • The same species should go back to the same spot after a break of 3 years at the earliest.
  • Example: grown here in 2026, again from 2031.

At a glance

Family
Onion family (Amaryllidaceae)
Nutrient needs
Medium feeder
Frost
Hardy, tolerates frost
Spacing (row × plant)
25 × 5 cm (10 × 2 in)
Plants per m²
80
Per square foot (30 × 30 cm)
4 plants
Life cycle
Annual
Harvest
After 90–110 days from sowing

Spacing according to Bayerische Gartenakademie (LWG): Sä- und Pflanztermine auf einen Blick (2018). Other sources: 20–30 × 10–15 cm (8–12 × 4–6 in) (RHS Grow your own: Onions (Steckzwiebeln)); 30–46 × 8–10 cm (12–18 × 3–4 in) (UMN Extension: Growing onions (Saat)).

Questions and answers

When can I plant out onions?

Plant out, average for Germany: 22 March – 5 April. Enter a German postcode above for your area, or your own frost date in the planting calendar.

How far apart should I plant onions?

25 × 5 cm (10 × 2 in) (row × plant), according to Bayerische Gartenakademie (LWG): Sä- und Pflanztermine auf einen Blick (2018).

What grows well next to onions?

Carrot: Disputed (X), White cabbage, Red cabbage, Savoy cabbage, Cauliflower, Broccoli, Brussels sprouts, Kale, Kohlrabi, Chinese cabbage, Pak choi: Disputed (X), Zucchini (courgette): Gardeners’ lore, not proven (D), Cucumber: Gardeners’ lore, not proven (D) and Dill: Gardeners’ lore, not proven (D).

How long a break do onions need in the same bed?

After the onion family, leave the bed free of it for at least 4 years. The same species should go back to the same spot after a break of 3 years at the earliest.

More from the onion family

Sources

Show 17 sources
  1. Südtiroler Bauernbund: Merkblatt Fruchtfolgen im Gemüsebau (Oktober 2022)
  2. UMD Extension: Vegetables for Spring and Fall Planting
  3. Cornell Home Gardening: Growing Guide Onions
  4. Bayerische Gartenakademie (LWG): Sä- und Pflanztermine auf einen Blick (2018)
  5. RHS Grow your own: Onions (Steckzwiebeln)
  6. UMN Extension: Growing onions (Saat)
  7. NYC Parks GreenThumb: Square Foot Gardening (Growing Veggies in NYC Training)
  8. Landwirtschaftskammer Schleswig-Holstein: Fruchtfolge im Garten (Gartenmerkblatt, 2020)
  9. GBIF Backbone Taxonomy (über die GBIF-API, species/match)
  10. Bayerische Gartenakademie (LWG): Merkblatt 2104 Mischkulturen im Gemüsegarten (Mai 2020)
  11. BUND: Mischkultur – Gute und schlechte Nachbarn (August 2026)
  12. Gartenakademie Rheinland-Pfalz (DLR): Anbauplanung im Gemüsegarten (o. J.)
  13. RHS (Guy Barter): Three ways to use companion planting
  14. Uvah & Coaker 1984: Effect of mixed cropping on some insect pests of carrots and onions. Entomol. Exp. Appl. 36(2): 159–167 (Abstract via AGRIS)
  15. Gartenakademie Rheinland-Pfalz (DLR): Übersicht – Kultur verschiedener Gemüsearten im Hausgarten (o. J.)
  16. Sharma et al. 2022: Potentiality of intercropping in managing Diamondback moth (Plutella xylostella). Indian J. Agric. Sci. 92(8): 1010–1014
  17. Oregon State University Extension: Herbs and Flowers in the Vegetable Garden (o. J.)

Retrieved on 23 October 2026. Facts in our own words, one source per value.