Allium cepa
Onion
Common names: Bulb onion, Common onion
At a glance
- Light
- Full sun
- Spacing
- 10 cm, rows 25 cm
- Lifespan
- Biennial
- Planting
- Mar–Apr
- Harvest
- Jul–Aug
- Hardiness
- Cold damage below −10 °C
- Water need
- Medium
Photo: Mehdi · CC BY-SA 3.0 · Source
Description
The onion belongs in every kitchen and is child's play to grow from sets. In mixed culture with carrots it is a proven duo, as the two drive each other's pests away.
Care instructions
Push the sets into the soil from March so the tip just shows, in a sunny, rather dry spot. Keep the bed free of weeds and stop watering as soon as the foliage yellows; then the onion ripens into a storable harvest.
The care notes were machine-translated from German.
Garden year
PlantingMar–Apr
HarvestJul–Aug
Soil & site
Soil pH
Soil type
sandy, loamy, humus-rich, well-drained, nutrient-rich
Onions need a loose, well-drained soil without waterlogging; a sandy-loamy, humus-rich site is ideal. Loosen heavy soils beforehand with mature compost and a little sand, and improve very sandy ones with compost; avoid fresh farmyard manure, because it encourages rot.
Alliums (onion, garlic, leek) are moderate feeders. A 4-year break prevents onion rot and leek moth. They make good neighbours for carrots.
Feeding
Light feeder
Months
Mar–May
Prepare the bed in spring with a little mature compost; as a light feeder, the onion needs no more. Largely skip additional nitrogen, and from the end of May do not feed at all, so that the onion ripens instead of just producing foliage.
Overwintering
In normal summer cultivation, the onion is a storage crop: as soon as about two thirds of the foliage has wilted and flopped over in summer, pull the onions from the soil and let them dry off in an airy, shady spot until the skin is paper-dry. Then store them cool, dark and dry in open nets or ventilated wooden crates (no plastic, otherwise moisture builds up). Do not leave ordinary summer onions in the bed; they rot in wet and frost. Only specially bred winter sets overwinter in the soil, if they have formed pencil-thick shoots before the frost.
Propagation
Methods
- From seed
- Offsets
You propagate the onion in two proven ways: by sowing (seed onion method) or by sets (small daughter bulbs raised in advance).
Sowing: Start onions from mid-February to early March indoors or in a greenhouse: about 2 cm deep, a few seeds per pot, at around 15 to 20 °C (germination in 2 to 4 weeks). Once the young plants are strong enough and night frost is no longer a threat (mid to late April), plant them outdoors: 5 to 10 cm apart in the row, 20 to 25 cm between rows, in full sun. Direct sowing outdoors is possible from March/April, as soon as the soil is frost-free; seed drill about 2 cm deep.
Sets: Sets are small daughter bulbs about the size of a hazelnut, grown from a dense sowing the previous year, the simpler and faster method because they are more certain to reach harvest. Plant them from the end of March to April so that only the tip just shows, 5 to 10 cm apart in the row and about 20 to 25 cm between rows. Choose a sunny, warm spot. Harvest once the foliage has turned yellow, flopped over and largely dried; with spring planting typically from July to September. After harvest, let them dry off well before you store the onions.
Companion planting
Good neighbors
carrot family (Apiaceae)
Umbellifers and alliums confuse each other's pests (carrot fly, onion fly).
For example CeleriacParsleyFlorence fennelCorianderCelery (Stalk Celery)Caraway and 17 more species in the catalogue
Source: classic companion planting (DACH-Gartenpraxis)
rose family (Rosaceae)
You can plant garlic and chives under strawberries and roses; their scent repels aphids and other pests.
For example StrawberryAppleRaspberryClimbing rosePearAronia and 59 more species in the catalogue
Source: Bio-Gärtnerei Mixed Culture Practice
Rather not
legume family (Fabaceae)
particularly well establishedAllium species inhibit the nitrogen‑fixing rhizobia of legumes through their root exudates, which slows their growth.
For example Crimson cloverRed CloverWhite CloverLupineWisteriaHairy vetch and 23 more species in the catalogue
Source: basic crop‑rotation rule
Companion planting is partly traditional gardening lore. Where the reason is known, it is given.
Some of these explanations were machine-translated.
For signed-in gardeners
Sign in to see symptoms, severity, season and prevention for every one of your plants.
Free account, set up in 30 seconds.
For your garden
Grow Onion yourself
Gartenkern tells you when frost is coming, when to sow and when to harvest, for your location.
Free, no time limit
Varieties
6 varieties‘Ailsa Craig’
An old Scottish variety known for its exceptionally large, straw‑yellow onions, the bulbs become quite substantial with good care.
‘Hyred F1’
A modern red hybrid onion, valued for its strong dark red skin and its good tolerance of downy mildew, a real advantage especially in wet summers.
‘Red Baron’
Probably the most popular red onion for the home garden, with a deep red skin and flesh coloured intensely red right through, which lifts any salad visually.
‘Rote Laaer’
An old Austrian landrace from the Weinviertel with flat round, red brown bulbs and a strongly spicy aroma.
‘Sturon’
One of the most reliable onion sets of all, with round, evenly sized bulbs, firm golden brown skins and very good keeping quality well into winter.
‘Stuttgarter Riesen’
The proven classic for sets and seed, with flat, round, golden brown bulbs and a robust, spicy flavour that stores well through the winter.
Notes from real gardens
What other gardeners have written down about this variety, anonymous and voluntary.
No notes shared yet. Will you be the first to write one down?
From the magazine
Planting or sowing onions: three routes to your own harvest
Three routes lead to your own onion: the fast set, the cheap seed onion and the early overwintering onion. Here they stand side by side, plus the trick against bolting and the classic bed duo with the carrot.
Companion planting the old way: what holds up about the classic bed partnerships
Carrot and onion, tomato and basil, the Three Sisters: what generations observed in the bed, how much of it is actually documented, and which neighbours you really do need to keep apart.
Planting and earthing up leeks: how the long white shaft grows
The long white shaft makes a good leek. How to plant leeks deep, earth them up right, and protect them from leek moth and onion fly with a net.
August in full swing: harvest, preserve and sow again
August is the month of full baskets: tomatoes, beans and onions come in by the crateful. Now you preserve what you can't eat straight away and sow the greens that will see you through winter. That's how you stay well fed through the cold months.