Allium cepa
Onion
Common names: Bulb onion, Common onion
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.
Soil & site
Soil pH
Soil type
sandy, loamy, humus-rich, well-drained, nutrient-rich
Feeding
Light feeder
Companion planting
Good neighbors
carrot family (Apiaceae)
Umbellifers and alliums confuse each other's pests (carrot fly, onion fly).
For example celery rootParsleyCarrot fennelCorianderCelery (Stalk Celery)Caraway and 15 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 53 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 Red CloverRed CloverWhite CloverLupineWisteriaVelvet vetch and 18 more species in the catalogue
Source: basic crop‑rotation rule
nightshade family (Solanaceae)
Onions slow down the growth of nightshade family plants next to potatoes and tomatoes; the classic crop-rotation rule also applies in the bed side by side.
For example TomatoSweet pepperCocktail tomatoEggplantCape gooseberryChili and 8 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.
Diseases & pests
4 relevantFrom the knowledge base, automatically linked by affected species. How to spot and prevent them is covered in full in the lexicon.
Peronosporaceae
You will find that the False Mildew is not a true fungus, but an oomycete that comes from the underside of the leaf, unlike the True Mildew.
More on False MildewPuccinia allii
Leek rust is a fungal disease on leek, garlic, onion and chives. Bright orange yellow, elongated spore pustules form on the leaves and leaf sheaths, which burst open and dust off rust coloured powder.
More on Leek rustThysanoptera
Thrips are tiny, elongated insects that become particularly active on warm, muggy days, which is why they are also called thunderflies.
More on Thrips (thunderflies)Delia antiqua
The onion fly (Delia antiqua) lays its eggs on the leaf sheaths of young onion plants, and the larvae then tunnel into the bulb, the neck and the roots.
More on Onion flyVarieties
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
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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.