🧅 Onion
Allium cepa
vegetables
bulb vegetable (allium)
☀️ Sun
Full sun (6, 8+ hours); day length triggers bulbing , choose correct variety for your latitude (short-day for south, long-day for north)
💧 Water
Medium; 1 inch per week; consistent moisture during bulbing; reduce/stop watering when tops begin to fall over to promote curing
🗺️ Zones
3, 4, 5, 6, 7, 8, 9, 10
🧪 Soil pH
6.0, 7.0 (slightly acidic to neutral)
🪴 Soil Type
Well-drained, fertile loam with moderate organic matter; lighter soils produce better bulbs; heavy clay can cause thick necks and poor storage
🚿 Drainage
Good drainage critical; onions rot in waterlogged soil; raised beds recommended in clay soils
📏 Spacing
Sets/plants 4, 6 inches apart in rows 12, 18 inches apart; close spacing produces smaller bulbs; wider spacing for large slicing onions
⏱️ Maturity
90-150 days (from transplant/sets); 100-175 days from seed depending on day-length type
🍴 Edible Parts
🍽️ Bulb
🍽️ Green tops (scallions/green onions)
🍽️ Flower stalks (scapes , milder than bulb)
Key:🤝 Grows well together❌ Keep apart☀️ Sun needs💧 Water🗺️ Hardiness zone
🤝 Companions (10)
Onions repel many beet pests; beets grow at different root depth; complementary growth habits
Onions repel cabbage moths and aphids; both are cool-season crops that grow well together.
Onions repel carrot rust fly; carrots deter onion fly , classic and highly effective mutual pest-repelling partnership; probably the most proven companion planting combination
Improves onion flavor and growth; antifungal properties may reduce onion diseases; attracts beneficial insects
Onions deter aphids and cabbage worms from kale with their sulfur compounds.
Lettuce grows quickly in the space between onions; onions repel lettuce pests like aphids and slugs
Onions repel slugs and many strawberry pests; strawberries act as living mulch
Improves onion growth and flavor
Onions repel spider mites and aphids from tomatoes; though alliums are less effective near solanaceous crops than near carrots
⚠️ Keep Apart (3)
⚠️ Bean (all types)
Alliums inhibit Rhizobium bacteria , beans will be stunted if planted near onions; one of the strongest documented antagonisms
Same reason as beans , alliums inhibit nitrogen-fixing bacteria crucial for legumes
May stunt onion growth; aromatic incompatibility (some sources report mutual antagonism)
💊 Medicinal Uses
Medicinal Properties
- Contains allicin and quercetin , antimicrobial, anti-inflammatory, and antioxidant compounds
- Traditionally used for colds, flu, and respiratory infections; may reduce blood pressure and cholesterol
- Contains prebiotic fibers (inulin) supporting gut microbiome
- Topical: onion juice used traditionally for wound healing, ear infections, and insect stings
📝 Growing Notes
Day length determines bulbing: short-day onions (10-12 hrs daylight) for zones 7+, long-day (14-16 hrs) for zones 6 and colder. Onions can be grown from seeds, sets (small bulbs), or transplants. Cure after harvest: dry in warm, ventilated area for 2-3 weeks until necks are tight and dry. Store in cool, dark, dry place (not refrigerator). Never plant onions where any Allium has grown in 3+ years.
🛒 Buy Seeds & Plants
Baker Creek Heirloom Seeds
Johnny's Selected Seeds
Botanical Interests
True Leaf Market
Burpee
Territorial Seed Company
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