vegetableBiennialEdible

Onion

Allium cepa

Also known as: bulb onion, storage onion

Staple kitchen allium grown from seed, sets, or transplants. Choose long-day or short-day varieties based on latitude.

Growing Requirements

SunFull Sun

WaterMedium

Soil Type

Soil Drainage

Soil pH

Plant Spacing4–6″

Row Spacing12–18″

Planting Depth0.25–0.5″

Height12–18″

Spread4–6″

✓ Container Friendly✓ Raised Bed Friendly

Planting Schedule

Start Indoors

8–10 weeks before last frost

Direct Sow (Spring)

2–4 weeks before last frost

Transplant Outdoors

-4–9 weeks after last frost

Germination

7–14 days

Days to Harvest

90–120 days

Zone Suitability

USDA Hardiness Zones

Zones 3–9

Cannot overwinter outdoors

Long-day types for northern gardens, short-day for southern. Bulb size depends on day length.

Companion Plants

Good Companions (13)

Carrot

Daucus carota subsp. sativus

vegetable

Onion deters carrot fly; carrot deters onion fly

Confidence: High

Beet

Beta vulgaris

vegetable

Compatible root zones; onion deters pests from beets

Confidence: Medium

Lettuce

Lactuca sativa

vegetable

Onion scent deters aphids and slugs from lettuce

Confidence: Medium

Cabbage

Brassica oleracea var. capitata

vegetable

Onion scent deters cabbage worms and moths

Confidence: Medium

Broccoli

Brassica oleracea var. italica

vegetable

Allium scent deters cabbage moths from brassicas

Confidence: Medium

Strawberry

Fragaria × ananassa

fruit

Onion scent repels common strawberry pests

Confidence: Medium

Tomato

Solanum lycopersicum

vegetable

Onion deters aphids near tomato plants

Confidence: Medium

Spinach

Spinacia oleracea

vegetable

Onion deters pests; compatible cool-season companions

Confidence: Medium

Chamomile

Matricaria chamomilla

herb

Chamomile attracts beneficial insects and may improve onion vigor

Confidence: Low

Cauliflower

Brassica oleracea var. botrytis

vegetable

Onion scent deters cabbage pests from cauliflower

Confidence: Medium

Kale

Brassica oleracea var. sabellica

vegetable

Allium scent deters cabbage moths from kale

Confidence: Medium

Bell Pepper

Capsicum annuum

vegetable

Allium scent deters aphids from pepper plants

Confidence: Medium

Jalapeño Pepper

Capsicum annuum

vegetable

Allium scent deters pests from peppers

Confidence: Medium

Antagonists (3)

Green Bean

Phaseolus vulgaris

vegetable

Allium compounds inhibit the growth of beans

Confidence: High

Pole Bean

Phaseolus vulgaris

vegetable

Allium compounds inhibit the growth of beans

Confidence: High

Snap Pea

Pisum sativum var. macrocarpon

vegetable

Alliums inhibit nitrogen-fixing bacteria in legume roots

Confidence: Medium

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