How to Grow Allium (Onion/Garlic)

Allium (Onion/Garlic)

Allium cepa (onion), Allium sativum (garlic), Allium fistulosum (bunching onion)

vegetable

Alliums are cool-season bulbing or non-bulbing vegetables in the amaryllis family, characterized by pungent sulfur compounds that give them their distinctive flavor and aroma. They range from large storage onions to delicate spring onions and hardneck garlic, offering diverse culinary applications. Most species are biennial, forming bulbs in their first year and flowering in the second.

Looking for a specific variety?

Yellow Sweet Spanish Ailsa Craig Walla Walla Red Burgundy Spanish Roja Candy Egyptian Walking Onion Scallion German Extra Hardy Music German Extra Hardy Chesnok Red French Pinkroot

Growing Conditions

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Sun: Full sun, 8+ hours daily (minimum 6 hours for bunching onions)

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Water: Consistent moisture, 1-1.5 inches weekly; reduce watering as bulbs mature and approach harvest. Avoid waterlogging. Drier conditions in final 3-4 weeks improve storage quality.

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Spacing: 4-6 inches between plants for bulbing onions; 2-3 inches for bunching onions and garlic cloves; 12 inches between garlic rows inches

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Days to maturity: Onions: 100-150 days from seed/transplant; Garlic: 210-240 days (planted fall, harvested summer); Bunching onions: 60-120 days

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Planting depth: Seeds: 0.25-0.5 inch; Sets (small bulbs): 1-2 inches, pointed end up; Garlic cloves: 2 inches, pointed end up, 2 inches between cloves

Soil

Type: Well-draining, fertile loamy soil rich in organic matter

pH: 6.0-7.0

Amendments:

Compost or aged manure (2-3 inches worked in) Balanced fertilizer (10-10-10) Bone meal for phosphorus Avoid fresh manure which encourages disease

Growing Zones

Find your zone →

Zones 3-9 for most Alliums; garlic prefers 3-8 with cold dormancy; onions adaptable across all zones with variety selection

2a 2b 3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a 9b

Growth Stages

Germination/Emergence

7-14 days for germination; 2-3 weeks to visible growth

Thin, grass-like shoots emerge from soil; seedlings appear thread-like for 1-2 weeks before developing visible leaf structure

Keep soil consistently moist but not waterlogged. Thin seedlings to proper spacing early to avoid root competition. Provide full sun.

Leaf Development (Vegetative)

6-10 weeks from emergence

Multiple linear leaves develop, plant builds foliage mass; photosynthesis fuels bulb enlargement. Garlic develops 6-8 leaves before bulbing.

Water consistently 1-1.5 inches weekly. Apply balanced nitrogen fertilizer monthly. Mulch to retain moisture and regulate soil temperature. Remove flower scapes on garlic to redirect energy to bulbs.

Bulking/Bulb Formation

4-8 weeks

Base of plant swells as carbohydrates concentrate in bulb; outer leaves begin to yellow and dry. Cloves in garlic become distinct and separate within bulb.

Reduce nitrogen, apply phosphorus-potassium fertilizer if needed. Decrease watering frequency—soil should be moist but not wet. Avoid disturbing bulbs. Hill soil around developing bulbs for blanching in some varieties.

Maturation/Harvest Readiness

2-4 weeks

Tops collapse and dry down; bulb scales firm and papery; outer skins develop characteristic color. Plant enters dormancy. Garlic scapes flower and begin to brown.

Stop watering 2-3 weeks before harvest to cure bulbs in ground. Do not fertilize. Monitor for bolting in onions (remove flower buds if plant flowers prematurely). Leave garlic in ground for 1-2 weeks after tops dry.

Curing (Post-Harvest)

2-4 weeks curing; then long-term storage (6+ months possible)

Harvested bulbs dry with necks sealed and outer scales hardened; color deepens. Garlic develops papery wrapper and sweet, mellow flavor.

Cure in warm (70-75°F), dry, well-ventilated area for 2-4 weeks. Do not wash until after curing. Store in cool (32-40°F), dry location with 50-60% humidity. Braid garlic or store in mesh bags for airflow.

Companion Planting

Plan your garden →

Plant with:

Brassicas (cabbage, broccoli, kale) Carrots Beets Lettuce Spinach Strawberries Tomatoes (some gardeners report benefit) Chamomile Dill Marigolds

Avoid planting near:

Beans (inhibits nitrogen fixation) Peas (same nitrogen competition) Asparagus Sage Parsley (some competition) Other Alliums too close (disease spread, cross-pollination)

Common Pests

Row covers over seedlings; crop rotation; remove damaged bulbs; apply beneficial nematodes; diatomaceous earth around base
Strong water spray to dislodge; reflective mulch; neem oil spray; insecticidal soap; encourage predatory insects
Handpick if numbers low; Bacillus thuringiensis (Bt); spinosad; row covers; eliminate weeds as alternative hosts
Use resistant varieties; avoid overwatering; remove infected bulbs; practice 3-4 year crop rotation; improve drainage
Improve air circulation and spacing; avoid overhead watering; copper fungicide; resistant varieties; remove infected leaves
Crop rotation (7+ years); remove and destroy infected plants; solarization; avoid contaminated soil; no known cure, prevention essential
Proper curing and low-humidity storage; avoid mechanical damage at harvest; ensure adequate spacing for air circulation
and (Ditylenchus spp.)
Hot water seed treatment (118°F for 30 minutes); resistant varieties; crop rotation; solarization

Uses

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Fundamental cooking ingredient

Culinary

Onions and garlic are essential aromatic base vegetables in cuisines worldwide, used raw, caramelized, roasted, or in stocks. They add depth, sweetness (when cooked), and pungency (when raw) to savory dishes. [source]

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Immune support and cardiovascular health

Medicinal

Garlic and onions contain allicin and other sulfur compounds with antibiotic, antifungal, and anti-inflammatory properties. Traditional use and modern studies support consumption for immune function, blood pressure regulation, and cholesterol management. [source]

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Fermented and preserved preparations

Culinary

Onions and garlic are pickled, fermented, or made into vinegars, sauces (like romesco), and condiments. Garlic confit (slow-cooked in oil) is a versatile preparation for long-term storage. [source]

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Natural pest deterrent

Household

Crushed garlic or onion spray functions as a mild insecticide and fungicide in the garden, deterring soft-bodied insects and some fungal pathogens. Often used in organic integrated pest management. [source]

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Bunching onions and scallions

Culinary

Tender green onion tops and white stalks are eaten raw in salads, as garnish, or lightly cooked. Garlic scapes offer a mild garlic flavor and are excellent in stir-fries or pesto. [source]

This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.

Harvest Tips

Harvest onions and garlic when 50-75% of tops have yellowed and fallen over. Gently loosen soil with a fork and pull bulbs, leaving roots and 1 inch of stem attached. Do not wash before curing. For bunching onions, harvest outer leaves when 6-8 inches tall and plant continues producing; or pull entire plant when mature. Garlic scapes (flowering stems) are edible and should be harvested when they curl, about 30 days before bulb harvest, to maximize bulb size.

Fun Facts

🌱 Garlic was historically believed to provide strength and endurance to workers and soldiers; Roman soldiers were issued garlic rations, and it remains a symbol of vitality across many cultures.
🌱 The sharp bite of raw onions and garlic comes from thiosulfate compounds that break down into volatile sulfurous gases when cells are damaged—cooking inactivates these enzymes, making alliums sweet and mild.
🌱 Garlic is actually a bulb made of 8-20 smaller bulblets called cloves, each capable of growing into a full bulb; a single clove planted in fall can produce a bulb containing 8-20 new cloves by summer.

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