How to Grow Alliums (Onion, Garlic)

Alliums (Onion, Garlic)

Allium cepa (onion), Allium sativum (garlic)

vegetable

Alliums are pungent bulb vegetables belonging to the Amaryllidaceae family, prized for their culinary use and natural insecticidal properties. Both onions and garlic contain sulfur compounds that repel a wide range of garden pests, making them excellent companion plants. These cool-season crops are relatively easy to grow and store well after harvest.

Looking for a specific variety?

Yellow Sweet Spanish Walla Walla Red Burgundy Pearl Pickling German Extra Hardy Chesnok Red

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Example Alliums (Onion, Garlic) timeline · Pittsburgh, PA (Zone 6b)

Plant Alliums (Onion, Garlic)
Around Apr 17

Near Pittsburgh's average last spring frost.
Tend & protect
Late spring–summer

Watering, feeding, and pest-watch reminders.
Harvest Alliums (Onion, Garlic)
Around Jul 16

≈ 90 days after planting

Sample dates for Pittsburgh, PA. Sign up to get exact Alliums (Onion, Garlic) dates for your own zip code.

Growing Conditions

☀️

Sun: Full sun, 6-8 hours daily minimum

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Water: Moderate and consistent moisture; 1-1.5 inches per week. Reduce watering as bulbs mature to encourage proper sizing and storage quality. Avoid waterlogging.

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Spacing: 4-6 inches apart for onions; 6-8 inches for garlic inches

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Days to maturity: 90-150 days for onions from seed; 120-150 days for garlic from clove

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Planting depth: 0.5-1 inch for onion seeds; 1-2 inches for onion sets; 2 inches for garlic cloves

Soil

Type: Well-draining loamy soil rich in organic matter

pH: 6.0-7.0

Amendments:

Compost aged manure peat moss balanced fertilizer (10-10-10)

Growing Zones

Find your zone →

Zones 3-10; onions thrive in 5-8, garlic in 4-9

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

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Growth Stages

Sprouting & Root Development

2-4 weeks

Seeds or cloves germinate and develop root systems underground while green shoots emerge. Garlic typically takes 2-4 weeks to sprout; onion seeds 7-14 days.

Keep soil consistently moist but not waterlogged. Ensure good drainage to prevent rot. Maintain soil temperature 60-70°F for optimal germination.

Vegetative Growth

4-8 weeks

Foliage develops, with plants producing multiple leaves. Bulbs remain small and underground. This stage is critical for leaf and root development.

Water regularly, provide full sun. Fertilize every 3-4 weeks with nitrogen-rich fertilizer to support leaf growth. Remove any flower scapes from garlic. Mulch to retain moisture and suppress weeds.

Bulb Formation & Expansion

6-8 weeks

Underground bulb begins to enlarge as the plant channels energy downward. Foliage remains green and active. This stage typically begins 8-10 weeks after planting.

Transition to lower-nitrogen, higher-phosphorus fertilizer to support bulb development. Maintain consistent watering but begin reducing frequency slightly. Ensure adequate potassium for bulb quality.

Maturation & Dormancy

2-4 weeks

Foliage yellows and begins to die back as the plant matures. Bulb reaches full size and outer skin papery and dry. Roots naturally diminish.

Reduce watering significantly once foliage begins to yellow. Stop fertilizing. Do not disturb plants. Allow foliage to die back naturally—this seals the bulb and improves storage. Harvest when 50-75% of foliage has dried.

Harvest & Curing

1-4 weeks

Bulbs fully mature with dry, papery outer skin. Ready for harvesting and storage preparation.

Gently loosen soil and pull plants. Leave in field to dry for 1-2 weeks if weather permits, or cure indoors in a warm, airy space (70-80°F) for 2-4 weeks. Trim roots and dry foliage before storage.

Companion Planting

Plan your garden →

Plant with:

Brassicas (cabbage, broccoli) Carrots Lettuce Spinach Strawberries Tomatoes Peppers Chamomile Dill

Avoid planting near:

Beans Peas Asparagus Sage

Common Pests

Row covers on young plants, remove affected plants, crop rotation, ensure proper spacing for air circulation, sanitation of plant debris
Insecticidal soap, reflective mulches, neem oil, maintain humidity with consistent watering, remove infested foliage
Remove by hand, crop rotation (avoid planting after grass), trap crops (potato pieces), diatomaceous earth, maintain soil pH above 6.0
Collars around seedlings, shallow cultivation to disrupt soil, remove plant debris, beneficial nematodes, hand-picking
Adequate spacing for air circulation, spray with water, sulfur dusting, neem oil, increase humidity where possible
and
Hand-picking at dusk, copper tape barriers, slug traps, remove plant debris for shelter, encourage beneficial predators

Uses

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Staple Cooking Ingredient

Culinary

Onions and garlic are fundamental aromatics and flavor bases in cuisines worldwide, adding depth, pungency, and sweetness to soups, stews, stir-fries, and countless dishes. Fresh, caramelized, roasted, or raw, they are irreplaceable in the kitchen. [source]

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Immune System Support

Medicinal

Alliums contain allicin and sulfur compounds with antimicrobial, antiviral, and immune-boosting properties. Traditionally used in folk medicine to support respiratory health and reduce inflammation. [source]

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Natural Pest & Insect Repellent

Household

The sulfur compounds in alliums repel aphids, spider mites, Japanese beetles, mosquitoes, and many other garden pests and insects. Planting alliums near vegetables and ornamentals provides natural biological pest control without synthetic pesticides. [source]

🦋

Pollinator & Beneficial Insect Support

Wildlife

Garlic and onion flowers (if allowed to bolt) attract pollinators like bees and beneficial insects. These flowers are edible and ornamental, adding beauty while supporting garden ecology. [source]

🏠

Long-Term Storage & Preservation

Household

Properly cured alliums store for months in cool, dry conditions, providing year-round access to fresh garlic and onions. They can also be dried, pickled, or fermented for extended preservation. [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 when foliage yellows and falls over naturally (typically 4-5 months from seed). Gently loosen soil and pull when at least 50% of tops have dried. For garlic, wait until foliage is 50-75% brown and papery (typically June in northern zones). Cure onions and garlic in a warm, airy location (70-80°F) with good ventilation for 2-4 weeks before trimming roots and storing in cool, dry conditions (45-55°F, low humidity).

Fun Facts

🌱 Ancient Egyptians held garlic in such high regard that bulbs were placed in the tombs of pharaohs and used as currency to pay workers building the pyramids.
🌱 Garlic produces flower scapes—decorative, edible curled shoots—that should be removed from hardneck varieties to direct energy toward bulb development; the scapes themselves are prized in Asian cooking.
🌱 Alliums' pungent sulfur compounds (which make you cry when cutting onions) actually volatilize and dissipate over time, which is why cooked alliums taste sweeter and milder than raw ones.

Gardening Terms

New to gardening? Learn about terms used in this guide:

Full Sun Germination Mulch pH

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