How to Grow Alliums (Garlic, Onions)

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Alliums (Garlic, Onions)

Allium sativum (garlic), Allium cepa (onion)

vegetable

Alliums are pungent bulb-forming plants in the Amaryllidaceae family, prized for both culinary use and natural pest deterrent properties. Garlic and onions contain sulfur compounds that repel or kill many common garden pests. These cool-season crops are relatively easy to grow and provide dual benefits as food and garden protectors.

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When should you plant Alliums (Garlic, Onions) in your zone?

Get a personalized planting timeline — when to start seeds, transplant, and harvest — based on your USDA zone and local frost dates. Free to start.

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

Plant Alliums (Garlic, Onions)
Around Apr 17

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

Watering, feeding, and pest-watch reminders.
Harvest Alliums (Garlic, Onions)
Around Nov 8

≈ 210 days after planting

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

Growing Conditions

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Sun: Full sun, 6-8 hours daily minimum

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Water: Moderate and consistent; 1-1.5 inches per week. Keep soil evenly moist but not waterlogged. Reduce watering as bulbs mature.

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Spacing: 4-6 inches apart for individual cloves/sets; rows 12-18 inches apart inches

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Days to maturity: Garlic 210-240 days (fall-planted); Onions 90-120 days depending on variety and day-length sensitivity

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Planting depth: 2-3 inches for garlic cloves (pointed end up); 1-2 inches for onion sets or seeds

Soil

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

pH: 6.0-7.0

Amendments:

Compost aged manure bone meal fish emulsion

Growing Zones

Find your zone →

Thrive in zones 3-9; garlic prefers cooler zones (3-7), onions more versatile (3-9)

1a 1b 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

Green shoots emerge from soil; roots establish from clove/bulb base. Cool temperatures promote root growth.

Ensure consistent soil moisture but avoid waterlogging. Mulch lightly to retain moisture and regulate soil temperature. Plant in fall (garlic) or early spring (onions).

Leaf Growth (Vegetative)

4-8 weeks

Multiple green leaves develop; plant builds leaf area and establishes strong foliage. Visible above-ground growth accelerates.

Maintain consistent moisture and provide nitrogen-rich fertilizer (compost tea or balanced fertilizer). Weed regularly. Monitor for pests but seldom needed at this stage due to allium's natural defenses.

Bulbing (Transition)

4-6 weeks

Plants sense day-length changes; bulb formation initiates at soil base. Above-ground growth slows, energy shifts to bulb development.

Reduce watering slightly. Stop nitrogen fertilization to avoid excessive foliage at expense of bulbs. Ensure plants have adequate phosphorus and potassium.

Bulb Maturation & Dormancy

2-4 weeks

Bulbs swell underground; foliage yellows and begins to fall over. Papery skin forms, protecting bulb.

Reduce watering significantly. Allow foliage to naturally decline. Stop all fertilization. Ensure good air circulation to prevent rot.

Harvest & Curing

Harvest over 1-2 weeks; curing 2-4 weeks

Foliage fully yellow or brown; tops fall over completely. Bulbs ready for harvest.

Harvest when foliage is 50-80% brown. Cure in warm, dry, well-ventilated location for 2-4 weeks. Store in cool, dry conditions.

Companion Planting

Plan your garden →

Plant with:

Tomatoes peppers lettuce brassicas (cabbage, kale, broccoli) roses fruit trees carrots strawberries spinach

Avoid planting near:

Beans peas asparagus sage (garlic only)

Common Pests

Use row covers at planting; remove affected plants; encourage beneficial predators; maintain crop rotation; practice good sanitation
Spray with neem oil or insecticidal soap; encourage beneficial insects; ensure adequate water to reduce stress; remove heavily infested leaves
Row covers during egg-laying period; handpick larvae; bacillus thuringiensis (Bt) spray; encourage parasitic wasps
Increase humidity and watering frequency; spray with water jet to dislodge; neem oil; predatory mites
Crop rotation (3-4 years); resistant varieties; solarization; avoid contaminated equipment; remove infested plants
Ensure excellent drainage; avoid overhead watering; cure bulbs properly before storage; select disease-resistant varieties; practice crop rotation

Uses

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Flavor enhancement & cooking staple

Culinary

Garlic and onions are fundamental aromatic vegetables in virtually all cuisines worldwide. They add depth, sweetness, and complexity to soups, stews, stir-fries, roasted vegetables, and countless other dishes. Garlic becomes sweet and mellow when roasted; onions caramelize to rich, savory depth. [source]

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Natural pest deterrent & botanical insecticide

Pest management

Allium sulfur compounds (allicin, diallyl disulfide) repel aphids, spider mites, Japanese beetles, carrot flies, and cabbage moths while serving as companion plants. Garlic or onion spray (homemade from crushed cloves infused in water) acts as both repellent and contact insecticide when applied to affected plants. [source]

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Immune support & cardiovascular health

Medicinal

Garlic contains bioactive compounds believed to support immune function, reduce inflammation, and promote cardiovascular health. Raw or lightly cooked garlic retains more of its beneficial sulfur compounds; traditionally used in herbal medicine for respiratory and circulatory support. [source]

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Natural cleaning & antimicrobial agent

Household

Garlic's antimicrobial and antifungal properties make it useful for household cleaning solutions. Garlic-infused water or oil can be used to clean surfaces and inhibit mold growth; traditionally used to treat fungal issues in stored produce. [source]

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Pollinator support & biodiversity

Wildlife

Allium flowers (edible and ornamental) provide pollen and nectar to bees, butterflies, and beneficial insects mid to late season when other food sources may be scarce. Allowing some plants to flower supports beneficial insect populations that prey on garden pests. [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 garlic when 50% of foliage has yellowed (typically June-July in Northern Hemisphere). Harvest onions when tops fall over and outer skin papery (July-August). Dig carefully with fork to avoid bruising. Cure in warm, dry, well-ventilated area for 2-4 weeks. For green onions, harvest at any size by pulling or cutting 1 inch above soil. Store cured bulbs in cool (32-50°F), dry, low-humidity conditions.

Fun Facts

🌱 A single garlic bulb can produce 4-20 cloves depending on variety, allowing gardeners to multiply their crop year after year by replanting cloves.
🌱 Garlic and onions have been cultivated for over 5,000 years and appear in ancient Egyptian tombs, suggesting their valued role in both cuisine and spiritual practice.
🌱 The 'garlicky' odor on your hands comes from sulfur compounds that can be partially removed by rubbing hands on stainless steel under running water—the reaction breaks down the volatile compounds.

Gardening Terms

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

Compost Full Sun Mulch pH

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