How to Grow Ailsa Craig Onion

Ailsa Craig Onion

Allium cepa 'Ailsa Craig'

vegetable

Ailsa Craig is a large, golden-yellow globe onion variety prized for its mild, sweet flavor and excellent keeping quality. Originally developed in Scotland, it produces large bulbs weighing 1-2 pounds and is a popular exhibition and cooking variety. The plants are vigorous growers that perform well in most climates with proper care.

Growing Conditions

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Sun: Full sun, 8+ hours daily for optimal bulb development

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Water: Consistent moisture during growing season (1-1.5 inches weekly); reduce watering 2-3 weeks before harvest to encourage drying

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Spacing: 4-6 inches apart in rows 12-18 inches apart inches

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Days to maturity: 120-150 days from transplant

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Planting depth: Sets planted 1-1.5 inches deep; seeds 0.5 inches deep

Soil

Type: Well-draining, fertile loamy soil with high organic matter

pH: 6.0-7.5

Amendments:

Compost or aged manure Balanced fertilizer (10-10-10) Sulfur if pH is too high

Growing Zones

Find your zone →

Thrives in zones 3-9; best results in zones 5-8

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

Growth Stages

Seedling/Set Establishment

2-4 weeks

Small green shoots emerge from planted sets or seeds; root system developing underground

Keep soil consistently moist but not waterlogged; ensure adequate light if growing indoors; transplant seedlings at 2-3 true leaves

Vegetative Growth

6-8 weeks

Upright green foliage develops; plant builds leaf area; bulb begins to enlarge underground but remains small

Maintain consistent watering; apply balanced fertilizer monthly; keep bed weed-free; mulch to retain moisture and regulate temperature

Bulb Development

6-10 weeks

Visible swelling underground as bulb enlarges; foliage continues to grow; bulb skin begins to form

Reduce nitrogen fertilizer to avoid soft bulbs; maintain consistent moisture; ensure good drainage; continue weeding

Maturation

3-4 weeks

Bulb reaches full size (1-2 lbs); foliage yellows and begins to fall over; outer papery skin develops protective layers

Gradually reduce watering to help bulbs cure; do not fertilize; stop watering entirely when tops begin to collapse

Harvest & Cure

Harvest over 1-2 weeks; curing 2-3 weeks

Tops completely dry and fall over; bulbs ready for lifting and curing

Harvest when 60-70% of tops have collapsed; cure in warm, dry, well-ventilated location for 2-3 weeks before storage

Companion Planting

Plan your garden →

Plant with:

Beets Carrots Chamomile Lettuce Spinach Strawberries Tomatoes

Avoid planting near:

Beans Peas Sage

Common Pests

Use row covers during egg-laying periods; remove infested plants; apply neem oil; maintain good sanitation
Spray with insecticidal soap or neem oil; introduce beneficial insects; ensure adequate moisture
Cover with row fabric early season; remove affected bulbs; solarize soil before planting
Use disease-free sets; practice crop rotation; ensure good drainage; avoid overhead watering
Improve air circulation; avoid overhead watering; apply sulfur or copper fungicides if needed

Uses

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Sweet eating and cooking

Culinary

Ailsa Craig onions are mild and sweet with low pungency, making them ideal for fresh eating, salads, sandwiches, and caramelizing. Their large size and tender texture make them perfect for grilling, roasting, and French onion soup. [source]

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Exhibition variety

Culinary

These large, uniform bulbs with attractive golden skin are prized for agricultural shows and competitions. Growers often thin to single bulbs per plant to maximize size. [source]

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Long-term storage

Household

With excellent keeping quality and thick, protective papery skin when properly cured, Ailsa Craig onions store exceptionally well for 4-6 months, providing reliable onions throughout fall and winter. [source]

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Nutritional and health benefits

Medicinal

Like all onions, Ailsa Craig contains quercetin and other antioxidants with potential anti-inflammatory properties, plus vitamin C and fiber. Regular consumption may support heart health and immune function. [source]

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Pollinator garden benefit

Wildlife

Allowing some onions to bolt and flower produces attractive umbel blooms that attract bees and other pollinators while providing seeds for next season. [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 when 60-70% of tops have fallen over and dried, typically in late July-August depending on region. Gently lift bulbs with a garden fork, disturbing soil as little as possible. Cure bulbs in a warm (80-85°F), dry, well-ventilated location for 2-3 weeks until necks are completely dry and papery. Store in cool (32-40°F), dry conditions with good air circulation; properly cured Ailsa Craig keeps 4-6 months.

Fun Facts

🌱 Ailsa Craig was developed in the 1880s on the island of Ailsa Craig off the Scottish coast and quickly became one of the most popular onion varieties worldwide for both exhibition and kitchen gardens.
🌱 The variety produces exceptionally large bulbs under good conditions—some prize-winning specimens exceed 2 pounds—and was specifically bred for size and keeping quality.
🌱 Unlike many large onions, Ailsa Craig retains a mild, sweet flavor even at large sizes, making it one of the few exhibition varieties that tastes as good as it looks.

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