How to Grow Onion Ailsa Craig

Onion Ailsa Craig

Allium cepa 'Ailsa Craig'

vegetable

Ailsa Craig is a large, globe-shaped yellow onion variety prized for its mild flavor and exceptional size, often reaching 4-5 inches in diameter. Originally developed in Scotland, it's a long-day variety that produces uniform, golden-skinned bulbs with excellent storage capability. Known for being a premier exhibition onion, it's also excellent for cooking and fresh use.

Growing Conditions

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Sun: Full sun, 8+ hours daily (long-day variety benefits from extended daylight)

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Water: Consistent moisture during growing season, approximately 1-1.5 inches per week. Keep soil evenly moist but not waterlogged. Reduce watering as bulbs mature and tops begin to yellow.

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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: Plant sets 1-1.5 inches deep with tip just below soil surface; direct seed 0.5 inches deep

Soil

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

pH: 6.0-7.0

Amendments:

Compost or aged manure worked in before planting Balanced fertilizer (10-10-10 or similar) Sulfur if pH is above 7.0

Growing Zones

Find your zone →

Thrives in zones 3-8, prefers cooler growing seasons with longer day lengths

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

Growth Stages

Seedling/Set Stage

2-3 weeks

Small green shoots emerge from planted sets, developing first true leaves. Sets should be pea-sized to avoid bolting.

Keep soil consistently moist. Thin seedlings if direct seeding to proper spacing. Protect from birds if necessary.

Vegetative Growth

4-8 weeks

Vigorous green foliage develops with multiple leaves per plant. Bulbing has not yet begun; plants focus on leaf production.

Maintain steady moisture and regular fertilization (sidedress with balanced fertilizer every 3-4 weeks). Remove any flower shoots that form (bolting). Mulch lightly to retain moisture.

Bulb Initiation and Development

6-10 weeks

Base of plant begins to swell as day length increases and soil temperatures warm. Bulb enlargement becomes visible above soil surface.

Continue consistent watering and fertilization. Ensure good air circulation around plants. Hill soil slightly around developing bulbs if exposed. Monitor for pests.

Bulb Maturation

2-4 weeks

Bulbs reach full size with thick, papery golden-brown outer skin. Foliage begins to yellow and fall over as the plant reaches senescence.

Gradually reduce watering as tops yellow. Stop fertilizing. Do not break over foliage prematurely. Allow natural drying process.

Harvest and Curing

2-4 weeks curing

Tops are completely dry and fallen over. Bulbs are lifted and cured for storage. Papery skin is fully developed.

Cure onions in a warm (70-75°F), dry, well-ventilated location for 2-4 weeks before storing. Remove dried foliage once completely dry. Store in cool (50-55°F), dry conditions.

Companion Planting

Plan your garden →

Plant with:

Carrot Parsnip Beet Lettuce Spinach Chamomile Savory Dill Cabbage

Avoid planting near:

Asparagus Garlic Leek Other alliums Bean Pea

Common Pests

Spray with insecticidal soap or neem oil; encourage beneficial insects; remove debris; ensure adequate moisture to reduce stress
Use row covers during early growth; crop rotation; remove infested bulbs; apply beneficial nematodes to soil
and
Ensure well-draining soil; practice crop rotation (3-4 years); avoid overhead watering; remove infected plants immediately
Improve air circulation; avoid overhead irrigation; use fungicide if needed; plant resistant varieties in humid climates
Row covers; crop rotation; remove plant debris; fall cleanup to eliminate overwintering sites

Uses

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Mild Cooking Onion

Culinary

Ailsa Craig's mild, sweet flavor makes it ideal for caramelizing, roasting whole, or using fresh in salads and salsas. Its large size and dense flesh hold up well to cooking without becoming mushy. [source]

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Fresh Use and Slicing

Culinary

The crisp, juicy flesh and minimal tear-inducing compounds make this variety excellent for fresh eating and salads. Its size produces thick, uniform slices ideal for presentation. [source]

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Storage and Preservation

Household

Its exceptional keeping quality and sturdy papery skin make Ailsa Craig ideal for long-term storage without refrigeration. Properly cured bulbs can be stored through winter for gradual use. [source]

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Exhibition and Show Garden

Craft

Ailsa Craig is a premier exhibition onion, prized by gardeners and competitive growers for producing massive, perfectly uniform bulbs for county fairs and garden shows. [source]

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Nutritional and Health Benefits

Medicinal

Like all onions, Ailsa Craig contains quercetin and other antioxidants with potential anti-inflammatory and immune-supporting properties. Often used in traditional remedies for respiratory health. [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 foliage has completely yellowed and fallen over naturally, typically in late summer (August-September in Northern Hemisphere). Dig carefully to avoid bruising bulbs. Cure in a warm, dry, well-ventilated location for 2-4 weeks before storage. Store in mesh bags or braids in cool (50-55°F), dry conditions. Properly cured Ailsa Craig can store 4-6 months or longer.

Fun Facts

🌱 Ailsa Craig was developed in the mid-20th century on Ailsa Craig island (a volcanic rock formation in the Firth of Clyde, Scotland) and takes its name from this distinctive location.
🌱 This variety is a long-day onion that requires 14-16+ hours of daylight to trigger bulbing, making it particularly well-suited to northern regions with extended summer days but less ideal for southern zones.
🌱 Ailsa Craig holds numerous records in onion competitions and exhibitions, with specimens regularly exceeding 4 pounds and one authenticated record of over 7 pounds grown by a dedicated enthusiast.

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