How to Grow Ailsa Craig Red Onion
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Ailsa Craig Red Onion
Allium cepa 'Ailsa Craig'
vegetableAilsa Craig Red is a large, globe-shaped onion variety prized for its mild flavor and sweet taste. Originally developed in Scotland, it produces copper-red bulbs that can reach 4-5 inches in diameter and weigh up to a pound or more. This heirloom variety is excellent for fresh eating, storage, and exhibition purposes.
When should you plant Ailsa Craig Red Onion in your zone?
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Example Ailsa Craig Red Onion timeline · Pittsburgh, PA (Zone 6b)
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Plant Ailsa Craig Red Onion
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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Harvest Ailsa Craig Red Onion
Around Aug 15≈ 120 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Ailsa Craig Red Onion dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 3-9; prefers cooler to moderate climates
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Get my Ailsa Craig Red Onion timeline →Growth Stages
Seedling
2-3 weeks from seed, immediate if planting setsThin, grass-like green shoots emerge from seed; small white root system developing below soil. Sets appear as small bulblets if using sets for propagation.
Keep soil consistently moist but not waterlogged. Thin seedlings to proper spacing once 2-3 inches tall. Maintain steady moisture to prevent stunting.
Early Growth
4-6 weeksGreen foliage grows 8-12 inches tall, developing multiple leaves. Underground, bulb swelling begins as root system strengthens and lateral roots spread.
Maintain consistent watering and apply balanced fertilizer every 3-4 weeks. Keep area weed-free to reduce competition. Mulch lightly to retain moisture.
Bulb Development
6-8 weeksFoliage reaches 12-18 inches; visible bulging occurs below soil surface as days lengthen in spring and early summer. Bulbs swell rapidly during this phase.
Water deeply and consistently (1-1.5 inches weekly). Side-dress with nitrogen-rich fertilizer mid-season to support continued growth. Hill soil slightly around developing bulbs if needed. Continue weeding and mulching.
Maturation
3-4 weeksBulbs reach full size (4-5+ inches diameter) with papery outer skin developing. Foliage begins to yellow and topple over as plants signal readiness for harvest.
Reduce watering as tops brown; stop watering once 75% of foliage has collapsed. Do not fertilize. Allow bulbs to cure in ground for 1-2 weeks if weather permits and ground is dry.
Harvest & Curing
2-4 weeks curingBulbs pulled when tops are completely brown and dry. Outer papery skin is firm and copper-colored. Roots have dried completely.
Cure bulbs in warm, dry, well-ventilated location (70-75°F) for 2-4 weeks before storage. Brush off soil gently; trim tops to 1 inch once fully dried. Store in cool, dry place (32-40°F, low humidity).
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Use row covers over young plants; practice crop rotation; apply beneficial nematodes; avoid fresh manure in planting area
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Spray with insecticidal soap or neem oil; increase humidity; remove infested leaves; encourage beneficial insects
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Ensure good air circulation; avoid overhead watering; apply sulfur or copper fungicide; remove affected foliage; plant resistant varieties nearby
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Use row covers early in season; remove and destroy affected plants; practice sanitation; rotate crops
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Practice strict crop rotation (7-10 years); destroy affected plants; disinfect tools; avoid wet conditions; use fungicide if available
Uses
Fresh eating and mild dishes
CulinaryAilsa Craig Red's sweet, mild flavor makes it ideal for eating fresh in salads, slicing for sandwiches, and using in dishes where a gentle onion presence is desired. The thin skin and tender flesh are particularly appealing when served raw. [source]
Caramelization and cooking
CulinaryThe high sugar content in Ailsa Craig Red makes it excellent for caramelizing, roasting, and grilling, developing deep sweetness and rich flavor when cooked slowly. [source]
Storage and preservation
HouseholdWhen properly cured, Ailsa Craig Red bulbs store exceptionally well for 3-6 months, making them valuable for year-round home use and preserving the harvest through winter months. [source]
Exhibition and showing
CraftAilsa Craig Red is a classic exhibition onion variety, prized by gardeners who compete at fairs and shows for its large size, uniform globe shape, and attractive copper-red appearance. [source]
Quercetin and antioxidants
MedicinalLike all onions, Ailsa Craig Red contains quercetin and other antioxidants associated with anti-inflammatory properties, supporting general health and wellness when consumed regularly. [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 browned and dried (typically mid-to-late summer). Gently loosen soil and pull bulbs by hand or dig carefully to avoid bruising. Allow bulbs to cure in a warm, dry, well-ventilated area for 2-4 weeks before storage. For storage, keep bulbs in a cool (32-40°F), dry location with low humidity; they can store 3-6 months when properly cured. For eating fresh, harvest anytime after bulbs reach desired size.
Fun Facts
- 🌱 Ailsa Craig Red originated on the small Scottish island of Ailsa Craig in the Firth of Clyde, where it was developed in the 19th century and became renowned worldwide as a classic heirloom variety.
- 🌱 This variety can produce bulbs weighing over one pound and reaching 5+ inches in diameter under ideal growing conditions, making it a favorite among gardeners seeking record-breaking specimens.
- 🌱 Ailsa Craig Red onions are famous among exhibition gardeners and can be dried and stored for 6+ months when properly cured, making them both a culinary choice and a winter storage staple.
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