How to Grow Walla Walla Onion
Walla Walla Onion
Allium cepa var. walla walla
vegetableWalla Walla onions are a sweet, mild variety of bulbing onion known for their large size, golden-yellow skin, and exceptionally low sulfur content, which gives them a sweet flavor rather than the sharp bite typical of storage onions. These long-day onions require 14-16 hours of daylight to form bulbs and are best suited to northern regions. They are prized for fresh eating, grilling, and culinary applications where their sweetness can shine.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 3-7, particularly zones 4-6 where long daylight hours trigger bulbing
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Growth Stages
Seedling
2-3 weeksThin green shoots emerge from the soil; plants resemble small grass blades with minimal root development
Keep soil consistently moist but not waterlogged. Thin seedlings to proper spacing (4 inches). Provide ample light if growing indoors
Vegetative Growth
4-6 weeksFoliage develops rapidly with multiple green leaves and a thickening stem base. Small root system expands
Maintain even moisture and regular feeding with nitrogen-rich fertilizer every 2-3 weeks. Mulch to conserve moisture and suppress weeds
Bulb Formation
3-4 weeksAs daylength reaches 14-16 hours, the base of the plant begins to swell noticeably, forming a rounded bulb beneath the soil surface. Foliage remains green and vigorous
Continue consistent watering and balanced fertilization. This stage is crucial; inconsistent watering can cause misshapen bulbs. Remove flower scapes if they appear
Maturation & Curing
3-4 weeksFoliage yellows and begins to fall over naturally; bulb enlargement slows significantly. The papery outer skin develops its characteristic golden-yellow color
Reduce watering gradually as tops yellow. Allow 10-14 days of drying before harvest. Do not break down tops artificially; wait for natural senescence
Harvest & Storage
1 day (harvest), then 2-4 weeks curingTops are completely dried and brown; bulbs pull easily from the ground. Papery outer skin is fully formed and protective
Cure onions in a warm, dry, well-ventilated area for 2-4 weeks. Store in cool, dry conditions with good air circulation. Remove any soil before storage
Common Pests
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Use row covers over young plants; apply beneficial nematodes to soil; use sticky traps; remove infested plants immediately
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Spray with insecticidal soap or neem oil; encourage beneficial predators; avoid excessive nitrogen fertilization
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Row covers on transplants; remove infested plants; crop rotation; ensure soil is well-draining to reduce plant stress
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Improve air circulation; avoid overhead watering; remove infected leaves; fungicide application if severe
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Ensure excellent drainage; use disease-free sets; crop rotation (3-4 years); cull infected bulbs at harvest
Uses
Fresh eating and grilling
CulinaryWalla Walla onions are prized for raw consumption in salads, salsas, and chutneys due to their sweet, mild flavor. Their large size and tender texture make them ideal for grilling, caramelizing, and adding to sandwiches without the sharp bite of standard onions. [source]
Caramelizing and sauce base
CulinaryTheir natural sweetness intensifies when cooked slowly, making them exceptional for French onion soup, caramelized onion jams, and savory sauces. The low sulfur content prevents the harsh flavors typical of cooking storage onions. [source]
Quercetin and anti-inflammatory properties
MedicinalLike all onions, Walla Walla onions contain quercetin, a flavonoid with potential anti-inflammatory and antioxidant benefits. Regular consumption may support cardiovascular health and immune function. [source]
Natural pest deterrent
HouseholdThe strong sulfur compounds in raw onion juice can be used to create homemade pest repellents or companion planting strategies in the garden to deter certain insects and pests from vegetable beds. [source]
Pollinator attraction
WildlifeIf left to flower (allowing some bulbs to bolt), Walla Walla onions produce showy purple-pink flower heads that attract bees and other beneficial pollinators to the garden. [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 the majority of foliage has yellowed and fallen over, typically late July to August in northern regions. Gently pull bulbs from the soil; do not bruise them. Cure in a warm (70-85°F), dry, well-ventilated location for 2-4 weeks. Leave papery outer layers intact during curing. Once fully cured, store in a cool (32-40°F), dry area with 50-70% humidity. Properly cured Walla Walla onions can store 3-4 months, though they are best used fresh within the first 2 months due to their lower sulfur content and higher water content compared to storage onion varieties.
Fun Facts
- 🌱 Walla Walla onions are named after Walla Walla, Washington, where a French soldier named Peter Pieri brought seeds from Italy in the 1880s. The mild sweetness resulted from growing them in this specific region's climate.
- 🌱 Walla Walla onions are 'long-day' onions requiring 14-16 hours of daylight to form bulbs, making them unsuitable for southern gardens where daylength never reaches that threshold. Southern growers must use 'short-day' varieties instead.
- 🌱 These onions have a higher water and sugar content and lower sulfur levels than typical storage onions, which is why they are sweeter but do not store as long (3-4 months versus 6-8 months for storage varieties).
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