How to Grow Walla Walla Onion

Walla Walla Onion

Allium cepa 'Walla Walla'

vegetable

Walla Walla onions are a sweet, mild variety of bulbing onion known for their large size, golden-yellow skin, and low sulfur content that creates their characteristically sweet flavor. Originally developed in the Walla Walla Valley of Washington state, these onions are perfect for fresh eating, grilling, and caramelizing. They are a long-day variety, thriving in northern climates and producing impressive yields when grown in optimal conditions.

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 per week. Reduce watering 2-3 weeks before harvest to promote curing and storage quality.

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

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Days to maturity: 100-120 days from transplant; 180-210 days from seed

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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

pH: 6.0-7.0

Amendments:

Compost or aged manure Balanced fertilizer (5-10-10) Sulfur to lower pH if needed

Growing Zones

Find your zone →

Ideal in zones 4-8; performs best in northern regions with long summer daylight

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

Growth Stages

Seedling/Set Establishment

2-3 weeks from planting

Green shoots emerge from onion sets or seeds; small roots develop. Plants are delicate and tender.

Keep soil consistently moist but not waterlogged. Thin seedlings to proper spacing. Protect from harsh winds.

Vegetative Growth

4-6 weeks

Rapid leaf development with 4-6 green leaves per plant. Root system expands significantly. No bulbing occurs yet.

Apply balanced fertilizer every 2-3 weeks. Maintain consistent watering. Remove weeds regularly to reduce competition. Mulch to retain moisture.

Bulbing Initiation

4-6 weeks

Leaf growth slows; base of plant begins to swell as daylight hours increase. Bulb formation begins underground.

Continue watering consistently. Monitor for pests and diseases. Reduce nitrogen fertilizer to encourage bulbing rather than leaf growth.

Bulb Maturation

3-4 weeks

Significant bulb enlargement; outer layers dry and papery. Leaves begin to yellow and fall over as plant maturity nears.

Reduce watering frequency to stress plants slightly and concentrate sugars. Do not fertilize. Watch for lodging (fallen tops).

Harvest and Cure

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

Tops completely brown and dry; bulbs fully mature with papery outer skin. Ready for pulling and curing.

Pull when 75-80% of tops are down. Cure in warm, dry, airy location for 2-3 weeks. Store in cool, dry place with good air circulation.

Companion Planting

Plan your garden →

Plant with:

Carrots Lettuce Beets Chamomile Dill Strawberries Basil

Avoid planting near:

Beans Peas Asparagus Sage Parsley

Common Pests

Use row covers early in season; remove infested plants; apply spinosad-based insecticides; rotate crops yearly
Spray with neem oil or insecticidal soap; maintain consistent moisture to reduce stress; remove heavily infested leaves
Improve air circulation; avoid overhead watering; apply copper fungicide preventatively; remove affected leaves
Use disease-free sets; practice crop rotation; maintain proper drainage; discard infected bulbs immediately
Use cutworm collars around young plants; hand-pick at night; apply diatomaceous earth around base

Uses

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Fresh Eating and Slicing

Culinary

Walla Walla onions are renowned for their exceptional sweetness and mild flavor, making them ideal for eating raw in salads, sandwiches, and salsas. Their low sulfur content produces a crisp, non-pungent taste. [source]

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Grilling and Caramelizing

Culinary

The high sugar content in Walla Walla onions makes them exceptional for grilling, roasting, and caramelizing. They develop rich, sweet, complex flavors when cooked slowly at low temperatures. [source]

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Onion Rings and Frying

Culinary

Their large size and natural sweetness make Walla Walla onions ideal for battered onion rings, tempura, and deep frying applications. [source]

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Natural Dye

Household

Onion skins can be used to create natural yellow and orange dyes for fabric, fiber arts, and craft projects through boiling and fermentation. [source]

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Culinary Medicine and Wellness

Medicinal

Onions contain quercetin and other flavonoids with anti-inflammatory and antioxidant properties, supporting immune function and cardiovascular health 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 75-80% of tops have dried and fallen over, typically mid-July to mid-August in northern regions. Gently pull bulbs from soil and lay on ground to cure for 2-3 weeks in a warm, dry, well-ventilated location (avoid direct sunlight which can scald skin). Once fully cured, trim roots and tops, leaving 1-inch stem. Store in cool (45-50°F), dry location with good air circulation; properly cured Walla Walla onions can store 2-3 months.

Fun Facts

🌱 Walla Walla onions are named after the Walla Walla Valley in Washington state, where they were developed in the 1880s from seeds brought by Italian immigrants, and have been the official state vegetable of Washington since 2007.
🌱 These onions are so sweet they can be eaten like apples raw, and some people eat them whole like an apple—a testament to their exceptionally low pungency compared to other onion varieties.
🌱 The sweetness of Walla Walla onions is due to their high sugar content and low sulfur levels; the sulfur compounds are what make other onions tear-producing and pungent, so these onions won't make you cry.

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