How to Grow Onion Walla Walla

Onion Walla Walla

Allium cepa var. cepa

vegetable

Walla Walla onions are a sweet, mild variety of bulbing onion known for their large size and exceptional flavor. Unlike most onions, they have a naturally low sulfur content, making them sweet enough to eat raw. These long-day onions are prized by gardeners for their tender, juicy bulbs that store moderately well.

Growing Conditions

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Sun: Full sun, 8+ hours daily (long-day varieties need extended daylight)

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Water: Consistent moisture during growing season (1-1.5 inches weekly); reduce watering as bulbs mature and tops yellow; keep soil evenly moist but not waterlogged

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Spacing: 4 inches

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Days to maturity: 120-150 days from transplant

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Planting depth: Plant sets 1 inch deep; seed indoors 6-8 weeks before planting

Soil

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

pH: 6.0-6.8

Amendments:

Compost or aged manure Balanced fertilizer (10-10-10) Boron (if deficient) Calcium (gypsum if needed)

Growing Zones

Find your zone →

Thrives in zones 3-9, particularly suited to cooler climates (zones 4-7)

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

Growth Stages

Seedling

2-3 weeks

Tiny green shoots emerge from seeds or sets; thin root system developing

Keep soil consistently moist but not waterlogged; provide bright indirect light if grown indoors; thin seedlings to proper spacing once established

Vegetative/Foliage Growth

4-6 weeks

Long, cylindrical green leaves emerge and grow upward; minimal bulb development underground

Maintain consistent watering and full sun exposure; apply balanced fertilizer every 3-4 weeks; ensure good air circulation to prevent disease; mulch lightly to conserve moisture

Bulb Development

6-8 weeks

Bulb begins swelling underground as day length increases; leaves continue growing tall and thick

Continue regular watering as bulb expansion is critical; apply phosphorus-rich fertilizer to encourage bulb development; monitor for pests and diseases; keep area weed-free

Maturation

3-4 weeks

Bulb reaches full size; leaves begin yellowing and falling over (lodge); outer skin papery layers develop

Reduce watering when tops begin to yellow; stop fertilizing; do not water during final 2-3 weeks to allow skin to cure and harden; avoid disturbing bulbs

Harvest & Cure

Harvest 2-3 weeks, cure 2-3 weeks

Bulbs pulled from ground when 50% of tops have fallen over; outer skin dry and papery

Pull bulbs and cure in a warm, dry location with good air circulation for 2-3 weeks before storage; remove excess soil gently; store in cool, dry place with low humidity

Companion Planting

Plan your garden →

Plant with:

Carrot Beet Strawberry Lettuce Cabbage Chamomile Dill Parsley

Avoid planting near:

Bean Pea Asparagus Sage Garlic Other onion varieties

Common Pests

Use row covers; apply spinosad or neem oil; rotate crops; remove and destroy infested plants; use beneficial nematodes
Spray with insecticidal soap or neem oil; maintain proper spacing for air circulation; remove heavily infested plants
Use fine mesh row covers; avoid planting near compost or manure; remove infected sets; plant resistant varieties
Apply diatomaceous earth; use cardboard collars around young transplants; handpick; maintain clean cultivation
Spray with water; use insecticidal soap; encourage beneficial insects like ladybugs; neem oil application

Uses

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Fresh eating and mild cooking

Culinary

Walla Walla onions are ideal for eating raw in salads, salsas, and sandwiches due to their exceptional sweetness. They can be grilled, roasted, or caramelized to bring out even more natural sweetness. [source]

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Pesto and spreads

Culinary

The mild, sweet flavor makes Walla Walla onions excellent for creamy spreads, compound butters, and onion pesto that highlight their natural flavor without the sharpness of standard onion varieties. [source]

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Natural dye production

Household

Walla Walla onion skins and flesh can be used to create natural dyes for textiles, producing warm yellow and gold tones on fabric. [source]

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Traditional wellness support

Medicinal

Like all onions, Walla Walla contains quercetin and other antioxidants traditionally used to support immune function and cardiovascular health. [source]

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Pollinator and beneficial insect habitat

Wildlife

Allowing a few Walla Walla onions to bolt and flower produces attractive purple blooms that attract bees, butterflies, and other beneficial pollinators. [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 50% of the tops have fallen over and turned brown, typically late July to early August in most regions. Carefully pull bulbs from the ground and cure them in a warm, well-ventilated location (70-85°F) for 2-3 weeks until the outer skin is papery dry. Trim roots and dried tops once fully cured. Store in a cool, dry place with good air circulation; Walla Walla onions have lower storage longevity (2-3 months) compared to storage varieties due to high moisture and sugar content.

Fun Facts

🌱 Walla Walla onions are named after Walla Walla County in Washington State, where they were first grown commercially and remain a signature crop. The region's ideal climate and soil conditions produce their legendary mild, sweet flavor.
🌱 Unlike most onions, Walla Walla onions contain significantly lower levels of sulfur compounds, which is why they taste noticeably sweeter and less tear-inducing when sliced—a trait controlled by genetics rather than soil.
🌱 These are 'long-day' onions that require 14-16 hours of daylight to form bulbs, making them perfectly suited to northern regions with long summer days. They perform poorly in short-day climates where they may never bulb properly.

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