How to Grow Walla Walla Sweet Onion (Red Variety)
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Walla Walla Sweet Onion (Red Variety)
Allium cepa var. cepa
vegetableWalla Walla onions are a long-day variety known for their exceptional sweetness and mild flavor, with the red variety displaying deep burgundy skin and pale pink interior rings. These large, tender onions have high water content and low sulfur levels, making them perfect for fresh eating and cooking. The red variety offers both the sweet flavor profile and an appealing visual presentation.
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Example Walla Walla Sweet Onion (Red Variety) timeline · Pittsburgh, PA (Zone 6b)
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Plant Walla Walla Sweet Onion (Red Variety)
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 Walla Walla Sweet Onion (Red Variety)
Around Aug 15≈ 120 days after planting
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Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 3-9; requires cool winters for proper bulb development
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Establishment (Transplant/Set)
2-3 weeksNewly planted onion sets or transplants developing root systems and first true leaves
Keep soil consistently moist; protect from harsh sun if recently transplanted; avoid high nitrogen early on
Vegetative Growth
4-8 weeksLush green foliage developing; plant building leaf surface area to support bulb formation
Maintain consistent watering and light feeding; thin to proper spacing if needed; mulch to retain moisture and regulate soil temperature
Bulb Initiation & Development
6-10 weeksFoliage continues growing as underground bulb begins to swell; visible thickening at base of plant
Long days trigger bulb formation; continue regular watering and moderate fertilizing; ensure adequate sun exposure
Maturation & Dormancy
2-4 weeksFoliage yellows and falls over naturally; outer skin papery and deep red; bulb becomes firm and dense
Reduce watering significantly; allow foliage to naturally senesce; do not force over; ensure good air circulation to prevent rot
Harvest & Curing
Harvest over 1-2 weeks; curing takes 2-4 weeksOnions pulled from ground with dried foliage still attached; bulbs laid to cure in cool, dry location
Harvest when 50-70% of tops have fallen over; cure in warm (75-80°F), dry, well-ventilated area for 2-4 weeks; trim roots and foliage once fully cured
Common Pests
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Row covers during early growth; remove affected plants; maintain clean garden debris; rotate crops; nematodes (beneficial)
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Strong water spray to dislodge; insecticidal soap; spinosad; ensure adequate spacing for air flow
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Plant disease-resistant varieties; ensure excellent drainage; avoid overhead watering; remove infected bulbs immediately; sanitize tools
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Improve air circulation; avoid overhead watering; apply sulfur fungicide; plant in well-draining location
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Cardboard collar barriers around transplants; Bacillus thuringiensis (Bt); remove plant debris; hand-pick if visible
Uses
Fresh eating and salads
CulinaryWalla Walla reds are exceptionally sweet and mild with crisp texture, perfect for raw consumption in salads, salsas, and sandwiches. Their natural sugars and low pungency make them ideal for fresh applications where raw onion flavor is desired. [source]
Grilling and caramelizing
CulinaryThe high sugar content in Walla Walla reds makes them excellent for caramelizing, grilling, and roasting, developing deep sweetness and complex flavors. These onions naturally sweeten when cooked, creating a rich umami quality. [source]
Preserving and pickling
CulinaryTheir mild flavor and firm texture make Walla Walla reds suitable for pickling, making relishes, and creating canned condiments. The red variety adds visual appeal to preserved preparations. [source]
Natural dye production
HouseholdThe deep red skins of red Walla Walla onions can be used to create natural dyes for textiles, producing warm red and rust tones. The papery outer skin is especially rich in color compounds. [source]
Nutritional and antioxidant benefits
MedicinalWalla Walla onions contain quercetin and other antioxidants, particularly abundant in the red variety. These compounds have been studied for anti-inflammatory and cardiovascular health benefits. [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 50-70% of foliage has naturally fallen over (typically June-July in most zones). Gently lift bulbs with a fork to avoid bruising. Allow to dry in field for 1-2 days if weather is dry, then move to cure. For storage, cure in a warm (75-80°F), dry, well-ventilated location for 2-4 weeks until outer skin is papery and foliage is completely dry. Trim roots to ½ inch and remove dried foliage. Store in cool (50-55°F), dry area; these sweet onions have lower storage life (3-5 months) compared to storage onions due to high water content. Best used fresh within 2-3 months.
Fun Facts
- 🌱 Walla Walla Sweet Onions are named after Walla Walla County in Washington State, where they were popularized in the early 1900s after seeds from Peru were brought back by a Spanish soldier; they're now the official state vegetable of Washington.
- 🌱 The exceptional sweetness of Walla Walla onions comes from their low sulfur content (less than 0.5%), while regular onions contain 1-2% sulfur, which is why they won't make you cry as much when cutting them raw.
- 🌱 Walla Walla onions are a long-day variety, requiring 14-16 hours of daylight to trigger bulb formation, which is why they must be grown in northern climates or as a winter crop in warmer zones—planting them as a spring crop in zones 8+ requires special short-day varieties instead.
Gardening Terms
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