How to Grow Candy Onion
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Candy Onion
Allium cepa var. cepa
vegetableCandy onions are a group of sweet onion varieties known for their exceptionally high sugar content and mild flavor. These large, globe-shaped onions are ideal for fresh eating, grilling, and caramelizing due to their natural sweetness. They are less pungent than storage onions and contain up to 12% sugar by weight.
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Example Candy Onion timeline · Pittsburgh, PA (Zone 6b)
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Plant Candy 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 Candy Onion
Around Jul 26≈ 100 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Candy Onion dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Zones 4-9; warmth and long growing seasons favor sweetness development
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Seedling
3-4 weeksThin, grass-like green shoots emerge from soil. Seedlings develop their first true leaves and root system.
Keep soil consistently moist. Thin seedlings to proper spacing once they reach 2-3 inches tall. Start seeds indoors 4-6 weeks before transplant date.
Vegetative Growth
6-8 weeksPlants develop multiple green leaf blades and establish strong root systems. Visible bulb formation begins underground.
Maintain consistent watering and full sun exposure. Apply balanced fertilizer every 3-4 weeks. Remove any flower stalks (bolting). Mulch to retain soil moisture.
Bulb Development
4-6 weeksThe underground bulb begins swelling noticeably. Foliage becomes more robust and may reach 12-18 inches tall.
Continue regular watering but avoid excessive nitrogen, which promotes leaf growth over bulb size. Ensure adequate potassium and phosphorus for bulb development.
Maturation
2-3 weeksBulbs reach full size. Foliage begins to yellow and weaken. Outer papery layers develop.
Gradually reduce watering in the final 2-3 weeks to concentrate sugars and allow papery skin to form. Stop fertilizing.
Harvest Ready
At harvestApproximately 50% of tops have fallen over and dried. Bulbs have papery, thin outer skin. Necks are dry and thin.
Stop watering entirely 1 week before harvest. Cure harvested onions in a warm, dry, well-ventilated area for 2-3 weeks before storage.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Spray with neem oil or insecticidal soap; encourage beneficial insects; maintain consistent watering to reduce thrips populations; use reflective mulches
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Use row covers on young plants; apply beneficial nematodes to soil; practice crop rotation; remove affected bulbs immediately
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Ensure excellent drainage; avoid overhead watering; sterilize tools between plants; destroy infected bulbs; practice 3-year crop rotation
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Improve air circulation; avoid overhead irrigation; apply copper fungicide at first signs; remove affected leaves
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Hand-pick in early morning; use beetle traps; apply spinosad if infestation is severe; encourage natural predators
Uses
Fresh eating and salads
CulinaryCandy onions are mild and naturally sweet, making them ideal for eating raw in salads, sandwiches, and slaws. Their sweetness shines when consumed fresh without cooking. [source]
Grilling and caramelizing
CulinaryHigh sugar content caramelizes beautifully when grilled or sautéed, creating deep, complex sweetness. Perfect for grilled onion steaks, burgers, and slow-cooked caramelized onion jam. [source]
Roasting and baking
CulinaryTheir natural sweetness intensifies when roasted whole or halved in the oven, becoming creamy and deeply flavored. Excellent as a side dish or ingredient in gratins and casseroles. [source]
Pickling and preservation
HouseholdCandy onions can be pickled with vinegar, spices, and sugar to create sweet-tangy condiments. Their mild flavor provides a pleasant balance to acidic pickling brines. [source]
Nutritional and health benefits
MedicinalOnions contain quercetin and other antioxidants associated with anti-inflammatory and cardiovascular benefits. They are a good source of vitamin C, fiber, and prebiotic compounds that support gut health. [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 dried, typically in late summer. Carefully dig bulbs to avoid bruising. Cure in a warm (70-75°F), dry, well-ventilated location for 2-3 weeks to develop papery skin and improve storage. Store in a cool, dry place with good air circulation. Candy onions have shorter storage life (2-3 months) compared to storage onion varieties due to their higher moisture and sugar content.
Fun Facts
- 🌱 Candy onions like Walla Walla and Vidalia are so sweet that some people eat them like apples; their high sugar content (up to 12%) makes them uniquely suited for this.
- 🌱 The sweetness of candy onions is directly tied to their growing environment—longer daylight hours and warm temperatures during growth increase sugar accumulation, which is why they thrive in specific regions.
- 🌱 Candy onions contain significantly less sulfur than storage onions, which is why they lack the harsh, tear-inducing bite and instead have a mild, pleasant flavor both raw and cooked.
Gardening Terms
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