Sweet Onion
Sierra Blanca is a hybrid F1 onion that produces impressively large, mild white bulbs ready to harvest in 109 days from transplants. Hardy across zones 3 through 10, this variety thrives in cool to warm climates and handles the transition from seedling to mature bulb with reliable vigor. Its compact growth habit and frost tolerance make it a dependable choice for gardeners working with transplants, delivering consistent results whether you're in a northern garden or a milder region.
—
Moderate
3-10
?in H x ?in W
Annual
Moderate
Hover over chart points for details
Big, mild white onions with genuine storage potential and the ability to thrive across a remarkably wide hardiness range. The mild flavor makes these onions approachable for fresh eating, and their size means you get substantial yields from a modest plant footprint. The frost-hardy nature sets them apart from tender varieties, giving you flexibility in spring planting timing.
Sierra Blanca onions are excellent fresh eating thanks to their mild, sweet character. The large white bulbs are ideal for slicing into salads, grilling whole or in wedges, or roasting until caramelized. Their substantial size also makes them practical for long-term storage, so you can preserve your harvest through winter months for cooking throughout the season.
Sow seeds indoors 6 to 8 weeks before your last frost date in long- and intermediate-day growing regions. Fill 128-cell trays with seed-starting mix, sow 1 seed per cell, and cover with 1/4 inch of soil. Keep soil temperatures between 50 and 70 degrees Fahrenheit for germination. Seedlings develop tall, thin foliage that may look unruly; you can clip tops back to 5 inches at transplanting time to encourage sturdier growth without harming the plants.
Transplant seedlings outdoors 4 inches apart in rows spaced 12 to 18 inches apart. Plant in full sun with fertile, well-drained soil. In heavier clay soils, use raised beds or raised rows to promote drainage. The frost-hardy nature of this hybrid allows transplanting earlier in the season than tender varieties.
Sierra Blanca onions reach maturity in 109 days from transplant. Harvest when the bulbs have reached full size and the foliage begins to brown and fall over naturally, signaling the end of the growing season. Once mature, allow tops to dry before harvest. Clip off the dried tops and roots before storage to prepare bulbs for long-term keeping.
Enter your ZIP code to see a personalized growing calendar for this plant.