Sierra Blanca Onion is a hybrid, intermediate-day onion with bright white, snowy scales that makes it a great variety for the home gardener and small-scale market farmer. This white onion variety consistency produces huge globe-shaped onions that are in the jumbo to colossal size range.
Sierra Blanca Onion can be direct-seeded or transplanted, although we recommend transplanting. For direct-seeding, plant seeds 2″ apart along the row with a row spacing of 24″. Once seedlings emerge, thin seedlings to a 6″ plant spacing along the row. Plethora Onion seeds can be planted with our Hoss Garden Seeder. We recommend using a #1 seed plate and modifying the hole size slightly to accommodate the onion variety being planted. For denser plantings, more holes may need to be drilled to accommodate a thicker spacing.
For transplanting, plant one seed per cell in our heavy-duty seed starting trays. Once the green stems reach 6-8″ in length and/or they can be easily pulled from the seed trays, the transplants are ready to go in the ground. Transplant onions 4-6″ apart along the row with a row spacing of 24″. If drip irrigation is used, onions may be planted on double rows with drip irrigation in the middle. We suggest burying the drip tape 3-4″ deep and planting on both sides of the tape.
Onions are heavy feeders and will require significant nutrient inputs throughout their lifespan. We recommend feeding them with our 20-20-20 and Ammonium Sulfate fertilizers. Fertilize with 20-20-20 shortly after transplanting. The phosphorous and potassium in the 20-20-20 fertilizer will help to promote solid root development, while the nitrogen will promote vegetative growth. Once transplants are established, we recommend side-dressing or injecting with our Ammonium Sulfate fertilizer. Side dress or inject 1 cup per 20 feet of linear row every 3-4 weeks after transplanting.
Sierra Blanca Onion Planting Information
Planting Method: transplant
When to Plant: early spring
Planting Depth: 1/4″
Seed Spacing: 4″
Row Spacing: 12-18″
Days to Maturity: 110
Disease Resistance: Pink Root Rot
Onion Planting Guide
Select an onion variety based on your geographical location. In many cases, intermediate-day varieties can be grown in southern long-day regions and northern short-day regions.
- Plant in fall and overwinter for a spring harvest
- Start the bulbing process when day length reaches 10-12 hours
- Plant in late winter for an early summer harvest
- Start the bulbing process when day length reaches 12-14 hours
- Plant in spring for a mid-summer harvest
- Start the bulbing process when day length reaches 14-16 hours
– Plant in spring for a mid-summer harvest
– Start bulbing when day length reaches 14-16 hours
– Plant in late winter for an early summer harvest
– Start bulbing when day length reaches 12-14 hours
– Plant in fall if temps are rarely below 20F
– Plant in late winter if temps are frequently below 20F
– Start bulbing when day length reaches 10-12 hours
Franco (verified owner) –
I seem to consistently have problems with my onions. I think its because not enough water and too much week pressure, but not sure . However this variety was my best effort ever. I had many baseball to softball size onions. I was about to give up but will keep trying and will try these again. This season was my only season and to grow these and my first season to have consistent onions.