How to Grow Sweet White Onions

Onions are related to garlic, chives and shallots.

Sweet white onion varieties do not store well for long periods and need to be eaten shortly after harvest instead of being dried. For this reason, you cannot grow them from onion sets, which are small, dormant, dry onion bulbs. Grow sweet onions from seeds or from transplants. Transplants are small onion plants that are still vegetative, not dormant like onion sets, and are the faster-growing option.

Things You'll Need

• Tiller or cultivator
• Sweet white onion transplants or seeds
• Starter-fertilizer solution
• 10-10-10 fertilizer
• Hoe
• Soilless mix (optional)
• Individual cell packs (optional)
• Plant light (optional)

Instructions

Growing From Transplants

1. Till or cultivate fertile, well-drained soil in early spring, ideally late March or early April. Cool temperatures encourage leaf growth, leading to larger bulbs at harvest.

2. Plant transplants 1 inch deep and 5 inches apart. Space rows 16 inches apart to allow space for large bulbs.

3. Fertilize newly planted transplants with a starter-fertilizer liquid solution. Use 1 cup of fertilizer per plant.

4. Weed or hoe around growing onions to keep weeds at bay. Side-dress with 10-10-10 fertilizer five weeks after planting and water often enough to provide growing onions with a total of 1 inch of water per week, including rain.

Growing From Seed

1. Sow sweet white onion seeds in the autumn in a soilless mix in individual cell packs. Cover the seeds with 1/4 inch of the soilless mixture.

2. Water and keep the seeds consistently moist. Place the seeds in full sun or under a plant light in room temperature (72 degrees Fahrenheit) conditions. The seeds will germinate in about two weeks.

3. Cultivate the seedlings in controlled conditions until they reach about 1/4 inch in diameter. This should occur in late winter after an autumn planting.

4. Transplant the seedlings to the garden, following the directions for growing from transplants.

Tips & Warnings

• You can plant onions 2 inches apart and harvest some of them for green onions, leaving the remainder to grow into large bulbs.

References

• Alabama Cooperative Extension System: Home Gardening: Growing Onions
• University of Illinois Extension: Onion