Yellow Sweet Spanish Onion Guide
Onions grow well in temperatures between 55°F-75°F. They do ok in containers and gardens. Bank on Seeds recommends transplanting.
If Direct Seeding
- Direct seed outside 4 weeks after last frost date; or
- Direct seed into a container 10 inches deep and 16 inches wide anytime of the year. It can be placed outside when the temperature is between 55°F-75°F; or
Begin the growing season early and start the onion seeds indoors in pods 6-8 weeks before the last frost date; germination is best between 65°F-75°F. It can be transplanted outside 10 weeks later.
Sow the seeds ¼ inch-deep, 4 inches apart with rows spaced 12 inches in between. Germination will take 10-20 days. Thin to 12 inches apart when the seedlings start competing for space or light.
Onions need well-draining, fertile soil. They also love full sun and will need as much light as you can give it. Water every week in the first 4 weeks. Once established, water regularly and consistently since the onion roots are shallow. Check the top 1-2 inches and if dry, then water the soil.
Onions are heavy feeders and like fertilizer throughout their growth. Option to add compost to soil as well as a regular feeding of compost tea or 10-10-10 fertilizer.
Spanish sweet onion is full grown (mature) in 90-110 days. Cut the sprigs when they are young to use as green onions or wait until full maturity to use the full globe. The tops of the foliage will begin to slump over and wither – at this point loosen the soil around the onion to let it dry then gently pull the bulbs out when they feel dry and the skin is tight.
Onion flies, leaf miner - hand pick off, neem oil, insecticidal spray, plant collar or row covers
Allium rot, neck rot, rust - maintain 3-year crop rotation, check for bugs often and manually remove, neem oil, row cover during early growth
*Companion plant onions with broccoli, kale, cabbage, lettuce, tomatoes, peppers, and strawberries. Avoid planting with asparagus, beans, peas, and sage. *