While I will start some onions from seed in the spring, I also like to start some in late summer and overwinter them.
Here are my growing tips for onion seeds:
- 1. You can plant the seeds outdoors but keep in mind that onions prefer temperatures between 50 and 75 °F to germinate. I typically start the seeds indoors under my T5 grow lights. When they are about 3 inches tall, they are ready to be transplanted
2. I will transplant onion seedlings in mid spring (or up to 5 weeks before the last spring frost) under cover or late summer/early fall. When I overwinter them, I put some leaves around the seedlings to give some insulation and cover my pvc hoops with fabric and plastic once we are expecting frost. I vent the covers once the temperature gets around 50°F.
3. While I find onions grown from seed to be hardy, you can always add a balance plant food if you need.
If you missed my post on how to Sow and Grow Onion Sets, then just click on the link.