I've grown onions from seed for many years. I start them inside and when they come up, put them under good plant lights. I am in Zone 4a so direct seeding doesn't work, as they are a day length sensitive plant. So much so, that with the gloomy weather we had here in New England last year, my onion crops were a failure. But I have hopes for this year! They will be in a different area, so we will see.