We will be working on our Onion Patch this week. We have 2 varieties we will be planting. Both are Intermediate Day Onions which grow well in Middle TN. We have "Candy" and "Red Candy Apple".
My Granddaddy is a pro at growing onions. He would have them get as big as a softball every year. He told me that you need to get them in the groud by February 15. Keep them weeded. Apply a high Nitrogen fertilizer, every 2 weeks in between the rows. It is true too, we tried his methods last year and had the best onions there ever was.
We order our onions in bulk. The key is ordering from a trusted supplier and picking the right onion for your area. Middle TN is an Intermediate Day Onion area. But if you live up North, you will need a Long Day Onion. If you live further South, then you will need a Short Day Onion. Beware if you go to the store and get a bunch of onions -- they may not be the right type for your area.