Question
I started a grapefruit tree from a seed. the tree is approx 2 foot tall. what is the proper fertilizer and how often should I fertilize. I have it in a 2'x2' round pot. I live in Ohio so it has to be indoors during winter. I thought I killed it last fall because I got hit by frost and last all its leaves so I didnt water it during the winter. Set it outside in the spring and the tree bounced back and looks better than ever has. Looking for proper care for a tree of this type.  Thanks for your help.  

Answer
Fertilize with 10-10-10 in spring and summer. You may have to transplant into a larger pot next spring.

You can either store it dry (minimal water) in a dark, cold basement (above freezing but as cool as possible) like you did list time, or you can keep it actively growing.

If latter, then I recommend putting it in front of a sunny southern facing window and supplement with artificial light (flourescent light bulbs hung suspended a few inches above the top of the plant).