If your Dad lives in zone 7, it will never survive the winter short of your building a heated greenhouse over it, unfortunately. I think lemons are rated maybe zone 8B or 9a? Yes, most all citrus from seed is very thorny. That's normal.

What kind of seed did he plant? Most lemons do come true-to-type.

Keep in mind these plants need to get very large before they can bear fruit -- maybe 10-14 feet tall or more before the growth gets out of its juvenile form and can begin to bloom.

They do make an interesting potted plant though.

Yours looks like it needs a bigger pot so the roots can stretch a bit. Make sure it does not sit in water after watering or sit in full sun. These plants really like perfect drainage. Full sun can cook the roots in the pot.

Good luck!

This post was edited by dave_in_nova on Sat, Aug 31, 13 at 18:47

Lemons need much more heat than oranges, or rather they can stand much less cold. Take Dave's advice, give it more space (bigger pot), and water it. Curled leaves means the tree is dry.