As a child I grew a lemon and an orange tree from seed. After a decade without fruit my mom told me something about part of the tree needing to be cut. Now I realize she was talking about grafting.

I recently brought home a lemon tree from a nursery, with hopes of fulfilling my childhood fantasy of having a fruit bearing tree. While researching pruning I grew concerned after I couldn't find a graft line. The tree does however have quite a large scar where it looks like the trunk would have been growing.

Is it possible the graft was unsuccessful? Can anyone give me some insight into what may have happened? Will the tree produce fruit? How can I identify suckers?

Sorry for asking so many questions. I want to know if I should dig it up and exchange it at the nursery.

I have dug down a little to show the top roots for the photo to assure anyone I haven't planted it too deeply or hidden the graft line.