Recently I acquired a couple larger citrus trees that were at home depot and were on clearance since they were neglected. They are the larger trunk type where the graft is a foot or so from the soil level and about an inch in diameter. I was curious to know if this is accomplished by simply having an older rootstock that you graft higher on or is it simply a choice of where to graft with the same young rootstock? I am trying to learn up on grafting before I start to try my hand at it this year. I like the look of the taller tree type and wanted to see how it is accomplished. Any specifics on thickness of rootstock to graft to would also be helpful.
Thanks!

The height of the graft is a matter of choice--some say that the higher you graft the more characteristics of the rootstock (like cold tolerance), but the down side is that it becomes more difficult to bank the graft in case of cold.

It is unlikely the tree was 1 inch in diameter when it was grafted, the preferred size for grafting is about 1/4 to 3/8 inch.

Grafting high on thin stocks requires a bit of extra care and staking, in case the rootstock gets snapped. If you want to graft high to get an instant bushy tree, try a scion peice with several buds, and dont let one become the main shoot. If you are working on larger stocks, one reason to graft or bud high, is to better size match the available scion material to the stock. This will leave less of a flat stump to heal over at the graft union.