We planted our lemon tree in Fall of 2006 as a 24" box. It has grown to a height of 20 feet plus and has produced a major crop every year but one. In that year we had a major freeze and we removed over a hundred pounds of frozen fruit, we have had a full crop every year since.
Our tree is positioned in an alcove that faces south.
We wrap the tree every winter on the south face of the tree and leave a vent at the top so the heat build up from the wrap during the day can vent.
We hand fertilize on four sides of the tree in most years and have general fertilizer tank that we fill twice a year in the spring and fall.