Millet and Laaz, thank-you very much for your feedback. As I noted, this is a new venture for me.
Maybe the rootstock isn't lemon. The source is new growth from the base of an existing tree that is producing a good and tasty crop of normal (valencia-like) oranges. When I 'inherited' this tree, it was full of lemon-like fruit. Their surface was somewhat rough - almost like big warts. The fruits were about 8-10 cm long and slightly smaller diameter. I was told by several locals that it was a wild lemon native to this region of Baja California. They looked somewhat like citrus macrophylla
. I noted a single branch with an orange on it and concluded the tree was probably originally an orange grafted onto the 'lemon' rootstock. The tree had probably not had any attention for a decade or more and I assumed most of the growth was from the original rootstock. Over time I removed all of the 'lemon' bearing branches and now seem to have a magnificent orange bush. Now, unfortunately, I have no fruit to identify the rootstock.
Given that this bush already produces good oranges, do you think that the new growth from the rootstock of this bush may be a good source of new rootstock?