Re: Why is my orange tree turning into a lemon tree?
You can keep the lemon, but if it is the typical rough lemon used for rootstocks it may not be that desirable, or at least there may be better varieties that you could add by grafting. If the lemon part of the tree is comming up from near the root, it probably was the rootstock. If you leave that part unrestrained, it may dominate the tree taking away some of the energy that would go to the oranges.
The small fruit may be due to a variety of things, the lemon taking away some of the energy, lack of water and lack of fertilizer could also contribute. The tree might also need a dose of trace minerals if it has not been included in fertilizers.
If you are interested in grafting, living in CA you can get grafting wood from UC Davis I believe. T-bud grafting is really simple-- I had over 60% success my first time this past summer putting over 40 buds on the 5 trees in my backyard. My lisbon lemon now has at least 10 varieties on it-- oranges, mandarins, satsumas, meyer lemon, grapefruits.