What kind of citrus am I?

One of the cool things about moving to Florida last month was finding I had my very own well-grown citrus tree in the back yard. But what kind of citrus tree is it? The tree was loaded with fruit, but they were all still immature and green. The lawn guy who came to give me a clean-up estimate said that is was an orange tree. I was pretty excited about that.

But then my next door neighbor told me he thought it was a lemon tree. He said that he had helped the previous owner trim the tree one time, and he remembered that it had thorns. And he said that lemon trees have thorns and orange trees don't. So is it a lemon tree?

I checked, and sure enough it does have thorns. Ouch, not so easy to harvest the fruit. And the fruit is beginning to ripen, and it appeared that the fruit WAS turning yellow.

But I checked again today, and found that some of the fruit have gone beyond yellow and begun to turn a strong orange color. So is it an orange? One fruit had turned a very orange color, and had fallen from the tree, so I thought perhaps it was ripe, and brought it inside and cut it in half.

It was quite orange on the inside too. It sure *looked* like an orange and not a lemon, thorns or no. So I gave it a taste. Euwwwww. Talk about SOUR. This thing was the most sour citrus fruit I'd ever tasted! But it didn't taste like a lemon either. The taste was .... indescribable. Just sour.

Well, could it still be an orange? The lawn guy said that orange trees need to be fertilized with lime in the spring to grow sweet fruit, and my tree was not fertilized this year because the house had been vacant for a year before I moved in. The lawn guy says he'll fertilize for me this coming spring.

But in the meantime, just what sort of fruit do I actually have? And is there anything I can *do* with the dozens and dozens and dozens of fruit ripening on the tree?