Why an Etrog at Sukkot?

Torah says to use fruit, branches, boughs, & willows in celebrating Sukkot, and tradition names specific species for each. The fruit is said to be an etrog, also known as citron, but this particular fruit wasn't grown in Israel or Sinai until 1000 years or more after the Torah was given to Moses, so it seems unlikely in the extreme that an etrog (and only an etrog) was the original intent. I doubt that God intended it to be limited to any particular variety of fruit at all. Since Sukkot is a harvest festival (the third on God's calendar), He probably mean *any* fruit that ripens at or just before the holiday.

There's no reason you can't use an etrog with your lulav, but it's not absolutely required by the written Torah. My advice is to stick with tradition if you find it especially meaningful, or use whatever fruit is naturally ripe at this time of year in your locale. Whatever you choose, just make it the best you can find and can reasonably afford.