Etrog Orla

A friend just gave me a new esrog tree that he is growing from seeds. This is my first real orla experience. Orla, for those who don't know, is one of the few farming mitzvas that is kept in both Israel and outside of Israel. During the first 3 years of growth ou are not allowed to derive any pleasure from the fruit. In the 4th year (during the time of the bais hamikdash) you are supposed to take it to Jerusalem and eat it there. Most of the rules are the same as maaser sheni. Today, since we don't take it to Jerusalem, we redeem it on a coin and then destroy the coin. You used to be able to redeem it on a coing and then spend the money in Jerusalem, but we don't do that today for some reason having to do with Jerusalem having been destroyed and not officially rebuilt yet. I'm sure my chavrussa will be quick to correct me on the Zionist progoganda reason (having to do with tuma or something) right after he reads this.
In any case, I can use the esrog for a mitzva in 3 years after tu bshvat (rosh hashana for the trees).