Lemon Tree

The Lemon tree, is considered, the hardest to get decoration in game, has it can only be won by a Mystery Box. It has a chance of 10% of apearing in a Mystery Box.

Simpsons Wiki Description
The tree was planted over a hundred years ago, when Springfield was founded by  Jebediah Springfield and  Shelbyville by  Shelbyville Manhattan. Because it was a "sweet moment" in the town's history, the Springfield townspeople chose to plant a lemon tree, because lemons were the sweetest fruit available at the time. The tree was very near the point where Jebediah and Shelbyville parted ways, so it ended up being very close to the boundary between the towns of Springfield and Shelbyville.


 * Read the full article here at Simpsons Wiki.

Trivia

 * You can't sell the Lemon tree.
 * You can get it for free, if you get it from the free Mystery Box, from the dayly bonus.
 * You used to be able to steal other peoples Lemon trees, a reference to the episode where the tree was stolen.