If you let a fruit sit over time it will eventually rot, but luckily that's not how it works. Animal Crossing: New Horizons. You don't have to worry about letting the fruit sit and rotting. You get rotten fruit in a different way.
Rotten Fruit appeared in New Leaf, where if players could plant and grow a Perfect Tree, they could get Rotten Fruit. It only happened at the end of the tree's life. You could shake the tree seven times, with three perfect fruits with each shake. In the last jolt, the tree would produce two perfect fruits and one rotten one.
You couldn't do too much with the rotten fruit. Could sell it if you have bells hurt, or provide it to one of your residents who was looking for fruit in your home. They wouldn't be too happy to receive a rotten one, but it had no repercussions. Leaving rotten fruit on the ground was also a great way to attract ants.
For now, we are not sure how to maintain and create a perfect fruit. Even in past Animal Crossing games weren't very clear about the process. However, when you can get one, prepare for a rotten fruit at the end of the tree's life.
