I was practicing with modeling a leaf using a image reference. Everything went fine and I finished modeling my leaf, but I wanted to make it more realistic (I'll add textures later), I saw lots of people using the Subdivision Surface modifier but it doesn't work for me.

My model:
![My 3d Model](https://i.stack.imgur.com/4zR15.png)

My model when I add the Subdivision Surface modifier
![My 3d Model when i add subdivision surface modifier](https://i.stack.imgur.com/6GXjG.png)

![Finished Leaf](https://i.stack.imgur.com/nXpMC.png)