Merge Plants: Zombie Defense Android Game Description:
There are areas with fertile soil at the player's disposal, and hordes of different types of zombies cross these areas. In order not to let these mobs to reach the target you can plant different plants, which  play the role of defense towers in the game.
Tower-plants are upgraded by merging - by joining two identical plants, you can get another more advanced and powerful. The range of available plants and abilities is quite good. Also, you can move them and open up new areas with soil.