The questions in the title... What foliage do you use the most?
I use grassland biome a lot in my zoos so I use the Bur Oak tree as well as some maple, acacia thorn and japanese cherry trees.
In terms of plants, I love AD's fern and other plants in Sophie's temperate forest scenery pack...
I don't have MM so I don't know about underwater foliage, but you guys can elaborate! 