I basically have trees in every single place they will grow that doesn't block vision of paths, and I also have flowers everywhere, so... a lotta both XD
My town's definitely filled with flowers in almost every corner. I only have 4/5 small forest areas and a scatter of trees everywhere else. Flowers are also easier to use for design and color than trees though so that's mainly why.
It's probably easier to have more flowers too because they don't take up as much space. A lot of towns I've visited are covered entirely in flowers. I hope I can get my town there some day.