I think what really matters is the Green Thumb trait, and/or Loves The Outdoors. You can easily get to level 3 or higher in a single day, but you need the Green Thumb trait in Immortal Dynasties, so that you can revive and replant Death Flowers. (well, it is not exactly necessary, but it is very helpful)
My suggestions would be the same as everyone else. Zelda is the best in Sunset Valley, I think. She has the trait, and she is a Young Adult.