There's a 4th tier flower that is generous on sell-back too. I want to say it's either Roseacea Fern or Jalapa Tree. However, Blue Rose Rosebushes are much easier to obtain early in the game. You're right, Zia - I have both Roseacea and Jalapa Tree self-spawning a couple of plants a week, but I also have 600K coins and get over 10K in interest each day.

Guess it's time to build out the house and buy some furniture.