Just an idea, but maybe you could add different types of soil, maybe there could also be a chance (like a 0.01% chance) for a flower to grow as a rare variant, maybe taking multiple clicks (like 5 clicks for a rare daisy and 100 clicks for a rare sunflower, bc of autoclickers) or an extra flower an ability. (like a cactus and gardening gloves [you can only buy 5 and they 1.5x the crop value} or smth similar)
Sorry for the amount of text :)