Here is the full list of all 9 Reach for the Sun achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
Purchased all four plants.
Purchased all plants and all upgrades.
Fruited a flower without growing any extra leaves.
Grew all possible squash parts.
Grew all possible toad lily parts.
Purchased all garden upgrades.
Grew all possible sunflower parts.
Grew all possible lilac parts.
Beat the tutorial.