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.
Fruited a flower without growing any extra leaves.
Purchased all plants and all upgrades.
Purchased all garden upgrades.
Purchased all four plants.
Grew all possible squash parts.
Grew all possible lilac parts.
Grew all possible toad lily parts.
Grew all possible sunflower parts.
Beat the tutorial.