Here is the full list of all 18 Strange Horticulture achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Take control of the Servant
Bring about the Redemption
Identify all the plants
Complete the game
Complete a full playthrough without using the hint button
Perform the ritual
Save the Sisterhood
Create an Elixir
Find a Bryer's Disc location
Open the secret drawer
Activate the viewing device
Murder Burbidge
Visit 20 map locations
Pet Hellebore 13 times
Solve your first clue card
Identify 10 plants
Recover from Rising Dread
Handle your first customer