Here is the full list of all 21 Garden Story achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Vanquish the Grove's Clutch.
Defeat 50 Snowcaps.
Defeat 50 Hayrots.
Obtain the Silversword
Arrive in Winter Glade.
Upgrade a jar to Grade 4.
Defeat the Rotberg once.
Defeat 50 Glomps.
Take the Lift to Autumn Town
Complete Goldie's Favor.
Defeat 50 Shelled Oozes.
Upgrade a tool to Grade 4.
Defeat 50 Acorns.
Defeat the Octopihi once.
Obtain the Flute.
Reach the Summer Bar
Roll 100 times.
Defeat the Bookworm once.
Defeat 150 Enemies.
Reduce the Rot Dummy to rubble.
Wake up in Spring Hamlet.