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.
Defeat 50 Hayrots.
Complete Goldie's Favor.
Defeat 50 Snowcaps.
Defeat 50 Shelled Oozes.
Defeat 50 Glomps.
Vanquish the Grove's Clutch.
Defeat 50 Acorns.
Obtain the Silversword
Arrive in Winter Glade.
Upgrade a tool to Grade 4.
Upgrade a jar to Grade 4.
Obtain the Flute.
Defeat the Rotberg once.
Take the Lift to Autumn Town
Defeat the Octopihi once.
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.