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.
Upgrade a jar to Grade 4.
Defeat 50 Snowcaps.
Obtain the Silversword
Arrive in Winter Glade.
Complete Goldie's Favor.
Upgrade a tool to Grade 4.
Defeat 50 Hayrots.
Roll 100 times.
Take the Lift to Autumn Town
Defeat the Octopihi once.
Defeat the Rotberg once.
Defeat 50 Acorns.
Defeat 50 Shelled Oozes.
Defeat 50 Glomps.
Obtain the Flute.
Reach the Summer Bar
Defeat the Bookworm once.
Defeat 150 Enemies.
Reduce the Rot Dummy to rubble.
Wake up in Spring Hamlet.