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