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