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