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.
Upgrade a jar to Grade 4.
Defeat 50 Glomps.
Upgrade a tool to Grade 4.
Defeat 50 Shelled Oozes.
Defeat 50 Snowcaps.
Obtain the Flute.
Vanquish the Grove's Clutch.
Obtain the Silversword
Roll 100 times.
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.
Wake up in Spring Hamlet.