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.
Defeat 50 Glomps.
Upgrade a jar to Grade 4.
Defeat 50 Shelled Oozes.
Defeat 50 Snowcaps.
Upgrade a tool to Grade 4.
Complete Goldie's Favor.
Obtain the Flute.
Vanquish the Grove's Clutch.
Obtain the Silversword
Defeat 50 Acorns.
Arrive in Winter Glade.
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.