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