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