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