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