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