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.
Defeat 50 Snowcaps.
Obtain the Silversword
Arrive in Winter Glade.
Defeat 50 Hayrots.
Upgrade a jar to Grade 4.
Complete Goldie's Favor.
Defeat 50 Glomps.
Upgrade a tool to Grade 4.
Defeat the Rotberg once.
Take the Lift to Autumn Town
Roll 100 times.
Defeat 50 Acorns.
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.
Wake up in Spring Hamlet.