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