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