Here is the full list of all 23 Gnomes Garden 3: The thief of castles achievements.
For defeating the evil warlock
For growing your seventh tree
For growing your sixth tree
For growing your fifth tree
For restoring the signal fires
For growing your fourth tree
For growing your third tree
For stopping time
For growing your second tree
For completing 15 levels with 3 stars
For getting rid of a Gremlin
For restoring Stonehenge
For growing a lily pad
For activating an altar
For speeding up construction
For growing your first tree
For speeding up workers
For completing 5 levels with 3 stars
For restoring a plant
For constructing a building
For clearing one roadblock
For collecting all trophies
For completing all levels with 3 stars