Wondering how to get 3 stars on the "Nice and Tidy" achievement, or how long it will take? After clearing all obstacles (trees, bushes, rocks) from your village, you will have completed the first star of the achievement, and most likely the second. If you are like me you will probably scratch your head at this point, since you need to clear 500 obstacles, but you only started with 40 in your park.
What you may not have realized, as I had not, is that obstacles respawn slowly in your park over time. In fact, per the Clash of Clans wiki, they spawn at a rate of 1 per 8 hours. This means that assuming you have the resources and builders to clear obstacles as fast as they spawn, it will take you ~ 5 months to remove 500 obstacles and finish the achievement. Also be aware that your park can't have more than 40 obstacles at a time (so check in every 2 weeks or so, or you might hit the cap). Also, building your village too spread out can prevent obstacles from spawning.