I apologize if everybody knows about this already, but I found a way to free up some building space when there are bushes in the way. In this screenshot, you'll see the wheat field can't be placed because there's a bush there.
bushbug1.jpg
However, there's a simple way to get rid of that bush using a decoration. In this case, we'll be using a Flowered Stone. Simply use the move tool and move the decoration over the top of the bush.
bushbug2.jpg
Once the decoration has been successfully moved, you'll see the bush is no longer there.
bushbug3.jpg
If we move the decoration again, the bush will still be gone and we can put down our wheat field.
bushbug4.jpg