Vases, Flowers and birds respawn after you change the area. And since the spots with the most vases are between two quarters, you can just leave and immediately come back. They can't respawn while you're in the area but that doesen't bother us too much the way we do it.

If possible Upgrade your speed as far as you can and buy a bunch of sandwiches.
Then just follow and repeat the path shown in the video below.
As a nice side effect you'll get a bunch of money which can be usefull if you haven't completed the game yet.