If you unlock the topiary PWPs there is another way to get the weeding day set. Once you unlock the PWPs if there is no weeds in your town, create a new character, (that is, if there isn't already 4 characters in your town), and talk to Leif once you get your house put down. He will give you a piece of that series, and then you can drop the piece in front of your mayor's house or wherever you want to pick it up. Then delete the character, and repeat the process. I've heard a lot of people will be doing this / already are doing this and it is working, here is another guide if my explanation didn't make sense:
http://animalcrossingus.tumblr.com/post/77329011098/weeding-day-furniture-tip