How do you get a red turnip in animal crossing wild world

Nearly every Sunday an animal will visit your town with a bag full of turnips. ask her about them and she will tell you everything you need to know about them. WHen she's finished talking, she will ask you if you would like to buy them. Red turnips cost 1,000 for a bag of seeds but you can only plant 1. If you need to know whether she is in your town or not, go talk ot the guys in town hall and say "whats new?"