Lots of fake photoshopped purple pampas images online, I do hope you saw actual photos because they won't look anything like this.
https://www.pinterest.com/pin/...
Here is a how-to for sowing but they also contains a warning:
"Pampas grass makes many invasive plant species lists because it produces and self-sows large numbers of seeds with a high germination success rate. Left unchecked, plants can crowd out native species. Methods to control your pampas grass include pulling up seedlings manually, removing the flower plumes before the plant goes to seed, and removing developing seeds before they drop."
http://homeguides.sfgate.com/g...
