To farm Pecok Flower you must go to West of Central Plains in Wuthering Waves. This Pecok Flower farming guide will show you the farming routes of Pecok Flower and the node locations.

Below are screenshots of some of the Pecok Flower node locations.

Then port to Southeast from your farming location.

There is a vendor located at Jinzhou Main City

You can buy up to 15 Pecok Flower at this vendor

Credit to WILDMAT7 for latest farming routes.