Water Pepper Non-GMO Herb & Microgreens Seeds. Persicaria hydropiper (syn. Polygonum hydropiper). AKA: Asian Marshpepper, Knotweed, Smartweed. A perennial herb grown for its spicy flavoring, used in Asian dishes. As a microgreen is is a striking beauty. Avocado green with a mahogany stem and leaf reverse, it is a great addition to a microgreen lineup. Beginning with a fresh green flavor, it finishes with sharp peppery mustard. Try it in a salad with a Raspberry Balsamic vinaigrette.