A Healing Herb is a sidequest in Star Ocean: The Divine Force you can pick up at the Seaport Of Rythal.
Head to a house on the right side of Seaport Of Cotto and and inside you'll find a NPC named Sickly Woman.
She wants you to acquire some herbs called Dillwhip to help cure her sickness.
You can find Dillwhip at Cottorinth Mountain Pass as glowing green items. You'll need to collect 6 of them.
Once completed, head back to Sickly Woman to claim your reward.
Reward: