In Treasure of Nadia Red Ginseng is one of the rarest and at the same time most important plants in the game, which must be found and collected.
The first Red Ginseng can be discovered quickly. It grows in the southwest of Estero Park. Since it is located on a hill, it can not be picked at the beginning of the game. Only when you have the Grappling Hook you can reach the plant and pick it. The Grappling Hook can be combined from Heavy Cord and the Steel Hook. You can find the Heavy Cord at the doctor’s workplace. The Steel Hook can be bought at the Squallmart. To reach the plant, stand directly from the hill and select the Grappling Hook from the inventory.
After that, more Red Ginseng plants can be found in various places in Estero Park, on Estero Key, and in the gardens of some buildings.
The plant is needed for the stories of several characters. Emily, the saleswoman at the Squallmart, needs Red Ginseng to make her love potion with it. She needs the plant in large quantities. You'll also need Red Ginseng to continue with the story of Jessica, the doctor. You need to eat the plant and then visit her. She will then regulate your blood pressure in a very pleasant way. Pricia, the masseuse, also needs Red Ginseng. She wants you to plant it in her garden. Once you've done that, a very nice reward awaits you.
In the entire game Treasure of Nadia Red Ginseng is never used to craft anything. At least I don't know any recipes using it.