Ha, great question!!! How can I decide?
Vegetable: Eggplant
Herb: Basil
Flower: Grevillea
BUT!!!! I can't eat eggplant raw, and there's more special medicinal herbs, and nicer smelling flowers, so:
Vegetable: Fennel
Herb: Withuania (Indian Ginseng)
Flower: Rose
Under different criteria, I'd choose different ones! Thanks for asking - fab question, and impossible to answer!