Marshmallow leaves were used commonly in ancient Egypt and Rome, often in the place of vegetables. They bloom in late summer. The leaf of this Eurasian plant has a long history of documented use by the ancient Romans, Greeks and Chinese. JustIngredients Limited supplies a range of products that are internationally sourced from approved suppliers. The official website for everything Marshmello. Fresh leaves can be chopped and added to salads, they can also be used to make tea. Marshmallow Leaf Tea.