The mallow plant, or Althaea officinalis, grows in marshes:
Most of the mallows have been used as food, and are mentioned by early classic writers with this connection. Mallow was an edible vegetable among the Romans; a dish of marsh mallow was one of their delicacies. Prospero Alpini stated in 1592 that a plant of the mallow kind was eaten by the Egyptians. Many of the poorer inhabitants of Syria subsisted for weeks on herbs, of which marsh mallow is one of the most common. When boiled first and fried with onions and butter, the roots are said to form a palatable dish, and in times of scarcity consequent upon the failure of the crops, this plant, which grows there in great abundance, is collected heavily as a foodstuff.
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The root extract (halawa extract) is sometimes used as flavoring in the making of a Middle Eastern snack called halva. The flowers and young leaves can be eaten, and are often added to salads or are boiled and fried. The later French version of the recipe, called pâte de guimauve (or guimauve for short), included an egg white meringue and was often flavored with rose water. Pâte de guimauve more closely resembles contemporary commercially available marshmallows, which no longer contain Althaea officinalis. Horace mentions it in reference to his own diet, which he describes as very simple: Me pascunt olivae, me cichorea levesque malvae (“As for me, olives, endives, and mallows provide sustenance”).
Educational. All these years I had no idea marshmallow had once had such roots. Heh.