Answer: Gourds

If you’ve ever used a loofah in the shower and thought it looked rather distinctly like a plant, you were spot on. The thick and fibrous sponge-like product that people have been using to scrub and exfoliate their bodies for centuries is most certainly plant derived.

From the genus Luffa, but commonly spelled as loofah in terms of product marketing and sales, the common shower accessory is derived from the dried out bodies of two particular Luffa species, L. aegyptiaca and L. acutangula. The mature fruit, similar in shape and coloration to the cucumbers also found in its family tree, is harvested, dried, and treated so that the skin and pulp of the gourd is stripped away, leaving just the network of xylem fibers. Xylem is one of two types of transport tissue inside vascular plants, alongside phloem. The xylem is what gives loofah sponges their stiff and mildly abrasive bulk, making them perfect for exfoliation.

Exfoliation isn’t the only thing loofah sponges are good for—the product has a long history of use in applications outside the shower stall. In the early 20th century (pre World War II), for example, over half of the loofahs (luffa gourds) imported into the United States were used for filtration, primarily by the U.S. Navy, in everything from steam to diesel engines. They also found use as water filters, industrial scourers, and surgical tools. During the mid-20th century, they proved useful as sound proofing material for tanks, helmets, and certain kinds of buildings.

Today, however, the loofah has returned to its roots as a spa-like accessory and is scarcely used in industrial applications now.