While much of the marketing of loofahs shows the sponge in a seaside setting, surrounded by seashells and the like, loofahs are not the remains of an oceanic creature (unlike sea sponges). They’re the fibrous flesh of the mature luffa gourd — and you can grow them in your home garden.
Luffa, a.k.a. loofa or loofah, refers to two species of gourd: Luffa aegyptiaca (the angled luffa, ridged luffa, Chinese okra, or vegetable gourd) and L. acutangular a.k.a. L. cyclindrica(the smooth luffa, Egyptian luffa, dishrag gourd, or gourd loofa). Angled luffa has long ridges running the length of the fruit while smooth loofa has a rounder profile, with shallow creases running the length of the fruit. The species are used pretty much interchangeably and both are vigorous annual vines with showy yellow flowers.