Not all natural sponges are found in the sea. Luffa cylindrica is an annual gourd that can supply you with your own sponge source, all on a fast-growing summer vine. They’re grown like other gourds, but they do have some special requirements.

The seeds should be scratched or roughened with a file or emery board, and then soaked in water for 24 hours before planting. They also do best if grown on a very strong support, such as a trellis or arbor.

Luffahs take a long time to grow and need to be harvested late in the season. The outer shell should be dry, the gourd should already lightweight, and the seeds inside should rattle. Cut off the stem end of the gourd and shake out the seeds. Then soak the gourd in warm water and peel off the coating.

Soak the inner sponge in a 10 percent bleach or hydrogen peroxide solution to turn it cream-colored. Rinse thoroughly in cool water, cut to shape, and dry before using.