To grow a luffa gourd, plant the seeds in a location with full sun after the danger of frost has passed, and install a trellis to support the vine as it grows. After planting, apply an organic, nitrogen-based fertilizer to the base of the plant, and water it thoroughly. When the first flowers appear, pinch them off to encourage ample gourd growth, and prune the plant's branches. In fall, harvest the gourds and prepare them for use.
When planting the seeds or seedlings, mix equal parts soil and organic compost, and plant the seeds in the mixture. After the first flowers appear, remove the first four lateral branches on the vine to improve gourd production.
When the gourds appear, prune away any that are spotted or otherwise damaged. Harvest the gourds when they feel light and have dry yellow or brown skins, before the first frost of autumn. To prepare the gourd for use, hit the gourd on a hard surface to loosen the seeds, and cut a hole in the bottom of the gourd.
Shake the loose seeds out through the hole, and peel the skin away to reveal the sponge. Rinse or wash the sponge, and soak it in diluted bleach if it appears spotty. Dry the sponge in the sun before storing or using it.