(Vegetable Sponge, Dishcloth Gourd) (Luffa cylindrica) 65 days for edible fruits, 150 days for sponges. The young gourds are edible and make a great zucchini substitute. Best eaten at 1 in. diameter or less. Mature, dark green 14-24 in. fruits may be retted (soaked in water to soften while the soft tissue breaks down). Once retting is complete, they are cleaned and ready to use as sponges or filters. Vines have pretty, bright yellow flowers.