Loofah (luffa), the same ones used as bath scrubbing sponges, can grow in Hawaii and be eaten as a vegetable. It is a tropical, subtropical vine related to the cucumber.
It is an attractive vine that needs to be trellised or grown on a fence. It grows 3-4″ yellow male and female flowers. The male flowers becoming prevalent when the vine is laden with fruit.
The fruit will grow fast and is harvested for eating when it is young, green and under 4″ in length. It is used in soups, and stir-fried dishes. It has a mild flavor and is a cross between a cucumber and a zucchini squash.
Grow the loofah with the intention of eating them. If you miss the narrow window and the squash gets too big to eat (because it will become fibrous) you can continue to grow them until they are mature and harvest them as sponges not food.
When the mature gourd starts to turn yellow, remove it from the vine and lay it in the sun out of the rain until it starts to turn brown. The skin is easily peeled off and washed. Use a hose with a spray nozzle to blast water through the fiber to remove any remaining flesh. Place in the sun, turning daily, to dry.
If it becomes wet or the skin is peeled too soon and some flesh remained, it may mold. Processed properly, it is white turning slightly off-white when fully dry. Drying will take one to two days depending on the weather.
Dried sponges are used in place of tradition dish sponges or in the shower or bath as an excellent foliating scrub brush. They are 100% compostable.
This fruit is a win-win situation for any Hawaiian garden.