Did you know that the luffa that you know as a sponge IS actually a gourd? Luffa is a genus of tropical and subtropical vines in the cucumber family. In everyday non-technical usage, the luffa, also spelled loofah, usually means the fruit of the two species. Usually grown for its one- to two-foot-long gourds. Both varieties are edible, however, and both will produce sponges on fast-growing annual vines whose coiled tendrils grab out eagerly for support. The plant's tendency to climb makes it an ideal choice for folks who want to grow a shady arbor or a privacy screen along a fence. Many of the flowers fall off without ever forming gourds, because the plant is monoecious ... that is, it has both male and female blossoms on the same vine. The male blooms drop, while the females remain attached to the developing fruit. Once pollinated, the vegetables fairly rush toward maturity, growing at the rate of an inch and a half a day. If you want to eat your luffa fruit, pick it young, before its fibers toughen up. In general, luffas are harvested for culinary purposes when they're about four inches long, but the smaller the gourd is, the tenderer its flesh will be.