Two kinds of luffa gourd, or vegetable sponge, are widely grown in the United States. Many luffas are mixtures of the two varieties. Their large, bright yellow flowers last out the day. A miniature version is less widely grown.
Luffa. Also dish rag gourd. Luffa cylindrica is by far the most commonly grown in the United States. Can grow 4-inch diameter, 30-inches long.
Ridged luffa. Luffa acutangula gets its name from ten ridges in its papery outer shell. The zucchini-like fruit is about 3 inches in diameter, 12 inches in length.
Mini luffa. Also hedgehog gourd. About the size of a golf ball, these gourds are covered with spikes and have a very fine inner sponge.