If you're looking for an unusual garden plant, add a few loofah sponge vines (Luffa spp.) to your vegetable plot. Also known as vegetable sponge, it's a cucumber relative that produces a gourd that's edible when young. When fully mature, the gourd has an inner fibrous network that's useful as a bath sponge. The plant needs a long growing season but does well with lots of sun and just a bit of extra care.
Loofah vines come in two types, the ridged loofah (Luffa acutangula), which has extra-tasty young fruits and also makes sponges when mature, and the common loofah (Luffa cyindrica), which produces large, 1- to 2-foot long gourds usually used for sponges. Both types of vines are frost-sensitive and grown as annuals in all parts of the United States.
If spring tends to be cool where you live, start seeds indoors about three weeks before your expected last frost. In warmer areas, direct-seeding into the garden works well; in both cases, scrape the outer coat of each seed with a nail file, then soak in warm water for 24 hours to speed germination, which can take up to two weeks. Once danger of frost has passed and the soil has warmed a bit, plant seeds or seedlings in the garden.
Supporting Strong Growth
Grow loofah plants in a spot that gets full sun, setting one to three seedlings or seeds in small hills that are about 6 feet apart. The vines can become up to 15 feet long and grow best with support. Set a 5- or 6-foot tall trellis or fence into the ground beside each hill and tie vines to it with soft ties.
Remove the first four side branches from each vine to spur production of stronger vines and better fruits. When fruits appear, ensure they hang freely without any constriction, which can cause them to be deformed.
Loofah vines need constant moisture while growing, so water whenever the soil's surface feels dry to the touch. Add 2 or 3 inches of organic mulch under each vine to helps conserve soil moisture, but keep it back a few inches from the plant's base to discourage fungal problems.
The plants also do best when fertilizer is added to soil at planting and again during the growing season. Add 2 tablespoons of a granular, 6-10-10 formula to each hill at planting, then mix 1 tablespoon of a high-nitrogen formula such as ammonium nitrate, which is 33-0-0, into a furrow around each hill one week after flowering begins and again three weeks later.
Avoiding Pests and Diseases
These plants are susceptible to several fungal problems that include gummy stem blight, which causes brown-to-yellow spots on leaves and stems, and black rot, which causes black spots and soft, wet areas on fruits. These are best prevented by spacing plants properly, removing plant debris regularly and watering at the base of the plants with a soaker hose or drip irrigation to keep foliage dry. If you encounter either of these problems, don't re-plant in the same spot for three or four years. The plants might also attract striped cucumber beetles, which suck plant juices and weaken the vines, so hand-pick these if they appear.
Harvesting Fruits and Preparing Sponges
The loofah gourds usually ripen in the fall, when they're ready to become sponges. Their skins dry out and the stems turn yellow. Each loofah also seems to lose weight and seeds rattle inside as it dries. Remove each fruit by snapping its stem off the vine, and don't leave any on the vines after the first frost, or they'll spoil. When ready to process sponges, break off the end of the gourd opposite the stem and shake out the seeds, then put the gourd in water to soften it, changing the water several times.
These vines cross-pollinate with cucumbers and squash, so don't save seeds for planting next year if these crops are grown nearby.
Remove and discard the skin and soft pulp from the softened loofah, and soak the remaining fibrous part -- the sponge -- in a bucket containing 3 parts bleach and 7 parts water for about 15 minutes, or until it whitens. Rinse the sponges in clean water and dry them in the sun.