Luffa sponges are easy to grow from seed, but the plants are cold sensitive and must be started indoors to allow enough time for ripening during the growing season. Harvest, clean and dry the mature fruit of the luffa vine to create natural vegetable sponges. The plants make an attractive and useful addition to the home garden. The vines can reach up to 30 feet in length and produce large, tropical-looking leaves and attractive yellow flowers.
Start luffa seeds indoors about 3 weeks before the last frost date in your area. Soak them in water overnight to help speed germination, as luffa seeds are characteristically slow to sprout. Plant seeds about ½ inch deep in peat pots and water thoroughly to initiate growth.
Place the peat pots in a warm, dry place that receives some indirect light. Water the seeds at least twice per week, or often enough to keep the growing medium slightly moist at all times. Keep the temperature at 70 to 80 degrees F for the best results. Germination should occur within 2 weeks.
Continue caring for the luffa seedlings by watering twice per week and providing indirect light until all danger of frost has passed. Choose an outdoor planting location with full sun and average soil. Provide a trellis for support or plant your luffa seedlings against a fence that is at least 5 feet tall.
Prepare the planting site by creating small hills in the soil about 6 feet apart. If creating multiple rows, space each row 3 to 4 feet apart. Plant one luffa seedling in each hill about 6 inches from your chosen support structure. Water immediately to compact the soil.
Water your luffa plants about once per week, allowing the soil to dry out slightly between applications. Never allow the soil to dry out completely or become soggy. Increase watering to twice per week when temperatures rise above 90 degrees F or during times of drought.
Mulch luffa gourds in midsummer by applying a 2- to 3-inch layer of grass clippings to the soil surrounding each plant. This will prevent the fruit from decaying due to contact with the ground and also suppress the growth of weeds. Replenish as necessary throughout the growing season.
Harvest luffa for making sponges when the fruit is about 12 inches in length, yellow in color and dry to the touch. Green luffa gourds will produce soft sponges that do not last long. For the best results, make sure the fruit is completely ripened before harvesting.
Make luffa sponges by soaking the ripened gourds in warm water for 2 to 3 days, and then peel away the skin, which should come off easily after soaking. Wash the luffa well to remove all seeds and pulp, and then place in the sun to dry for about 1 week before using.