Luffa sponges are the fibrous interiors of luffa gourds, which grow on several warm-season annual vines, including smooth luffa (Luffa cylindrica) and angled luffa (Luffa acutangula). Smooth luffa gourds, or fruits, grow 12 to 24 inches long and 4 to 5 inches thick, and angled luffa gourds are about 12 inches long and 2 to 3 inches wide. Sharp ridges line angled luffa gourds.
Sowing Luffa Seeds
Luffa gourds are ready for harvest about 150 to 180 days after the plant seeds were sown. If your area experiences frosts, then sow luffa seeds indoors three to four weeks before the location's final average frost date.
Sow three seeds in general-purpose potting soil in a 4-inch-diameter container with bottom drainage holes, and water the container's soil regularly so that it remains moist.
If you are in a frost-free zone, sow luffa seeds outdoors when the soil reaches at least 60 degrees Fahrenheit in early spring. Sow three to six seeds in a hill, and space the hills 3 to 4 feet apart. Water the soil after sowing the seeds and whenever the soil surface is dry.
Pre-soaking luffa seeds in warm water for 48 hours before sowing helps them sprout quickly.
Planting Luffa Vines
- Plant indoor luffa seedlings outside after the final average frost date.
- Form hills out of the soil 1 1/2 times as deep and twice as wide as the plant pots.
- Dig holes the size of the plant pots in the hills, and remove the seedlings from their containers before planting them in the holes.
- Plant the seedlings at their original soil depth.
- Water the seedlings' soil after planting and when the soil surface is dry so that the ground stays moist to a depth of 9 inches.
If a late frost is forecast, cover luffa seedlings with several sheets of newspaper or cardboard overnight.
Growing the Vines
Luffa vines grow best in sunny spots with freely draining soil. The vines grow well in low-fertility soil and don't need fertilizer. Water the soil of strongly growing vines when the soil is dry to a depth of 2 inches. Luffa vines grow 15 feet or longer.
Grow luffa vines on a trellis or another supporting structure to prevent their gourds from touching soil, which causes rotting.
Creating the Sponges
Ripe luffa gourds make the best sponges. When the gourds ripen, their stems turn yellow and their skins become dry. Full-size, unripe luffa gourds also can be made into sponges, but those sponges are finer textured and don't last as long as sponges made from ripe gourds.
- Place ripe gourds in a sunny, dry spot, and leave them there for two weeks.
- Wait for the skins to become brown and hard. Then open the large ends of the gourds, and shake out the seeds.
- Place the gourds in water, and leave them in it overnight.
- Peel off the skins.
- Place the gourds in sunlight to dry.