Lufa sponges (Luffa aegyptiaca, synonym L. cylindrica) are commonly found in health-food stores, where they are sold as exfoliators and displayed alongside soaps, shampoos, and other bathing supplies. It’s common to mistake a luffa for a sea sponge, but it’s actually a gourd that you can grow and process in your own backyard.
What is a Luffa?
Luffa is an annual subtropical vine in the Cucurbitaceae family with large leaves, buttery yellow flowers, and fruit that resembles giant cucumbers.
The young, edible fruits, which taste like a cross between a cucumber and a zucchini, can be harvested when they are just a few inches long and used in stir-fries, chutneys, and soups.
When the fruit is allowed to mature and dry on the vine, the edible flesh transforms into a fibrous woven skeleton with brown skin and rattling seeds. We use this textured skeleton as a sponge.
Use luffa sponges to scrub dishes, scour surfaces, clean your car, add an exfoliating layer to homemade soaps, make a DIY back scratcher, or even to apply textured patterns to a freshly painted wall.
Gardeners can also soak luffa fibers in water to hold a rooting plant or mix them into potting soil to replace peat moss.
There are numerous creative and fun ways to use Luffa, and because it is such a productive plant, you will have plenty of sponges to give as gifts!
How to grow Luffa
Luffa gourds require a long growing season because they are left to mature and dry on the vine (nearly 200 frost-free days in a row).
North of Zone 8 gardeners can accomplish this by starting luffa seeds indoors 6 to 8 weeks before their average last spring frost.
You can boost luffa seed germination by scratching the seeds on sandpaper to weaken the seed coating (a process known as “scarification”) or by soaking them in water for 48 hours before planting.
Plant two or three seeds in each container, 12 to 34 inches deep. Luffa seeds sprout slowly, so be patient while maintaining a moist, well-drained soil medium and plenty of light.
Thin the seeds to one seedling per container once they sprout. To keep the seedlings from becoming root-bound, transplant them to larger containers.
Lufa seedlings resemble cucumber seedlings once they develop their first set of true leaves. If you don’t label your seedlings properly, you might confuse them with other cucurbits.
Luffas are not frost-tolerant, so wait until the frost has passed before transplanting seedlings to your garden. Spend about a week gradually hardening off your seedlings before transplanting.
Carry them outside and place them in a shady location for a few hours each day, gradually increasing the number of hours each day. Place seedlings in a shady spot, or the sun will scald their delicate leaves.
Choose a sheltered location where a light breeze can tease and strengthen the stems while protecting them from strong winds that could snap their fragile bases.
When all danger of frost has passed, move your hardened-off luffa seedlings to a well-drained, full-sun location.
Plant your seedlings (or seeds, if you live in a warmer climate) 3 to 4 feet apart, and give them an inch or two of water per week.
I mulch my luffa plants with a layer of cardboard topped with 2 to 3 inches of straw, which helps the plants retain moisture and makes weeding between the vines easier.
Luffa vines can grow to be more than 20 feet long, so plant seedlings along a trellis or a sturdy fence to keep them in check.
I grew luffas next to a 3-foot-tall hog panel, which was near a 5-foot-tall fence, on the other side of which 7-foot-tall marshmallow plants were growing in my Zone 6a garden.
By the end of the summer, the luffas had climbed over both fences and spread their tendrils all over the giant marshmallow, dropping their fruit among the tall stems of the marshmallow.
Trellises are especially important when growing Luffa because they ensure straight fruits that are easier to peel and produce more appealing and uniform sponges.
Because luffa vines and flowers are so beautiful (but require so much space), gardeners should consider growing them on a trellis along one side of a house or near a porch to provide shade.
Some sources recommend removing the first flowers of the Luffa to produce stronger sponges and encourage more vigorous production; I’ve never done this, and my yield has always been satisfactory.
Experiment year after year to see what works best for you.
How to harvest Luffa
Gardeners in the desert southwest and subtropical growing climates should have enough frost-free days to allow luffas to mature on the vine.
The skins will turn brown or brownish yellow, the fruits will lose almost all of their water weight, and shaking the gourds will reveal the seeds rattling around inside. It’s time to pick and process your luffas when they reach this stage.
Gardeners in colder climates should harvest all luffa gourds immediately after the first hard frost, regardless of maturity level. If you leave the fruits on the vine after a frost, they will rot rather than mature.
Many of them will still be green and wet—this is fine. Simply process them differently and allow them to dry for a longer period of time than luffas dried on the vine.
My luffa sponges are all from green and immature fruits, and I have no complaints about their quality.
How to process Luffa
Pick mature luffas with brown skin from the vine and place them in a shady, out-of-the-way location for a few days to completely dry.
Break off the end of the Luffa where it was attached to the vine; this should come off easily, and a slew of seeds will flow out.
Southern gardeners are fortunate in that you will not have to work as hard as Northern gardeners to remove the numerous luffa seeds, which can be saved and planted the following year.
Begin by slamming your gourd against a tabletop or hurling it on the ground to loosen and crack the tough outer skin. You’ll be able to easily crack open the gourd and peel off the skin once the skin has become loose.
Luffas have a lot of vertical seams, so if you find one and run your thumb along it, you’ll be able to easily separate the skin from the sponge.
If the skin does not easily come off, soak the mature gourd in water for a few hours. Peeling the Luffa should be easier after that.
If you want to use them in soap molds, cut them into small discs. Allow the cut sponges to dry for a week or two in a well-ventilated, sunny location, rotating them every few days.
Before storing your luffas, make sure they are completely dry; otherwise, mold and mildew may grow.
In my experience, it’s best to process immature luffas right away after harvesting, or the green squash will develop mildew and rot.
Begin by slamming your luffa gourds on a table or throwing them on the ground to loosen and separate the skin from the fruit. Push your thumb into the gourd until the skin cracks, and you can begin peeling it away.
Luffas have fibrous strings that run vertically up and down the fruit’s seams; pull these cords to “unzip” the sponge from its skin.
If you start peeling an immature luffa and the inside looks more like a mushy banana than a fibrous sponge, throw it away; it isn’t mature enough to use.
Immature luffas are more difficult to remove the seeds from, so plan on spending about five minutes per gourd poking out seeds with a chopstick and rinsing the gourd under water.
While rinsing, you’ll notice the Luffa emitting a slimy, soap-like substance. This is sap, and you should rinse it off as thoroughly as possible.
Cut the gourd into sponge-sized pieces (or small discs if you intend to use them in soap molds) and place them in a well-ventilated and sunny location to dry thoroughly for 3 to 4 weeks.
Rotate them frequently and store them only when completely dry.
You can easily provide your household with a year’s supply of organic, nontoxic, compostable sponges by growing 5 to 10 luffa plants. When your friends and family hear about your latest venture, they’ll be sure to ask for sponges as well.
Useful resources to check out: