If you've ever wondered where loofahs come from, take a trip with us.   Image: Penpak Ngamsathain / Getty Images Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent every weekday. If you’ve spent most of your life under the impression that loofahs are some type of sea sponge and that these scratchy natural scrubbers are the last thing you’d want to use on your body on a daily basis, you’re not alone. But in fact, the Luffa Aegyptiaca (often known as loofah in the U.S.) is the taxonomic name of a species of gourd that grows on land, and it’s a genetic descendant of the wild cucumber. What’s more, if it’s locally grown with minimal processing, it’s plenty soft enough for not just your skin, but plenty of other applications, too. What is a luffa? In the States, you’d be excused for not being familiar with this unique plant, as luffa is far more popular in Asia and tropical regions. In fact, very few farmers grow the plant commercially for the American market—there are just two farms in the country and, according to Brooklynn Gamble, farm supervisor at The Luffa Farm in Nipomo, California, both are located in the West Coast state. But the plant isn’t endemic to countries this far north, so cultivating it requires lots of care and attention. Luffa plants growing on vines at The Luffa Farm. Image: Courtesy of The Luffa Farm Fortunately, luffa farmer Deanne Coon was willing to offer both, which is how The Luffa Farm was born in 2000 after growing the plant as part of a friend’s biology class experiment and then spending nearly two decades experimenting. Thanks to Nipomo’s location in a decidedly non-tropical climate, Coon had to account for things like cooler seasons (she grows in greenhouses), coastal winds (also greenhouses) and gophers (she grows plants in pots instead of directly in the ground).  Now semi-retired, she and a team run the small farm peppered with avocado and citrus trees and decorated with quirky custom yard art. They also offer tours during open hours so visitors can learn a little something about luffa. Guests saunter through a steamy greenhouse where long green gourds that resemble zucchini hang from trellises in impressive quantities. They learn that while some Asian cultures raise smaller varieties that are green, tender, and edible when young, it’s not popular as a culinary ingredient in the U.S. And when they inquire about why crispy brown gourds are still hanging on the vine, they learn that luffa isn’t harvested until well after you think it’s dead. “When it’s completely brown and dry we cut it off the vine,” Gamble explains. Only then, and after it is peeled, will it finally be recognizable as the fibrous exfoliating sponge many know and love. In areas of Asia, the luffa fruit is used in culinary dishes. Image: Courtesy of The Luffa Farm It’s what’s on the inside that matters Getting to that point, however, takes time and unique biological functions that aren’t visible to the naked eye. It takes six to nine months after planting luffa seeds for them to be ready to harvest, Gamble explains (longer in winter, shorter in summer). It takes three to four months just for slim green baby gourds to start sprouting from reaching vines and the male flowers, which are necessary for pollination, to bloom.  Once that happens and pollination is complete, the squash are technically edible and ripe for picking. The inner fruit tends to be slimy like okra, so it’s a bit of an acquired taste. However, there are certainly recipes from around the world that incorporate this nutritional veggie. But The Luffa Farm isn’t in the business of unpopular produce, so the fruit is left on the vine where it can grow as large and heavy as the trellised vines can handle, Gamble continues. As that happens, the interior plant fibers act as the veins that feed water and nutrients to the seeds, the care of which is the plant’s number one directive. Those veins get thicker and denser to nourish the seeds as the gourd grows. When the gourd gets too big—about the size of an oversized zucchini—the vine, which can grow 30 to 40 feet in any direction, cuts off the water supply to the whole fruit in order to redistribute resources to other plants on the vine that are still growing. “As the vine sucks the water out and recycles it, [the gourd] dries up,” Gamble describes. When that happens, instead of rotting like most other produce, the luffa turns from deep green to yellow to brown and hard. When that happens, the gourd feels light as air because all the liquid and vegetable matter has dried up, leaving only a fibrous network of cellulose inside the now-hard, shell-like skin. That’s when it’s time to harvest. The skin is cracked open and the seeds, which can be replanted, are shaken out. Harvesters soak the whole gourd in water for five minutes, which rehydrates the thin layer of vegetable residue on the underside and then “the skin so it slides right off,” Gamble says. What’s left over is an airy, light, sponge-like spidery network of plant fibers that make an excellent natural multi-purpose sponge that’s pliable when dry and even softer when wet. That’s what makes it such an attractive option among skincare enthusiasts. Not all luffa are created equal If that doesn’t sound at all like the rigid, compressed luffa you see for sale at your local health food store, you’re not wrong. Most luffa are imported, and since they’re a plant, they must be treated beforehand to ensure they won’t transport bugs, disease, or other agricultural blights, Gamble explains.  “Those heat treatments in particular are what damage the fibers,” she states. It shrinks the otherwise light and loose cellulose structures and makes the luffa hard, compact, and less pliable. Compromising the structure also makes them more prone to bacterial growth, because they don’t dry out as easily or completely between uses. Luffas grown and sold at The Luffa Farm. Image: Courtesy of The Luffa Farm Luffa grown in the U.S., like the ones from The Luffa Farm, don’t have to be treated with anything since they’re not imported from overseas. They just get a quick rinse before they’re sold. As a result, they’re softer, more pleasant on skin, more versatile, and longer lasting. One might last up to a year of regular use. Plus, because they’re highly porous, “they don’t create the same breeding ground for bacteria,” Gamble offers. A plant with unlimited uses But exfoliating isn’t all these plants are good for. On the contrary, Gamble says there are many uses for luffa. Softer varieties can be used as a facial sponge in place of a washcloth. They can even be tossed in the washer for a deep clean, though you should avoid putting them in the dryer. They make excellent dish sponges and pot scrubbers. Gamble uses one on her stainless steel stove.  A wet luffa makes quick work of washing your car, too, especially when it comes to scrubbing bugs off your grill, Gamble recommends. The fibers won’t even scratch the finish. They’ve even been used as insulation in mud brick houses and as industrial filters and may have inspired a sunlight-powered porous hydrogel that could potentially purify water. The best part: untreated luffa sponges are compostable, making them an eco-friendly alternative to synthetic sponges. “They are so unique as a plant,” Gamble says, a truly multifunctional and sustainable natural product whose uses go far beyond bath time exfoliation. And yes, it’s one that grows on land, not underwater.