What you might not know about luffa is that when they are still young and tender, luffa gourds are actually edible vegetables in the cucumber family that can be eaten raw or cooked. However, the fruit grows so fast, about an inch-and-a-half per day, that it’s difficult to keep up with harvesting them on time so it’s best to grow luffa for sponges and let them grow to about two feet long. Large yellow blooms precede the gourds, attracting bees and butterflies. Because luffa vines can reach a length of up to 30 feet, with palm-shape leaves up to ten inches wide, growing them on a trellis is best, and not merely for space reasons. Luffa that is grown on the ground tends to be curved, and keeping the vines and fruit off the ground and dry reduces the risk of disease and rotting in humid or wet weather. Luffa vines grow vigorously and fast and need a very sturdy trellis to keep the fruit off the ground and ensure good air circulation. Soil contact may lead to fruit rot, discoloration, and misshaped curved gourds. A trellis like those used for cucumbers and pole beans works well, as long as the trellis is strong enough to support the weight of the mature luffa gourds. Or, use four-by-four-inch posts, set ten feet apart, with heavy gauge horizontal wires at even intervals all the way to the top. To train the vines, add string in a V-pattern so the tendrils of the vines have something to grab onto.
Light
Luffa needs at least six or more hours of full sun—the more the better.
Soil
Luffa can grow in any soil type (it prefers a pH range of 6.0 to 6.5), however it requires good drainage. Make sure you can offer a well-draining soil that will prevent your luffa plant from over-saturating.
Water
Keep the soil moist but not wet until the seedlings are established. After that, in the absence of sufficient rain, water the base of the plants about 1 inch per week. Do not water the vines, which can spread disease,
Temperature and Humidity
Luffa needs warm to hot weather. In cool weather, its growth will slow down.
Fertilizer
Add organic matter to the soil before planting, and add nitrogen-rich fertilizer two to three times during the growing season. For the amount to use, follow the product label instructions.
Types of Luffa
Luffa aegyptiaca is the variety most widely available from seed companies. There are two other luffa varieties:
Angled luffa (Luffa acutangula), whose immature fruits are popular in Asian cuisine Ball luffa (Luffa operculata), used as a fibrous scrubbing sponge just like Luffa aegyptiaca
Harvesting
Luffa is ready to be harvested in the fall when they are tan in color and lightweight, and their skin has fully dried to a hard shell. When you shake a luffa, you should hear the seeds rattle, which is a sign that the inside fibers have dried and hardened as well. Cut the fruit from the vine with one to two inches of the stem attached. To make sponges, immerse the luffa in warm water for about 20 minutes, or until the skin can be easily removed. Remove the seeds by shaking them loose, and remove any pulp. Once you have gutted the luffa, soak in a 10 percent bleach solution for one hour to clean it. Rinse it well under fresh water and shake it to remove excess water, then dry in a warm well-ventilated place before storing.
How to Grow Luffa from Seed
Because of its long growing season and warm temperature requirements, luffa is best seeded directly in your garden. Starting the seeds indoors would require four to six weeks in a greenhouse-like setting at about 65 to 70 degrees F with full sunlight, which is not practical for most home gardeners. In late spring when the soil has reached at least 70 degrees F, sow seeds in well-drained, tilled soil, three to four seeds per plant, and leave about six feet between the plants. Do not plant luffa in a location where you grew other members of the cucumber family (Cucurbitaceae) the year before. Cover the seeds with a half inch to three-quarter inch of fine soil, firm it lightly and keep evenly moist. The seedlings ideally emerge in seven to 14 days but germination can be slower depending on the seed quality and soil temperature. Thin to one seedling per plant when they are one to two inches high. If you don’t have a trellis in place from the start, make sure you keep a safe distance from the tender root system when you drive the posts into the ground.
Common Pests & Diseases
Downy mildew, powdery mildew, alternaria leaf blight, and angular leaf spot have been observed on luffa but thankfully luffa is not frequently affected. The same holds true for pests, which can include cucumber beetles and spider mites. Practicing crop rotation, and avoiding overhead irrigation helps reduce the spread of disease.
