As we celebrate Easter, it is only fitting to write about Solanum melongena, the eggplant. The eggplant is an easy-to-grow garden vegetable — fruit, if you like — and very versatile in the kitchen. It was probably domesticated somewhere in Pakistan, India, Bangladesh and Burma some 4,000 years ago. From there, it slowly spread around the world, first as an ornamental garden plant and later as a food crop. Eggplant is the English name originally used to describe an early oval-shaped, white-colored variety. Throughout most of Europe, the eggplant is known as aubergine. The eggplant belongs in the nightshade family, Solanaceae, which also includes tomato, white potato, tobacco and peppers.
President Thomas Jefferson is credited with introducing the eggplant to the continental United States. It was introduced into Hawaii by Don Francisco de Paula Marin around 1800, along with many of the garden vegetables and fruits we grow today.
When growing eggplant, the best advice to newbies is to plant in well-drained soil. If the spot you selected puddles when it rains or remains soggy for days, you will have trouble growing eggplant in your garden. While eggplant can be seeded into your garden, it is best to use 5- to 7-inch-tall transplants since they grow slowly during the seedling stage, usually taking five to seven weeks from seed to transplant size. Eggplants are heavy feeders when growing vigorously. To maximize fruit production, plan accordingly. A soil test can properly determine pH and the amount of fertilizer required for your garden soil. Soil pH should be between 5.5 and 6.8. Alternatively, if you don’t have a soil test, you can add 1 to 1.5 pounds of fertilizer such as 10-30-10 or add 10 to 20 pounds of well-aged compost or manure to 100 square feet of infertile garden soil prior to planting. At fruit set, apply 1 to 1.5 pounds of 10-30-10 or 10-20-20 fertilizer per 100 square feet of garden. Place the fertilizer in a 6- to 8-inch band around each plant. One to two tablespoons of nitrogen fertilizer, such as sulphate of ammonia, can be side-dressed 8 to 12 inches from the eggplant stem every two weeks to improve fruit size.
Many insects, mites and nematodes can cause poor plant vigor and loss of fruit yield. Plant hoppers, aphids, stinkbugs and whiteflies can suck the life out of leaves, stems and fruits, as well as spread viruses and other diseases. Thrips are attracted to the flowers where they can damage the stigma and pollen grains, preventing pollination and fruit set. Feeding on the young, developing fruit can cause fruit deformity and zipper-like tracks on the skin. Some varieties of eggplant are resistant and fairly tolerant of the rootknot nematode but heavy infestation can cause plant stress, making the plant more susceptible to drought, waterlogged soils and infection by diseases.
In Hawaii, diseases on eggplant can be very common, especially when grown under rainy humid conditions on the windward side of the island. Bacterial wilt is caused by a soil-infesting bacteria that can persist for many years in the garden soil. The bacteria causes sudden wilting of the entire plant without prior indications of infection. Other diseases, such as pythium and rhizoctonia, are common organisms that can cause damping off of young seedlings. Other organisms cause leaf and fruit necrosis, wilts and stem girdling on mature plants.
While different fruit characteristics are favored in different parts of the world, in Hawaii, choices abound due to our cosmopolitan population and great growing conditions. In general, Europe and the continental United States favor the large globes with dark purple skins, such as black beauty. The long, skinny types were noted as Japanese, while the Chinese types were not as skinny as the Japanese types. Thais cherish a small green ping-pong ball-size eggplant. Some varieties have a strong, bitter taste that can be influenced by fruit age and growing conditions. Eggplant is naturally low in calories, with only 28 calories per cup of boiled fruit. It is also a good source of calcium, magnesium, potassium and phosphorous and the skin of the eggplant is high in soluble fiber.
For more information on this and other gardening topics, visit ctahr.hawaii.edu/Site/Info.aspx or any of the local cooperative extension offices around the island.
Russell Nagata is the Hawaii County administrator of the University of Hawaii at Manoa College of Tropical Agriculture and Human Resources. He can be reached at russelln@hawaii.edu.
