This delicious nightshade is a close relative of the tomato and potato, but has its own unique characteristics.
Planting: Give eggplants a head start on the growing season by starting them indoors, 6 to 9 weeks before the average last frost. Soak seeds overnight to encourage germination; sow them ¼ inch deep in a loose, fine medium, such as vermiculite. Use bottom heat to maintain a soil temperature of 80° to 90°F for the 8 to 10 days required for sprouting. Transplant seedlings to individual pots once they reach 3 inches. When outside nighttime air temperatures are above 50°F, gradually expose them to the outdoors to harden them off. Keep transplanting your seedlings into larger pots as you wait for both outdoor air and soil to warm up to at least 70°F.
Try growing eggplants in raised beds, which heat up quickly in spring. Plants given plenty of room are healthier and more productive, so space them 2½ to 3 feet apart in all directions. Water well, pour 1 to 2 cups of compost tea around each plant, and firm the soil gently. Learn how to make compost tea.
Eggplants are also good for container growing, with one plant per 5-gallon pot.
Problems: Flea beetles, which chew many tiny holes in leaves, are eggplant's worst pest. To avoid this problem, keep plants indoors until early summer, or cover outdoor plants with floating row cover or dust the foliage with kaolin clay (reapply it after rain). If plants become infested, spraying Beauveria bassiana or spinosad may knock back the population of flea beetles and save your plants.
Hand pick and destroy yellow-and-black-striped Colorado potato beetles and the yellow masses of eggs they lay on leaf undersides. Hand picking is also effective for tomato hornworms, 4-inch green caterpillars with white stripes. Don't destroy those covered with tiny white cocoons; these contain the parasitic offspring of the beneficial braconid wasp. Tiny spider mites cause yellow-stippled leaves; control these pests by knocking them off the plant with a spray of water.
The most common eggplant disease is Verticillium wilt. Avoid it by planting resistant cultivars and by rotating crops.
Harvesting: Pick eggplant when the skin takes on a high gloss. To test, press the skin. If the indentation doesn't spring back, that fruit is ready for harvest. To harvest, cut the stem with a knife or pruning shears. Eggplants will keep for 2 weeks if refrigerated. If you cut open an eggplant fruit and find that the seeds inside have turned brown, the fruit is past prime quality and the flavor may be bitter. The best way to avoid this is by picking fruits on the young side, when they are 1/3 to 2/3 of their fully mature size.