According to the USDA, eggplant is a perennial plant when grown in the tropics and an annual when grown in temperate climates. Plants grow from two to four feet tall, and need support from cages or staking. Eggplant is a warm season crop and very susceptible to frost, so plant well after the danger of frost has passed for your area.
Eggplant soil and nutritional needs are similar to tomatoes. For an abundant crop, select a planting site with good soil structure, pH, drainage and fertility.
According to the State of New South Wales Agriculture, eggplants can be grown on a variety of soils, but do best on sandy loams or free-draining, loose soils. Plants might have difficulty establishing root systems in heavy clay soils. Eggplants are best suited to sandy loams because they warm quickly in the spring, making them suitable for early plantings.
Break up eggplant planting sites in the autumn after harvesting or in the spring before planting. Use a shovel or tiller to till the soil to a depth of eight to 10 inches. In heavily compacted soils, till to a depth of 18 to 24 inches to break up the hard pan and make it easier for the plant's root system to develop. Add compost to improve the structure of your soil and provide nutrients to the soil's beneficial microorganisms.
Eggplant soil requirements include a soil pH between 6.0 and 7.0, according to the University of Missouri Extension website. Test your soil's pH and amend with agricultural lime to increase pH, making the soil more alkaline, and add sulfur to increase the soil's acidity, lowering its pH. Incorporate amendments when breaking up soil before planting.
Drainage and Fertility
Eggplant soil requirements include good drainage and highly fertile soil. If drainage is a problem in your area, plant eggplants in raised beds. Test your soil to determine its fertility, and amend accordingly with compost and fertilizer. Without a test, the USDA recommends applying two to three pounds of a 10-10-10 fertilizer for every 100 feet of planting row. Incorporate half of the fertilizer when eggplants are planted, and half after the first fruit appears.
The State of New South Wales Agriculture recommends applying extra nitrogen and potassium on lighter soils that are easily leached of nutrients.
Avoid planting eggplant in soil where members of the nightshade family have been grown in the previous year. These include tomatoes, potatoes, peppers and eggplants. These plants are all susceptible to the same diseases, and the previous year's planting soil might harbor problems that could plague this year's eggplant crop.