Eggplant

Introduction

Eggplant (family Solanaceae; Solanum melongena) is thought to have originated in southern to southeastern Asia. Eggplant is closely related to pepper, tomato, tobacco, and potato, and shares many pests with these crops. Cultivation methods are similar to those for pepper, but eggplant is more heat-tolerant and cold-sensitive than pepper. Deep, well-drained sandy loam soils are ideal for eggplant. Southern slopes that warm early in the spring may yield better.

Types and Varieties

Eggplants come in a diverse array of shapes, colors, and sizes, and preferences vary widely among markets. The most common type is large, oblong, and deep purple with a green calyx, often marketed as Italian. Asian types are long and slender, often deep purple with purple calyxes. Specialty varieties include different colors, shapes, and sizes. Some varieties are marketed specifically for high tunnel or greenhouse production.

Soil Fertility

Apply lime according to soil test results to maintain soil pH at 6.5–6.8.

Use a liquid starter fertilizer at transplanting, especially with cool soil conditions. Use a high phosphorus starter fertilizer mixed according to label directions (typically 3 lb/50 gal of water). Apply 8 fl oz (1 cup) per transplant. If plants are to be grown on plastic mulch, the amount of nitrogen (N) fertilizer to be sidedressed can be reduced, since leaching is minimized. Nitrogen can be applied through drip/trickle or overhead irrigation. Drip fertigation is especially advantageous with plastic mulch. Too much N fertilization will lead to plants that are bushy, leafy and slow to bear fruit. See the Plastic Mulch and Row Covers and High Tunnels sections for more information.

Less N fertilizer will be needed if legume sod was plowed down or if manure was applied (see Table 1 and Table 7).

Plant Nutrition Recommendations According to Soil Test Results for Eggplant

Planting

Eggplant is normally grown from transplants. Between 2 and 4 ounces of seed are required to produce plants for one acre. Germinate seeds in flats at 70ºF–75ºF. Move to 50-cell trays after emergence. Sowing directly into 50-cell trays will shorten the time needed to produce transplants by approximately 1 week. Good transplants are 6–8 weeks old, fairly large, and slightly hardened. Transplant in the field with 18" (small plant types) to 30" (large plant types) between plants. This requires 40 or 66 plants per 100' of row, respectively. Allow 36"–42" between rows. Eggplants are much less cold-hardy than tomatoes. Plant eggplants out after overnight low temperatures are consistently above 50ºF.

Field Culture

The use of black plastic mulch will usually result in increased early growth and yield with less damage from Verticillium wilt, perhaps because the plant is more healthy and vigorous at the time of infection. Eggplant benefits from irrigation during the period of flowering and fruit set. If soil moisture is limited at this time, yields will be reduced. Large plants may benefit from being staked and trellised. Use one 4.5' stake per plant. Temperatures above 90ºF and night temperatures below 60ºF or above 70ºF can cause poor flowering and flower drop. Fruits are also vulnerable to sunburn so maintaining healthy foliage to protect the fruit is critical. 

When growing eggplant in a high tunnel or greenhouse, consider trellising to prevent plants from toppling and to improve ease of harvesting later in the season. Pruning to a 2- or 4-leader system may improve yields, although labor cost tradeoffs should be considered for your farm.

Harvest and Storage

Fruit should be harvested by clipping them off with sharp shears when the outside color is a glossy purple, the fruit is firm, and before the seed changes color. Soft fruit, loss of glossy color, and dark-colored seed are signs of over-maturity. Harvest fruit as they mature to ensure continued fruit set. Fruit can be stored up to 10 days at 50ºF–54ºF and 90%–95% relative humidity. Eggplants are susceptible to chilling injury if held in temperatures that are too cold.