Last revised February 5, 2010
VARIETIES (approximately 65-85 days from transplanting in the Willamette Valley).
See the Vegetable Variety Selection Resources page to find varieties that have been shown to perform well in the Pacific NW.
Eggplant. Photo credit: John McQueen, Oregon State University
Choose well-drained, moderately fertile, sandy loam soils. Use soil tests for liming and fertilization applications. Fertility requirements are similar to those of tomato and pepper.
To reduce risk from verticillium wilt and other diseases avoid using fields in which tomato, pepper, potato, strawberry or caneberries had been planted.
SEED AND SEED TREATMENT
Eggplant seed numbers approximately 104,000 per pound. Use treated seed. Plant only after soils reach 60 F, optimum germination 75-90 F. Advances in seed priming and coating can improve germination under cool soil conditions. Consult your seed dealer about the availability of primed seed.
TRANSPLANT PRODUCTION AND TRANSPLANTING
Eggplant requires a long growing season, so transplants are most commonly used. They are usually started in the greenhouse or hotbeds. Sow seeds in shallow flats of soil mix 9 to 10 weeks before transplanting to the field. Constant temperatures must be maintained as young plants are easily checked by cool temperatures or droughts. Transplants grown in the greenhouse should be kept at the following temperatures for best results:
Days: 70 to 81 F; nights: 64 to 70 F.
Use transplants grown in jiffy pots or similar containers so as to minimize shock of field transplanting.
Use starter solution made up of 3 lbs 10-34-0 in 50 gallons of water and apply l/2 pint of this solution around the roots of each transplant at time of planting.
Rows 3 to 4 feet apart, plants in the row 1.5 to 2 feet apart.
For the most current advice, see Nutrient Management for Sustainable Vegetable Cropping Systems in Western Oregon, available as a free download from the OSU Extension Catalog
A soil test is the most accurate guide to fertilizer requirements. The following recommendations are general guidelines. Adjust pH to 6.0-6.8.
Nitrogen: 75-120 (N) lb/acre
Phosphate: 100-150 (P205) lb/acre
Potash: 50-150 (K20) lb/acre
Sulfur: 20-30 (S) lb/acre
Sidedress with 30-50 lb N/acre after the first flowers are set. In wet years apply an extra sidedressing. Where mulching and trickle irrigation are practiced, additional N can be fed through the trickle irrigation system at 15 lb/acre when the first fruit begins to set and an additional 15 lb/acre four weeks later. To prevent clogging or plugging from occurring, use soluble forms of N (urea or ammonium nitrate) and chlorinate the system once a month with a 10 to 50 ppm chlorine solution. Chlorinate more frequently if the flow rate decreases.
Maintain uniform growth. Eggplant may require 14-16 inches of water in western Oregon, depending on seasonal variation and variety. Approximate summer irrigation needs for the Hermiston area have been found to be: 3.5 inches in May, 5.0 in June, 7.5 in July, and 7.0 in August.
Soil type does not affect the amount of total water needed, but does dictate frequency of water application. Lighter soils need more frequent irrigation, but less water applied per irrigation.
GROUND MULCHES AND ROW COVERS
Black plastic ground mulches may increase soil temperature, control weeds, and conserve moisture, increasing yield and earliness. Black plastic ground mulch is recommended for Western Oregon in particular. For black plastic mulch to increase soil temperature, it is critical that the soil surface be smooth and that the plastic adhere tightly to the soil surface. This can only be accomplished with a machine designed and properly adjusted for this task. Clear plastic mulch is very effective at transferring heat to the soil but does not control weeds.
A new generation of plastic mulch films allows for good weed control together with soil warming that is intermediate between black plastic and clear film. These films are called IRT (infrared transmitting) or wavelength selective. They are more expensive than black or clear films but appear to be cost-effective where soil warming is important.
Plastic, spunbonded, and non-woven materials have been developed as crop covers for use as windbreaks, for frost protection, and to enhance yield and earliness. They complement the use of plastic mulch and drip irrigation in many crops.
Non-woven or spunbonded polyester and polypropylene, and perforated polyethylene row covers may be used for 4 to 8 weeks immediately after transplanting. Covers should be removed when plants begin to flower to allow proper pollination. Row covers increase heat unit accumulation by 2 to 3 times over ambient. Two to four degrees of frost protection may also be obtained at night. Soil temperatures and root growth are also increased under row covers as are early yields, and in some cases total yields.
Although eggplants have perfect flowers, and self-pollination would not be expected to be a problem, bees are required for good pollination. Usually, wild bees are adequate, but if they are not present, bees should be provided.
HARVESTING AND HANDLING
Approximate average yields of eggplants are 190 cwt/acre with good yields about 250 cwt/acre.
Harvest eggplant fruit when they have developed full bright color for the variety, but while they are still firm to touch. At this stage, the seeds will be young, white, and tender and the flesh firm and white. As the fruit passes the prime stage for eating and becomes over-mature, the fruit surface becomes dull, the seeds harden and darken, and the flesh becomes spongy. Prompt picking increases fruit set and yields.
STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)
Eggplants should be stored between 45 and 55 F with a recommended humidity of 90-95%. Eggplant fruit are chilling sensitive at 50 F and below and deteriorate rapidly at warm temperatures, so they are not adapted to long storage. Pitting, surface bronzing, and browning of seeds and pulp are symptoms of chilling injury, and loss of sheen and wilting are symptoms of normal deterioration. Sensitivity of eggplants to chilling differs with cultivar, maturity, size of fruit, and season of harvest. Fruit harvested at optimum maturity or in midsummer are more sensitive than those harvested at an over-mature stage or in the fall, when the growing temperature is cool. Thus, eggplants harvested in midsummer can be held about a week at 55 F, whereas those harvested in fall can be held about 10 days at 48 F. Exposure to ethylene for 2 or more days hastens deterioration.
Wrapping eggplants with shrink film reduces weight loss and maintains firmness, due to the high relative humidity. However, wrapped eggplants decay rapidly if the film is not perforated. Shrink-film wrapped eggplants are susceptible to decay caused by Botrytis cinerea and Phomopsis vexans, whereas chilled eggplants are susceptible to decay by Alternaria when removed from chilling temperature.
Eggplants are commonly packaged in: 33 lb, 1-1/9 bushel containers or wirebound crates; or cartons packed 18s and 24s, weighing 20-23 lb.