There are more than 30 varieties of eggplant to choose from. In Hawaii the more common cultivars are ‘Waimanalo Long,’ ‘Florida Market,’ ‘Burpee hybrid’ and ‘Black Beauty.’ The former is the long oriental type and the latter three are round types. The two most common used for pickling are ‘Black Egg’ or ‘Money Maker.’ Most of the varieties are available either as transplants or seed packages at garden centers around the state.
As the temperatures warm up its time to start seeds of warm weather crops. One garden vegetable that loves the heat is eggplant. In the same family as the tomato (Solanaceae), it is known by scientists as Solanum melongena. The round-fruited types are known as S. melongena var. esculentum and the long-fruited types, as S. melongena var. serpentinum. Dwarf types are known as S. melongena var. depressum. Besides the common name of “eggplant” it has also been called garden egg, bringal, aubergine and melongene (note the similarity to the species name).
Description and Culture
Eggplants are short-lived perennial herbs or shrubs with a branching habit. They can attain heights of nearly 8 feet, but this depends on the type grown. They have a deep tap root and can reach down to find moisture and nutrients in loose soil. They prefer well-drained, sandy soils that have good moisture retaining properties.
The roots do not like to be overly wet and will rot if too much moisture remains in the soil, so avoid poorly-drained soils. Eggplants prefer a pH of 5.5 to 7.5 and temperatures from 75° to 85° F. Temperatures below 63° and above 95° can be detrimental. The most satisfactory growth is found at lowland coastal areas with little variation in temperature but it can be grown successfully up to 3,000 feet in the summer months.
High soil temperatures can injure the root system so mulching is advised. Too much rainfall will hinder both vegetative growth and fruit production, so Hawaii’s dry season coinciding with the hotter months is perfect for eggplant production. Irrigation is needed during fruiting to make sure fruit develop properly. Try not to get the flowers wet but do keep the roots moist.
Eggplants can be grown in containers. It is best to choose varieties that are dwarf or at least bear smaller fruit at a younger age. Read the seed packets or catalog descriptions for that sort of information. Use a 5-gallon container filled with a regular potting mix.
If you have soil problems that prevent you from growing eggplants in the garden, this is a good alternative to garden-grown plants. Keep the soil moist but not wet and follow the same recommendations as below. Because eggplants need high light levels (full sun) and high temperatures to produce well, they should only be grown in containers with southern or western exposures that are not obstructed by tall buildings or mountains.
Propagation and Planting
To propagate eggplant, it is best to start with fresh seed. Seeds of eggplant can be stored in the refrigerator for up to four years and still maintain a germination percentage of 60 percent. Longer storage times will decrease germination percentages. To speed up germination, soak the seeds in room temperature water for 24 hours.
Sow seeds in pots for later transplanting into the garden, or directly in the garden. Keep in mind that soil temperature below 60° and above 95° F will decrease germination. Once the plants reach several inches tall, transplant to the garden in rows or raised beds.
If in rows, plants should be about 2 to 2½ feet apart with rows about 2½ to 4 feet apart. If they are planted in raised beds on a square grid, plants should be from 18 to 24 inches apart. It is wise to remove the terminal bud to encourage branching. This makes for a bushier plant and also creates more branches for flower and fruit production.
If you want to save seeds (for any variety that is not a hybrid) keep in mind that the flowers are both self-pollinated and cross-pollinated. There is about a 20 percent chance of cross-pollination, so to get seed that will reproduce true to form, there should not be any other varieties within 1,500 feet.
Eggplants can also be propagated by stem layering. This is similar to air layering. Make a shallow cut on the underside of a low-lying stem. The cut should reach into the xylem (inner stem) but not all the way through the branch. A rooting hormone can be applied at this point, but is not necessary. Bury the cut section of the stem with a mound of moist soil.
Keep the soil moist but not wet. A mulch can be applied over the mound to retain moisture and keep the soil from getting too hot. After about six to eight weeks, gently brush away some of the soil to see if roots have formed. If they have, you can then cut the stem away from the original plant and dig up the new plant.
It can be transplanted into the garden right away or placed in a container to grow some more roots.
Areas were eggplants are to be planted can be pre-treated with a complete fertilizer (10-30-10 at 1 to 1½ pounds per 100 square feet) or compost or manure (at 10 to 20 pounds per 100 square feet).
Additional nitrogen is needed at the time of flowering or initial fruit set. Well-composted manure or compost can be applied or use a chemical fertilizer. Too much nitrogen after fruiting, though, may cause normally purple fruit to be green.
Use 1 to 1½ pounds per 100 square feet of 10-30-10 or 10-20- 20 fertilizer applied in a 6-to 8-inch circle around the plants and 3 to 4 inches deep. Sulphate of ammonia can be applied as a top dressing using 1 to 2 tablespoons per plant applied 8 to 12 inches from the base.
Insects and Diseases
Though relatively free from many pests, eggplants are attacked by leafminers, rose beetles, aphids, flea beetles and mites. Bacterial wilt is a serious disease of eggplants in Hawaii. When the whole plant wilts but doesn’t recover after being watered, you may have this disease.
If you have experienced problems with bacterial wilt in your garden before, eggplants should not be planted there. It is a soil-borne disease and there is no organic or chemical control nor are there resistant varieties available.
It is wise to avoid planting eggplants where other members of the Solanaceae such as tomatoes, pepper or potatoes have been growing. A four- to five-year rotation of crops may help you avoid this disease in your garden.
The amount of fruit you get per plant will depend in the type you are growing and the conditions it is grown under. On average, though, expect eight to 14 fruits per plant with fruits ranging from ½ to 2 pounds.
Make sure you remove fruit religiously and don’t let any mature on the plant because this will reduce the yield considerably. Harvest your eggplants when they are the proper color for the type you are growing. This may be white, yellow, green, red, purple, black or mixtures of these.
The skin should be shiny and firm with the calyx and stem end green and fresh. Dull and wrinkled skin indicate excessive water loss and old age. Seeds should be immature and not fully developed. A good test is to press your finger into the fruit.
If the indentation springs back, the fruit is still immature enough to harvest and eat. If the indentation stays that way, the fruit is too mature and should be discarded unless seeds are being saved for a future crop. Cut, don’t pull the eggplant from the plant.
Pulling the fruit may cause either the fruit or the stem to rip, harming the product or allowing diseases to enter and harm the plant.
Eggplants can be stored for 10 to 14 days if they are kept cool and moist. They do not like to be kept too cold and may suffer from chilling injury. Ideally, store the fruit at 50° to 85° F with a relative humidity of 90 to 95 percent. Do not use cold water or ice.
Temperatures below 50° may cause pits to form on the surface of the fruit. If you have more fruit than you can use, it is possible to freeze eggplant. Peel the fruit, cut into 1/4- or 1/3-inch slices, or dice.
Immediately place the sections into cold water containing 1/4 teaspoon of salt per gallon of water. Blanch (quick-boil) for 4½ minutes in water with the same proportion of salt. Cool and package in layers separated by sheets of wax paper.