Aubergines need a lot of heat, but with a few tricks they can be grown in temperate climates. Here is a guide for growing eggplant, from planting to harvest.
The eggplant (Solanum melongena) has many names among amateur gardeners: It is also called the egg tree, egg fruit, egg plant, guinea squash, or aubergine. Like tomatoes, peppers and potatoes, eggplant is a member of the nightshade family (Solanaceae). The heat-loving vegetable comes in a variety of shapes and colors. The name “eggplant” is derived from the white, egg-shaped varieties grown primarily in Africa and Southeast Asia. The eggplant originated in Asia, specifically the East Indies, where it was cultivated as early as 1000 BC. The fruit probably reached the European mainland with the Arabs in the 12th and 13th centuries via Spain. Today, China, Japan, Turkey and Spain are the main areas of cultivation.
Appearance and growth of the eggplant
Eggplant is an annual vegetable. With its velvety hairy, large and oval leaves, purple bell-shaped flowers with yellow stamens and shiny fruits up to 30 centimeters (12 in) long, the eggplant is definitely an ornamental vegetable. This attractive vegetable plant grows bushy and reaches a height of 60 to 120 centimeters (24 to 48 in).
Location and soil
The aubergine, which requires warmth, can be grown outdoors in temperate climates only under very favorable conditions, namely in wine-growing areas and in places with a favorable microclimate, for example in a wind-protected place in front of a south-facing house wall. The aubergine thrives in loose, humus-rich soils that have previously been generously enriched with mature compost. However, since growth stagnation can occur at temperatures as low as 15 °C / 59 °F, cultivation in a greenhouse or foil greenhouse is clearly the more common method in these parts of the world.
The optimum temperature for growing eggplant in a greenhouse is 25 C° (77 °F). The plants do not tolerate high humidity very well, so regular ventilation is essential.
Crop rotation and mixed cultivation
Plant eggplant only once every four years in the same bed. Good preceding crops are beans and other legumes.
Sow aubergines at the end of January if possible. However, even with early planting, the harvest date can be moved up only slightly. They are sown in the same way as tomatoes. As the seeds of the eggplant are very good at germinating, one seed per pot is enough. Cover thinly with potting soil and water well. Indoors, the seeds will germinate best under a transparent cover on a warm, bright windowsill. Unlike tomatoes, however, eggplant takes two to four weeks to germinate, and that’s at a constant temperature of 22 to 24 °C (72 to 75 °F). So don’t rush to compost the contents of the pot because you think the seeds won’t germinate: It just takes time.
The seedlings of the eggplant are planted from the beginning of May in the beds of the greenhouse or foil house. The planting distance should be at least 60 x 60 centimeters (24 x 24 in), so that the shoots with their large leaves have enough room to spread. It is best to place a support rod in the soil at the time of planting, otherwise the shoots will later bend under the weight of the egg fruits or sink to the ground.
Caring for Eggplant
Fertilize eggplant several times during the growing season, but in slightly smaller amounts than tomatoes. When the seedlings have formed the first four true leaves, give them a liquid organic vegetable fertilizer. The bed in the greenhouse is enriched with about three liters of mature compost per square meter (11 sq.ft.) before planting the seedlings, then a little more horn meal or a mixture of seaweed lime and rock flour is sprinkled around each plant and the fertilizer is worked shallowly into the topsoil. Until the end of August, you can fertilize several times in smaller doses, for example with stinging nettle manure or comfrey manure. Both have a positive effect on the taste of the fruit.
Regular watering is especially important because aubergines evaporate a lot of water through their large leaves. Prolonged drought stress leads to loss of flowers and smaller fruit. The immediate root zone of the plants can be mulched with a thin layer of lawn clippings, for example, to reduce soil evaporation. If the side shoots become too long, you can simply cut them off at any point just behind a leaf. However, it is better to guide them upwards with additional stakes.
Occasionally it is advisable to remove part of the fruit set so that the remaining fruit will develop better and grow larger. If you grow only three shoots with two fruits each, you can get a better fruit set. However, hobby gardeners have different experiences on this point.
Harvest and use
Do not harvest your eggplant until the skin is fully colored and shiny blackish purple. Since they need long summer days to ripen, don’t expect a significant crop until late July or early August. However, do not wait too long to harvest, as overripe fruits become spongy and lose flavor. Another reliable sign of freshness are light green, not brown sepals. If you want to store eggplants, they can be kept for about a week wrapped in foil at about eight °C (46 °F).
The fruit of the aubergine develops its fine flavor only when baked, boiled or fried. You can also grill eggplants, marinating them in a spicy oil, for example. To enjoy the harvest longer, you can freeze eggplants or pickle them.
Pests and diseases of eggplant
Eggplant is relatively immune to diseases and pests. It is occasionally attacked by aphids, but these are easily controlled by spraying with water when infestation pressure is low. Whiteflies are more common in the greenhouse. Install yellow boards between plants to control the infestation and use beneficial insects such as ichneumon wasps for natural control. Gray mold is the most common fungal disease of eggplants. However, by keeping the foliage as dry as possible and airing the greenhouse regularly, infestations can usually be prevented.