How can I help eggplants in a greenhouse to prevent them from falling off?

Bud and flower drop occurs more frequently in eggplants than in tomatoes or cucumbers. Plants react this way to a wide range of factors. Eggplants are demanding crops, and providing them with the necessary conditions in a greenhouse (and in most regions, eggplants can only be grown indoors) can be difficult.

Reasons for flower drop

Flower drop is most often associated with stress or a lack of pollination. In cases of stress, not only flowers but also ovaries may fall off.

Pollination

Although eggplants are self-pollinating, wind is required to transfer pollen from flower to flower, so pollination is an inevitable problem in a greenhouse. Unpollinated flowers fail to form ovaries, and the inflorescences fade, dry up, and fall off.

Furthermore, pollination may fail due to the pollen losing its ability to fertilize. This is due to unfavorable temperature conditions. Pollen becomes sterile or fails to germinate when it reaches the pistil at temperatures above 30°C or below 20°C.

Microclimate

Growing eggplants indoors requires careful monitoring of environmental parameters. Besides temperature, flower and bud loss can also be caused by:

• lack of light – the plant is very photophilous and requires direct sunlight for normal development, which can only be provided in a glass greenhouse;
• air humidity is more than 65% - eggplants have heavy pollen, when damp, it gains weight, and under its weight the flowers may break off;
• drafts when ventilating the greenhouse - inflorescences fall off en masse due to stress.

Nutrient deficiency or excess

Poor flowering and fruit set can be caused by improper fertilizing, poor or overly nutrient-rich soil. In this case, flowers fall off gradually, rather than en masse, without setting fruit.

Because crop rotation is impossible, greenhouse soil is susceptible to rapid depletion. On the other hand, for the same reason, the soil accumulates any nutrients that enter it in excess (those not consumed by the plants during the season). Overfertilization may go unnoticed if the excess is not critical, but if excessive amounts are applied year after year, the soil will eventually become toxic. Furthermore, under cover, nutrients are not washed out of the soil by precipitation.

Flower shedding without the formation of ovaries is likely in the following cases:

1. Boron deficiency. It is accompanied by chlorosis at the leaf tips and brittle leaves and stems. Severe deficiency causes stunted growth, leaf and root margins die, older leaves turn yellow and develop necrotic spots, flowers, fruits, and leaves become deformed, and growing points die.
2. Excess nitrogen. The bush expands, stems and leaves grow vigorously, flowers are few, and flowering may be delayed. Nitrogen overload is especially dangerous under conditions of low light and low temperatures—the surviving fruits will accumulate nitrates, which are dangerous to humans.
3. Excess micronutrients. Oversupply of any micronutrient (zinc, copper, and others) can cause eggplant blossom drop. Excessive boron fertilization can also be detrimental.

Spider mite

The activity of all pests and pathogens weakens plants and hinders the process of ovary formation, but the greatest threat to the crop during the flowering stage is the spider mite.

Other symptoms of damage:

• the appearance of small light areas on the leaves;
• gradually the entire leaf becomes covered with pinkish-white spots, acquiring a “marbled” color;
• on the back of the leaf, where the pests are localized, a thin web is formed;
• the affected leaves curl and wither;
• the growth of the bush slows down.

In warm weather, the pest multiplies rapidly, spreading throughout eggplant bushes. If left untreated, the insect can destroy the entire eggplant crop.

Violations of agricultural practices

Improper plant care can also cause flower drop. This reaction can be a result of:

• soil drying out – the crop is sensitive to moisture deficiency in the soil;
• Watering with cold water is a strong stress for plants, especially at high air temperatures; not only flowers, but also formed ovaries may fall off;
• high soil acidity - eggplants prefer neutral soils; in acidic soil, plants produce poor fruit sets and some flowers fall off.

Treatment measures

The first step in dealing with eggplant blossom drop for any reason, except immediately after boron fertilization, is to spray the plants with a 0.05% boric acid solution. This stimulates flowering and fruit set. Avoid applying boron to the roots; foliar feeding is most effective in this case.

It is equally important to eliminate all violations of growing and care conditions, as well as to inspect the plants, identifying possible pests, and, if found, to treat the planting.

1. If pollination problems occur, it is recommended to distribute pollen among the eggplant flowers manually using a brush, while simultaneously attracting honey-producing insects to the greenhouse (containers with sweet water, bunches of flowering onions, etc.).
2. If it is not possible to provide plants with a microclimate (temperature, humidity) favorable for pollination and ovary formation, treatment with ovary stimulants (“Bud”, “Ovary”) will help.
3. Eggplants that drop flowers due to prolonged rains (which means a severe lack of light and, possibly, low temperatures in the shelter) should be given foliar feeding with a solution of calcium nitrate (0.07%).
4. Weakened plants that have been subjected to any type of stress must be supported by treatment with immunomodulators (Ecosil, Epin-extra, and others).

Prevention

Saving an eggplant crop after massive flower drop is difficult. Providing for the needs of this capricious vegetable requires effort, but without proper care, the plants will simply take up space in the greenhouse.

Key points of care:

1. Periodic renewal of the top layer of soil in the greenhouse, liming procedure on acidic soils.
2. Maintain a 60 cm distance between eggplant plants to avoid unwanted shading. The distance between rows should be approximately 70 cm.
3. Maintaining the required temperature in the greenhouse for eggplant flowering is within the range of +22…+26°C.
4. During flowering, water the plants twice a week at a rate of 12 liters per square meter. Water should be between 25 and 30°C.
5. Greenhouse ventilation and air humidity control.
6. Regular but moderate pruning of bushes is essential. It's important to ensure light reaches the fruit, but leave enough leaves for normal photosynthesis. Otherwise, the plant won't be able to support the fruit harvest.

7. Proper fertilizing. During flowering, eggplants require twice as much phosphorus and potassium as during the growing season. Avoid applying nitrogen-containing fertilizers during this period; in particular, avoid using organic fertilizers.
8. Foliar feeding with boron (0.05%) and magnesium sulfate (0.01%) twice during flowering with a 10-day break.

These measures are usually sufficient for plants to bloom well and produce fruit. If the percentage of flowers that fall without setting fruit in an eggplant planting is no more than 40%, there's no cause for concern. This is a normal figure for this crop and doesn't indicate any developmental issues.