Growing Eggplant in Protected Cultivation

1. Where and why protected cultivation is used for eggplant

Eggplant (Solanum melongena L.) is a plant of southern origin. Its homeland is the warm regions of Southeast Asia (Kotov, Adritskaya, 2016). This crop is a true "sybarite" among vegetables: it requires a lot of heat, sun, and time to mature. That is precisely why, in regions with temperate and cool climates, as well as for obtaining extra-early produce, growing eggplant in protected cultivation becomes not just desirable but a necessary condition for success.

Why do gardeners and farmers "house" eggplants under cover?

1. Extending the growing season: Eggplant is a crop with a long growing season. From germination to the start of fruiting, early varieties take 85-100 days, while late varieties can take up to 150 days (Tarakanov, Mukhin, 2003). In the short summer conditions of the middle belt or Siberia, the plant simply does not have time to produce a full yield in open ground. Protected cultivation allows us to "trick" nature and give the eggplant the time it needs for growth and fruiting.

2. Protection from adverse weather conditions: Eggplant is extremely sensitive to temperature fluctuations.

• Heat: It is the most heat-loving crop in the Solanaceae family. The optimal temperature for its growth and fruiting is 22-30 °C. At temperatures below 15-17 °C, plant growth virtually stops, pollen becomes sterile, and fruit set drops (Kotov, Adritskaya, 2016; Rubatzky, Yamaguchi, 1997). Temperatures above 35 °C are also detrimental to pollination and fruit set.
• Frost: Eggplant does not tolerate frost at all. Even light frosts (0...-1 °C) can kill the plants. Covering reliably protects against returning spring cold snaps and early autumn frosts, allowing harvest to be extended into late autumn.
• Wind and drafts: Unlike tomatoes, eggplants do not like drafts. It is easier to create a calm, warm microclimate in a greenhouse.
• Obtaining earlier and higher yields: In protected cultivation, we can create ideal growing conditions starting from early spring. This allows us to plant seedlings several weeks earlier than in open ground and harvest significantly earlier. Fruits in a greenhouse are often larger and have a more attractive marketable appearance (Torikov, Sychev, 2018).
• Optimizing watering and nutrition: In a closed environment, it is easier to control soil and air humidity, as well as dosage of fertilizers, helping avoid many problems associated with overwatering or drying out.

Thus, growing in protected cultivation is the key to a stable and bountiful harvest of "little blue ones" even in regions where it seems impossible. In commercial vegetable growing, eggplants in winter greenhouses hold a worthy place, and for hobbyists and small-scale farmers, it is an opportunity to extend the fresh vegetable season and get the maximum return from their plants (Kotov, Adritskaya, 2016).

2. Types of protected structures for eggplant

Choosing the right cover is the first step to success. Various types of protected structures are suitable for eggplant, from the simplest to permanent ones. The choice depends on your goals, climate, and budget. All serve one purpose: to create a warm, humid, and protected microclimate for this heat-loving crop.

Let's look at the main options.

1. Heated winter greenhouses (permanent structures)

This is the pinnacle of protected cultivation. Such greenhouses have a permanent foundation and, as a rule, are covered with glass or polycarbonate. Their main distinguishing feature is the presence of a heating system.

• For whom and when: This option is for those who want to harvest eggplants year-round or at the earliest possible times (as early as February-March) (Torikov, Sychev, 2018). In commercial vegetable growing, this is the primary method. For a small farmer or hobby gardener, this is the most expensive but also the most reliable option.
• Features: In winter greenhouses, you can maintain optimal temperatures (22-28 °C during the day and 16-18 °C at night) even in the coldest months. For eggplants, these are ideal conditions, allowing hybrids to fully express their potential (Kotov, Adritskaya, 2016). It is convenient here to use drip irrigation and fertilization systems, as well as manage air humidity. Remember that eggplant, especially in a confined space, needs pollination, so bumblebees are often used to pollinate flowers in such greenhouses (Kotov, Adritskaya, 2016).

2. Spring (unheated) greenhouses and hotbeds

This is the most common type for hobby gardeners and small farmers. Such greenhouses are typically covered with polyethylene film (single or double layer) or polycarbonate. They do not have a heating system but accumulate solar heat well.

• For whom and when: An ideal choice for growing eggplants in regions with a temperate climate, where the main problems are returning spring frosts and a short summer. Seedlings are planted in such greenhouses later than in heated ones, but significantly earlier than in open ground (for example, in the central zone of Belarus — from May 5 to 10) (Autko et al., 2012).
• Features: The main advantage is the rapid warming of soil and air in spring. Film or polycarbonate protects plants from wind, rain, and nighttime cooling. However, on sunny days, the temperature in such a greenhouse can rise to critical levels (above 30-35 °C), so a ventilation system (vents, doors) is mandatory (Kotov, Adritskaya, 2016). Nighttime temperatures can drop, so during cool months, plants may require additional cover (e.g., spunbond) inside the greenhouse.

3. Tunnels and small-scale film covers (e.g., URP-20)

These are arches installed over a bed and covered with film or non-woven material. These are the simplest and most budget-friendly structures.

• For whom and when: An excellent option for obtaining early harvests on small plots. They protect well against light frosts and wind and also accelerate soil warming in early spring. However, in hot weather, such covers require frequent and thorough ventilation; otherwise, plants can "burn." They also limit plant height.
• Features: Eggplants are planted in tunnels when the threat of severe frosts has passed. With biofuel (horse or cow manure, straw), such covers work especially effectively, providing additional heating for the root system (Torikov, Sychev, 2018). Yields in such covers will be lower than in greenhouses, but they allow harvesting fruits 2-3 weeks earlier than in open ground.

4. Small-volume technology (hydroponics) — a modern approach

This is not quite a "structure" in the classical sense but rather a soilless growing method. Plants are placed in small containers or bags with a substrate (mineral wool, peat, perlite, coconut fiber) and receive nutrition through drip irrigation with special solutions.

• For whom and when: This method is gaining popularity in modern greenhouse operations and among advanced gardeners. It allows for maximum efficient use of greenhouse space and volume, as well as precise control over plant nutrition.
• Features: Small-volume hydroponics yields the highest and earliest harvest (Kotov, Adritskaya, 2016). It requires special equipment (solution tanks, drippers) and constant monitoring of pH and electrical conductivity (EC) of the nutrient solution (Torikov, Sychev, 2018). This method helps avoid soil-borne diseases but requires high cultivation standards and attention. For eggplants, hybrids with a compact root system and resistance to salinity are ideal (Kotov, Adritskaya, 2016).

Brief summary for choosing a structure:

The choice is yours, but remember: even the simplest film greenhouse or tunnel will significantly increase your chances of a bountiful eggplant harvest.

3. Features of soil and bed preparation in protected cultivation

Eggplant is a crop with a powerful but sensitive root system. Unlike tomato, it does not develop additional roots on the stem when hilled, so the quality and structure of the soil are crucial (Kotov, Adritskaya, 2016). In closed ground, where soil is used intensively and not naturally renewed, preparation becomes even more important.

What should the ideal soil for eggplant be like?

• Light and loose: Eggplant prefers light, well-drained soils. Heavy clay soils prone to compaction are unsuitable — they hinder air access to the roots and can cause them to rot (Autko et al., 2012).
• Fertile: This crop is very demanding in terms of nutrition. The soil must be rich in organic matter and contain all necessary macro- and microelements in an available form.
• Neutral or slightly acidic reaction: The optimal pH level for eggplant is 6.0–6.5 (Autko et al., 2012; Rubatzky, Yamaguchi, 1997). In acidic soils, plants are stunted, and nutrients (especially phosphorus and calcium) become less available.

Step-by-step soil preparation in a greenhouse or hotbed

The preparation process begins long before planting seedlings and includes several key stages.

1. Sanitary treatment and disinfection

This is a critically important step, especially if the greenhouse is not being used for the first time. In protected cultivation, pathogens (fusarium, late blight, gray mold) and pests (root-knot nematode, spider mite, whitefly) accumulate quickly (Kotov, Adritskaya, 2016).

• Removal of plant residues: In autumn or early spring, thoroughly remove all residues from previous crops, weeds, and mulch.
• Replacing or disinfecting the topsoil: The most radical method is to remove the top layer of soil (5-10 cm) and replace it with fresh soil. If this is not possible, the soil must be disinfected. In commercial greenhouses, steaming is used for this (Torikov, Sychev, 2018). In hobby conditions, you can use drenching with boiling water or a potassium permanganate solution, as well as biological products (e.g., "Fitosporin," "Trichodermin"). Remember that such products need to be applied well in advance so that the beneficial microflora has time to recover.

2. Creating a fertile soil mixture

Since we are talking about protected cultivation, the ideal option is to prepare a special soil mix that will best meet the requirements of eggplant. Main components for the mix (by volume):

• Sod soil (30-50%) — provides structure and retains moisture.
• Humus or well-rotted compost (20-30%) — the main source of organic nutrition and humus.
• Peat (30-50%) — loosens the soil, improves air exchange, and retains moisture. For eggplant, it is better to use lowland or transitional peat with a neutral reaction (Torikov, Sychev, 2018).
• Wood sawdust or chopped straw (up to 20%) — excellent loosening agents that also improve water-air regime (Autko et al., 2012). However, sawdust consumes nitrogen during decomposition, so they should be pre-soaked in a urea solution or composted.

Example recipe for a successful greenhouse mix (according to Torikov and Sychev, 2018):

• Peat (50%) + sod soil (30%) + manure compost (20%).

3. Fertilizer application — base dressing

Even before planting seedlings, the soil needs to be enriched with nutrients. Eggplant is characterized by a high demand for potassium and also requires sufficient amounts of nitrogen and phosphorus.

Organic fertilizers: In autumn or 2-3 weeks before planting, apply humus or compost at a rate of 5–8 kg per 1 m² (Autko et al., 2012). Fresh manure is best avoided for eggplant, as it can burn the roots and provoke diseases.

Mineral fertilizers: Approximate rates for application before planting (per 1 m²) (Autko et al., 2012):

• Nitrogen (ammonium nitrate) — 30–40 g
• Phosphorus (double superphosphate) — 30–40 g
• Potassium (potassium sulfate, not potassium chloride!) — 40–50 g
• Magnesium (magnesium sulfate) — 5–10 g, as eggplant is very sensitive to its deficiency (Autko et al., 2012).

Important: Chlorine-containing potassium fertilizers are contraindicated for eggplant (Kotov, Adritskaya, 2016). Use only potassium sulfate.

4. Forming beds and planting scheme

Proper bed organization ensures better soil heating, light, and air access for plants.

Bed height: In greenhouses with high humidity or a high water table, it is better to make raised beds (20–30 cm) to avoid water stagnation around the roots (Autko et al., 2012).

Bed width: Usually 70–90 cm for double-row planting. This ensures convenient access to the plants.

Planting scheme: For vigorous and medium-vigorous hybrids in protected cultivation, a double-row scheme is used:

• Wide row spacing (walkway): 90–100 cm
• Narrow row spacing (between rows in one bed): 50–60 cm
• Distance between plants in the row: 40–60 cm (Kotov, Adritskaya, 2016; Autko et al., 2012).

Final planting density for vigorous greenhouse hybrids is about 3–4 plants per 1 m² (Torikov, Sychev, 2018). Too dense planting will lead to shading, diseases, and small fruits.

Thus, thorough soil preparation and proper bed formation are the keys to ensuring your eggplants get everything they need for a strong start and will reward you with a bountiful harvest.

4. Transplanting seedlings into protected cultivation

Transplanting is always stressful for plants. For eggplant, with its sensitive root system, this stress can be particularly strong. Our task is to make the move from the nursery to the greenhouse as comfortable as possible so that the plants quickly establish and start growing.

When to transplant?

The main rule is do not rush. Eggplant is the most heat-loving crop among the Solanaceae. Planting dates are determined not by the calendar but by soil and air temperatures.

• Soil temperature: At planting time, the soil at a depth of 15–20 cm should have warmed to 18–20 °C (Autko et al., 2012). Cold soil (below 15 °C) severely inhibits growth and can cause root rot.
• Air temperature: Night temperatures should not fall below 15 °C (Kotov, Adritskaya, 2016). Frost is fatal for eggplants.

Approximate timing for different types of cover:

• In heated winter greenhouses: planting can begin as early as January-February.
• In spring unheated greenhouses (for the central zone): the optimal time is from May 5 to 10, after the threat of frost has passed (Autko et al., 2012; Tarakanov, Mukhin, 2003).
• In film tunnels and hotbeds: 1–2 weeks later than in greenhouses.

Preparing seedlings for transplanting

7–10 days before transplanting, start hardening off the seedlings. This helps the plants adapt to the harsher greenhouse conditions:

• Lower the air temperature by 3–5 °C during the day by opening vents or moving trays to a cooler location.
• Gradually increase the time the seedlings spend in direct sunlight to avoid sunburn.
• The day before planting, water the seedlings thoroughly — this makes them easier to remove from pots and preserves the root ball (Autko et al., 2012).

Seedling quality matters

Select only strong, healthy plants for transplanting. Ideal eggplant seedlings for a greenhouse should have (Autko et al., 2012):

• Age: 60–70 days (for early varieties in the middle belt) or 50–60 days (for later planting).
• Height: 20–30 cm.
• Number of true leaves: 6–8.
• Stem thickness: 0.6–0.8 cm.
• Initiation of flowering (budding) — a sign of readiness for planting.

The main rule of planting: do not bury the stem!

This is a critically important point that is often overlooked. Unlike tomatoes, eggplant does not develop additional adventitious roots on the stem (Kotov, Adritskaya, 2016).

• Plant the seedlings strictly vertically.
• Do not bury the root collar (the point where the stem transitions to the root) — this can lead to its rotting and the death of the plant (Kotov, Adritskaya, 2016).
• The pot with the seedling should be placed in the hole no deeper than 2–3 cm, or ¾ of its height if it is a peat pot, ensuring the root collar remains at soil level (Torikov, Sychev, 2018).

Planting technique

1. Preparing holes: Dig holes 2–3 cm deeper than the height of the pot. The distance between holes depends on the planting scheme. For vigorous hybrids in the greenhouse, it is 40–60 cm in the row.

2. Watering the holes: Water each hole generously with warm water (0.5–3 liters) (Autko et al., 2012). This creates a "mud cushion" for the roots, ensuring better contact with the soil.

3. Removing from the pot: Carefully remove the plant from the pot, trying to preserve the root ball as much as possible. If the seedling is in a peat pot, it can be planted together with the plant. Make sure the pot walls are broken (you can tear them) so roots can grow out freely.

4. Planting: Place the plant in the hole, fill with soil, and lightly firm it. The root collar should remain at ground level.

5. Mulching: Mulch the soil around the plant with dry peat, humus, or sawdust. This prevents crust formation, conserves moisture, and protects roots from overheating.

First days in the new "home"

In the first days after planting, create a gentle regime for the plants:

• Shading: If the weather is very sunny, shade the plants for 2–3 days with non-woven material or newspapers to help them withstand the transplant shock.
• Watering: Water moderately during the first week, but make sure the soil does not dry out.
• Temperature: For the first 1–2 days, to promote better establishment, maintain a temperature of 22–23 °C during the day and no lower than 18 °C at night (Kotov, Adritskaya, 2016). 2–3 days after planting, the plants are tied to a trellis (Autko et al., 2012).

Quick planting checklist:

Proper planting is an investment in the future harvest. Approach this stage with maximum attention, and the eggplants will reward you with healthy growth and abundant fruiting.

5. Microclimate management

In open ground, we depend on the whims of the weather. In a greenhouse, we become the creators of the weather ourselves. The gardener's task is to create a microclimate for the eggplant that allows it to unlock its genetic potential. This requires a balance between three main parameters: temperature, humidity, and ventilation.

Temperature — the main factor

Eggplant is the most heat-loving crop in the Solanaceae family (Kotov, Adritskaya, 2016). Its reaction to temperature is critical at all stages of development.

Optimal values: For active growth and fruiting, the ideal temperature regime is:

• Day (sunny weather): 25–28 °C
• Day (cloudy weather): 20–22 °C
• Night: 17–20 °C (Autko et al., 2012; Kotov, Adritskaya, 2016)

Critical thresholds:

• Below 15 °C: Plant growth and development slow down sharply. Pollination becomes impossible, pollen loses fertility, flowers and fruit set drop (Rubatzky, Yamaguchi, 1997; Autko et al., 2012).
• Below 13 °C: The root system virtually stops functioning. Prolonged exposure to low temperatures (10-12 °C) can cause plants to become diseased and die.
• Above 35 °C: This is the critical upper limit. In heat, pollen becomes sterile, fruit set does not occur, and fruits do not set. Moreover, flowers and young ovaries may drop (Tarakanov, Mukhin, 2003).

Air and soil humidity

Eggplant originates from humid subtropics, so it likes humid air and soil.

• Air humidity: The optimal range is 65–75% (Kotov, Adritskaya, 2016). When air is too dry (below 60%), pollination suffers: pollen dries out and cannot adhere to the stigma, flowers and fruit set drop.
• Soil humidity: Ideal soil moisture should be maintained at 75–80% of field capacity (FC) (Kotov, Adritskaya, 2016). This means the soil should be constantly moist but not waterlogged. Both drying out and overwatering are equally harmful.

Ventilation — the key to health

Ventilation solves two crucial tasks at once: regulating temperature and air humidity. Without proper ventilation, problems inevitably arise in the greenhouse.

• Combating overheating: On sunny days, even in spring, the temperature in a greenhouse can quickly rise above 35 °C. Ventilation (through vents and doors) is the only way to bring the temperature down and prevent flowers from dropping. Remember that eggplant, unlike tomato, does not like drafts, so it is better to open vents on the leeward side or ensure the airflow is not too strong.
• Disease prevention: It is in poorly ventilated greenhouses that eggplants most often suffer from gray mold, powdery mildew, and other fungal diseases (Kotov, Adritskaya, 2016). High air humidity combined with cool weather is an ideal environment for fungi. After each watering, the greenhouse must be ventilated to allow excess moisture to evaporate.

Practical recommendations for microclimate management

1. Daytime control:

• Install a thermometer and hygrometer (humidity meter) in the greenhouse. Monitor the readings.
• If the temperature rises above 28-30 °C, open all possible vents and doors. For greenhouses with automation, use thermal actuators that open vents when heated.
• If daytime temperatures remain consistently above 30 °C, light shading of the greenhouse can be applied. Special shading nets or simply throwing an old sheet over the roof are used for this. This is especially relevant in southern regions.

2. Nighttime control:

• Nighttime temperatures should not drop below 16–17 °C.
• On cold nights in unheated greenhouses, cover the plants with an additional layer of spunbond (agrofabric) directly over the plants, or install additional hoops with film inside the greenhouse.

3. Humidity:

• Water only in the morning so that excess moisture evaporates by evening and conditions for fungal growth are not created at night.
• Ventilate the greenhouse regularly after watering.
• To increase air humidity during dry and hot weather, you can refresh the paths with water or use fine mist spraying of the air (but not the plants) in the morning.

Table: Ideal microclimate for eggplant by growth phase

Important note: Sharp fluctuations in temperature and humidity are even more harmful to eggplant than stable extreme values. Try to avoid situations where the greenhouse heats up to 35 °C during the day and cools down to 12 °C at night. Stable microclimate is the key to plant health and a bountiful harvest.

6. Features of watering in protected cultivation

Eggplant is a crop with a powerful but relatively shallow root system. The bulk of the roots are located in the topsoil, so they cannot extract moisture from deep horizons like, for example, pumpkin roots (Rubatzky, Yamaguchi, 1997). At the same time, eggplant intensively transpires moisture through its large leaves. All this makes it extremely demanding of the water regime.

Why is proper watering the key to success?

1. Growth and development: Water is essential for all life processes — photosynthesis, nutrient transport, maintaining cell turgor (firmness). Lack of moisture immediately leads to leaf wilting, growth cessation, and consequently, flower and fruit drop (Tarakanov, Mukhin, 2003).

2. Fruit quality: With uneven watering (alternating drought with abundant watering), eggplant fruits often become bitter, coarse, and misshapen. Moreover, sharp fluctuations in humidity can cause fruit cracking.

3. Plant health: Excess moisture in the soil and, especially, in the air is a direct path to the development of fungal diseases such as gray mold, late blight, and root rots (Kotov, Adritskaya, 2016).

Basic rules for watering eggplants in a greenhouse

1. Water must be warm!

This is the most important rule. Watering with cold water (from a hose or well) is one of the main causes of diseases and growth retardation in eggplants (Autko et al., 2012). The water temperature for irrigation should be 23–25 °C, roughly equal to the air temperature in the greenhouse (Autko et al., 2012).

• How to achieve: Place a large container (barrel, tank) in the greenhouse and fill it with water in advance so it can warm up in the sun during the day. Use water from this container for watering.

2. Water at the root, not on the leaves

Eggplants, like many Solanaceae, do not like water getting on their leaves and stems (Kotov, Adritskaya, 2016). This provokes the development of fungal diseases (late blight, gray mold). Water strictly in the root zone, trying not to wet the plants.

• Best method: Drip irrigation. This is the ideal method for greenhouses. It provides a uniform, metered supply of water directly to the roots, does not over-humidify the air, and saves your time.
• Alternative: Watering from a watering can at the root, without using sprinklers.

3. Regularity and moderation — main principles

Eggplant does not tolerate either soil drying out or water stagnation. The soil in the greenhouse should be constantly moist, but not waterlogged.

Optimal humidity: Soil moisture should be maintained at 70–80% of field capacity (FC). Simply put, the soil should feel damp, but water should not stand on the surface or form puddles.

Watering frequency: It depends on the stage of plant development and the weather.

• On hot summer days (period of mass fruiting), water every 1–2 days.
• In cloudy and cool weather, reduce watering frequency to 1–2 times a week.
• Water consumption: On average, during active growth and flowering, 2–3 liters of water per plant per watering is needed. During mass fruiting, the watering volume can be increased to 3–5 liters per plant, as the formation of large fruits requires a lot of moisture (Kotov, Adritskaya, 2016). According to data for winter greenhouses, monthly water consumption can reach 150–160 l/m² (Kotov, Adritskaya, 2016).

4. Water in the morning, not in the evening

Watering done in the morning gives the plant a reserve of moisture for the whole day when evaporation is maximum. Additionally, the soil surface will have time to aerate during the day, and excess moisture will evaporate. Evening watering often leads to high night-time air humidity, which promotes disease development (Kotov, Adritskaya, 2016). After watering, be sure to ventilate the greenhouse to reduce air humidity.

5. Mulching — your helper

To reduce the number of waterings and prevent drying out, mulch the soil under the plants. Use as mulch:

• Humus or compost
• Straw
• Mown grass
• Special mulching film (black or two-color)

Mulch protects the soil from rapid evaporation, prevents weed growth, and helps maintain stable humidity. In protected cultivation, mulching is especially effective (Autko et al., 2012).

How to tell if the plant "asks for a drink"?

Pay attention to the condition of the leaves. If they begin to wilt slightly (lose turgor) in the middle of a hot day — it's a signal that it's time to water. If the leaves wilt in the morning when it's not hot yet — it means the soil is severely dry and urgently needs moisture.

What absolutely should not be done:

1. Water with cold water.

2. Waterlog the soil (excessive watering leads to root rot).

3. Allow drying out, as it is very difficult to restore plants after severe drought.

4. Water by overhead sprinkling (spraying on leaves) — this is a sure way to introduce fungal infection.

Simple reference table:

Remember that the figures given are just a guide. Always monitor the condition of the soil and plants. Ideal watering is one where the soil always remains moderately moist, and the eggplant leaves are firm and green.

7. Fertilizing in protected cultivation

Eggplant is one of the most demanding vegetables in terms of soil fertility. It doesn't just "eat"; it "absorbs" nutrients in large quantities. In terms of nutrient uptake, eggplant is close to tomato, but its root system is less powerful, making it dependent on regular and balanced feeding (Autko et al., 2012; Tarakanov, Mukhin, 2003).

What to know about eggplant nutrition?

1. Main macronutrients:

• Nitrogen (N): Critically important in the initial stages for building green mass. With its deficiency, plants look weak, leaves become smaller and turn yellow.
• Phosphorus (P): Ensures powerful root system development, promotes flowering and fruit set.
• Potassium (K): This is the main nutrient during the fruiting period. It is responsible for fruit quality: taste, size, color, and shelf life. Eggplant consumes almost as much potassium as nitrogen, and during fruiting — even more (Tarakanov, Mukhin, 2003).

2. Important micronutrients:

• Magnesium (Mg): Eggplant is very sensitive to magnesium deficiency. Its deficiency manifests as leaf chlorosis (yellowing), weakening the plant and reducing yield (Autko et al., 2012).
• Boron (B) and molybdenum (Mo): These micronutrients are critical for successful flowering and fruit set. Boron deficiency often leads to flower and fruit drop (Rubatzky, Yamaguchi, 1997).
• Iron (Fe): In alkaline soil, iron becomes unavailable, causing chlorosis of young leaves.

Main principle of fertilization: "Separate feeding"

Eggplant needs different nutrients at different stages of its life. Therefore, fertilization is divided into three phases.

1. Fertilizing after planting (active growth phase)

The first fertilization is carried out 10–14 days after transplanting, when the seedlings have established and started actively growing (Autko et al., 2012).

Goal: Stimulate growth and development of green mass.

Composition: Focus on nitrogen and phosphorus. The ideal option is a complete fertilizer with an equal NPK ratio or a slight predominance of nitrogen (e.g., 10-10-10 or 15-10-10). You can also use a solution of cow manure (1:10) or poultry manure (1:20), which contains a lot of nitrogen.

Recipe (per 10 liters of water):

• Ammonium nitrate — 10 g
• Superphosphate (double) — 15 g
• Potassium sulfate — 10 g

Application rate: 1–2 liters per plant.

2. Fertilizing during flowering and budding

The second fertilization is carried out when the first buds begin to appear. This is a critical moment, as it determines how many flowers and fruit sets will form (Autko et al., 2012).

Goal: Stimulate flowering and fruit set.

Composition: During this period, it is important to reduce the proportion of nitrogen to prevent the plant from "vegetating" excessively (going into foliage) and to increase the dose of phosphorus and potassium.

Recipe (per 10 liters of water):

• Ammonium nitrate — 8 g
• Superphosphate (double) — 20 g
• Potassium sulfate — 15 g

Application rate: 1–2 liters per plant.

3. Fertilizing during fruiting

The most important fertilizations are carried out during mass fruit formation and growth. Here, the main task is to provide the fruits with nutrition.

Goal: Improve fruit quality and size, extend fruiting.

Composition: Maximum potassium, moderate phosphorus, minimum nitrogen. Potassium is responsible for sugar content, taste, and skin firmness of the fruit.

Recipe (per 10 liters of water):

• Ammonium nitrate — 5–6 g
• Superphosphate (double) — 15 g
• Potassium sulfate — 20–25 g

Application rate: 2–3 liters per plant.

Foliar feeding (on leaves)

This is an effective way to quickly deliver micronutrients or help the plant in a stressful situation (cold, overheating, nutritional deficiency). Foliar feeds are well absorbed and act faster than root feeds.

When to use: When signs of chlorosis (leaf yellowing) appear, weak flowering, for disease prevention.

What to use:

• Complete fertilizers with micronutrients (e.g., "Uniflor-micro," "Kemira-Lux").
• Iron chelates — to eliminate chlorosis.
• Boric acid (1 g per 1 liter of water) — to improve flowering and fruit set.
• Humates — to increase plant immunity.

Rules: Spray in the morning or evening (on cloudy days, it can be done during the day) so that the solution does not dry out quickly and is well absorbed.

Important rules for fertilization in protected cultivation

1. "Better underfeed than overfeed": Excess fertilizer, especially nitrogen, causes "luxuriant growth" (excessive foliage at the expense of fruit), reduces disease resistance, and can lead to nitrate accumulation in the fruits.

2. Watering before fertilizing: Always water the plants with clean water first (1–2 hours before), then apply fertilizers. This protects the roots from burning.

3. Alternate root and foliar feeds: This approach gives the best results.

4. Monitor plant condition: Inspect the plants carefully. The leaves can tell you what they are lacking (see table below).

5. Consider the soil composition: If you added a lot of organic matter during planting, the dose of nitrogen fertilizers at the beginning of the season can be reduced by 30–40%.

Table: Diagnosis of nutrient deficiency in eggplant

Approximate fertilization schedule for the season (excluding starter fertilizer applied at planting):

Proper and timely fertilization is the key to obtaining large, uniform, and very tasty fruits. Don't skimp on feeding your eggplants, and they will reward you with a generous harvest.

8. Plant care in protected cultivation. Pollination and shaping

After planting the seedlings and providing them with the basic conditions, we move on to the main task — shaping the plant. Eggplant in protected cultivation, unlike in open ground, has enormous growth potential. Without proper management of this growth, we will get a jungle of foliage instead of a harvest of large fruits. In this chapter, we will cover three key operations: tying, shaping, and pollination.

1. Tying to the trellis

Unlike low-growing varieties for open ground, greenhouse eggplants, especially indeterminate (unlimited growth) hybrids, can reach a height of 1.5–2 m or more (Kotov, Adritskaya, 2016; Torikov, Sychev, 2018). Tying them is essential.

Why tie up?

1. Support: Eggplant stems, although powerful, can break under the weight of large fruits, especially at branching points.

2. Light exposure: Tied plants receive better sunlight, which positively affects fruit set and color.

3. Ventilation: The vertical arrangement of stems and removal of excess shoots improves air circulation, reducing the risk of fungal diseases.

4. Ease of care: Tied plants are easier to water, treat, and harvest.

How to tie up?

• Timing: The first tying is done 7–10 days after planting, once the plants have established (Autko et al., 2012).
• Method: Use soft twine (not fishing line!). Tie one end of the twine with a loose loop (figure-eight) around the base of the stem above the first fork. Secure the other end to the top wire of the trellis. As the stem grows, it should be periodically twisted around the twine.
• Important: Eggplant stems and shoots are more brittle than those of tomatoes, so work carefully to avoid breaking them (Torikov, Sychev, 2018).

2. Bush shaping: the architecture of the harvest

This is the most important and complex part of care. Eggplant in a greenhouse is formed into 2–3 stems (Kotov, Adritskaya, 2016; Autko et al., 2012). This allows for the maximum number of large, high-quality fruits.

Step-by-step shaping scheme:

1. Removing lower suckers and leaves: When the plant reaches a height of 30–40 cm, remove all suckers (side shoots) and leaves up to the first fork (branching of the main stem). This operation is called "blinding" (Torikov, Sychev, 2018). It improves lighting and ventilation in the lower part of the plant.

2. Selecting main stems: The main stem naturally divides into 2–3 strong shoots (fork) at the top. These will be the future main stems. We leave these for fruiting (Torikov, Sychev, 2018; Kotov, Adritskaya, 2016).

3. Suckering on the main stems: New side shoots (suckers) will appear on each of the retained main stems. These need to be removed, leaving only one shoot — the continuation of the main stem. Do this regularly, before the suckers grow to 5–7 cm. The earlier you remove them, the less nutrition they will take from the plant.

4. Fruit thinning: To allow the fruits to grow large, the number of fruit sets needs to be limited. On each main stem, 5–7 fruit sets are left (Kotov, Adritskaya, 2016). The remaining flowers and fruit sets are removed, especially small and weak ones. This rule is especially important for large-fruited hybrids. Fruits forming on suckers are also removed — they will be small and will only drain the plant's energy.

5. Pinching the growing point: When the stems reach the trellis (or about 1–1.5 months before the end of the season), pinch the tips of the main stems, leaving 2–3 leaves above the last flower cluster (Kotov, Adritskaya, 2016). This stops further growth and redirects all energy to ripening the already set fruits.

Important caution:

Never remove all leaves from the plant. Leaves are the "factory" for nutrition. Leave at least 2–3 upper leaves above each fruit. Remove old, yellowed, or diseased leaves gradually, no more than 2–3 at a time, to avoid weakening the plant.

3. Pollination in the greenhouse

In open ground, wind and pollinating insects do this work for us. In a greenhouse, natural pollination may be insufficient (Rubatzky, Yamaguchi, 1997). Without pollination, flowers drop, and fruits do not set. Therefore, helping the plants is essential.

• Natural pollination: On a sunny day, when the greenhouse is warm enough (25–30 °C), you can help the plants by simply shaking them. Tapping the trellis wire lightly or shaking the stems 2–3 times a week in the morning, when pollen is most viable, is sufficient. This helps the pollen fall from the stamens onto the pistil.
• Artificial pollination: For guaranteed results, you can pollinate manually using a brush. Transfer pollen from the stamens of one flower to the stigma of another (or the same) flower. This is a labor-intensive but reliable method.
• Bumblebees: The most effective method, especially for large greenhouses, is using bumblebee hives. Bumblebees are ideal pollinators for greenhouses; they work actively even in low light and temperature, unlike honeybees (Kotov, Adritskaya, 2016). One hive per 500–1000 m² of greenhouse completely solves the pollination problem.
• Fruit set stimulants: There are special preparations (e.g., "Ovary," "Bud") that stimulate fruit formation without pollination or with insufficient pollination. They are used according to the instructions as sprays.

Removing excess flowers

This is an important operation often overlooked. In each cluster of eggplant, 3–5 flowers typically form, but the plant cannot support all the fruit sets.

• Thinning: Leave 1–2 of the strongest flowers in the cluster, and carefully remove the rest. This allows the remaining fruits to grow large and uniform.

Summarizing the key care rules:

1. Tie up the plants to the trellis to avoid breakage.

2. Form the bush into 2–3 stems, removing all suckers on the main stems.

3. Remove all leaves and suckers below the first fork.

4. Regularly remove old and yellowed leaves.

5. Thin the fruit sets — leave 1–2 strong sets per cluster and no more than 5–7 sets per stem.

6. Pinch the growing points when the plant reaches the desired height.

7. Help the plant with pollination by shaking or using bumblebees.

Following these simple rules guarantees the formation of a strong, healthy bush that will bear fruit abundantly throughout the season.

9. Main pests and diseases in protected cultivation

Protected cultivation is an ideal environment for eggplant growth, but unfortunately, also for many pathogens and pests. Increased humidity, stable temperatures, and lack of natural ventilation promote their rapid spread. Therefore, the main protection strategy is prevention and early detection of problems.

Let's look at the most dangerous enemies of eggplant in the greenhouse and methods of controlling them.

Part 1. Diseases

In closed ground, eggplants are most often affected by fungal and viral diseases.

1. Fusarium wilt (Fusarium)

This is one of the most dangerous and common diseases in greenhouses (Kotov, Adritskaya, 2016). The fungus enters through the roots, clogs the vessels, and releases toxins.

Symptoms: The plant begins to wilt, starting with the lower leaves, then wilting spreads upward. Leaves turn yellow and curl. A cross-section of the stem shows dark brown vessels. Wilting can be one-sided (one branch wilts).

Causes: The fungus lives in the soil. High humidity, dense planting, temperature fluctuations, and excessive watering contribute to its development.

Control and prevention:

• Observing crop rotation in the greenhouse and replacing the soil.
• Choosing resistant hybrids (look for the F marking on seed packets — resistance to fusarium).
• Disinfecting the soil before planting (steaming, biological products).
• At the first signs: remove and burn the diseased plant. Drench the soil with a fungicide solution ("Trichodermin," "Fitosporin," "Fundazol").

2. Verticillium wilt (Verticillium)

Symptoms and control methods are very similar to fusarium. These diseases are often confused. Verticillium wilt more often manifests in cooler weather.

Symptoms: Lower leaves turn yellow at the edges, then turn brown and die. Wilting progresses more slowly than with fusarium.

Control: Similar to fusarium — prevention, healthy planting material, resistant hybrids.

3. Gray mold (Botrytis cinerea)

Especially dangerous in conditions of high humidity and sharp temperature fluctuations (Kotov, Adritskaya, 2016).

Symptoms: Gray-brown, rapidly expanding spots on stems, leaves, and fruits. A characteristic gray fluffy mold (fungal sporulation) appears on them. Affects all parts of the plant, often at wound sites.

Causes: Dense planting, poor ventilation, high air humidity, watering with cold water.

Control and prevention:

• Regular ventilation of the greenhouse.
• Watering only with warm water and at the root.
• Timely removal of suckers and lower leaves.
• When signs appear: treatment with preparations ("Skor," "Topsin-M," "Fitosporin"). Remove and burn affected parts of the plant.

4. Late blight (Phytophthora)

Although eggplant is affected by late blight less often than tomato, in the greenhouse this disease can be very dangerous.

Symptoms: Dark brown, rapidly expanding spots appear on the leaves. Dense brown spots appear on the fruits, which gradually rot.

Causes: Sharp fluctuations between day and night temperatures, high humidity, heavy dews (condensation on the film).

Control and prevention: Regular ventilation, treatment with copper-containing preparations ("Oxychom," "Hom," 1% Bordeaux mixture). Preventive treatments should begin before the disease spreads widely.

Part 2. Pests

In closed ground, pests reproduce almost year-round and quickly form colonies.

1. Spider mite (Tetranychus urticae)

One of the main enemies of eggplant in the greenhouse. In dry and warm air, it reproduces at a tremendous speed.

Symptoms: Small yellowish or white dots on the leaves (puncture sites). Then the leaves become covered with a fine web, turn yellow, dry out, and fall off. Mites live on the underside of leaves.

Causes: Hot and dry weather, insufficient watering.

Control and prevention:

• Increasing air humidity (spraying paths, but not plants!).
• Regular inspection of plants (especially the underside of leaves).
• In case of severe infestation: use acaricides ("Actellik," "Fitoverm," "Kleshchevit"). It is important to alternate preparations, as the mite quickly develops resistance.

2. Whitefly (Trialeurodes vaporariorum)

A small white insect resembling a tiny moth. Lives on the underside of leaves. Particularly dangerous in closed ground.

Symptoms: Sticky, shiny secretions (honeydew) appear on the leaves, on which sooty mold (black coating) then develops. Leaves turn yellow and wilt. When shaken, a cloud of small white flies rises from the plant.

Control and prevention:

• Regular ventilation and maintaining optimal humidity.
• Traps: Yellow sticky traps (attract whiteflies).
• Biological method: Using entomophages — the parasitic wasp Encarsia (Kotov, Adritskaya, 2016). This is the most effective and safe method.
• In case of severe infestation: treatment with insecticides ("Aktara," "Actellik").

3. Aphids (Aphididae)

Small green, black, or yellow insects. They live on young shoots and leaves, often in colonies.

Symptoms: Leaves curl, deform, become covered with sticky honeydew. Shoots become distorted, plant growth slows down. Aphids are carriers of viral diseases.

Control and prevention:

• Ventilation and maintaining humidity.
• For small numbers: wash off with soapy water.
• For mass infestation: insecticides ("Aktara," "Fitoverm," "Inta-Vir").

4. Thrips (Thrips)

Small, very mobile pests. Damage leaves and flowers by sucking sap.

Symptoms: Small silvery streaks and dots on leaves. Dark spots and deformation appear on flowers. Buds and fruit sets drop.

Control: Prevention, biological products ("Fitoverm"), acaricides.

Plant protection system in the greenhouse: strategy and tactics

1. Prevention is the foundation:

• Thoroughly remove plant residues in autumn.
• Replace or disinfect the topsoil.
• Use healthy seeds and high-quality seedlings.
• Observe crop rotation (do not plant eggplants after tomatoes, potatoes, or peppers).
• Regularly ventilate the greenhouse and avoid sharp fluctuations in temperature and humidity.

2. Regular inspection: Conduct weekly inspections of the plants, especially paying attention to the underside of the leaves. The earlier you notice a problem, the easier it will be to deal with it.

3. Biological method: Biological control methods are becoming increasingly common in greenhouses (Kotov, Adritskaya, 2016). This involves using beneficial insects (Encarsia against whitefly, Phytoseiulus against spider mite, Aphidimiza against aphids). This method is safe for humans and the environment.

4. Chemical method: Use chemical pesticides only as a last resort, strictly according to instructions, before flowering or after harvesting. Always observe the waiting period (the time between treatment and harvest).

Quick diagnostic table:

Remember: healthy and well-cared-for plants are much less susceptible to diseases and pests. Attention to the microclimate, balanced nutrition, and proper cultivation techniques are the best protection for your harvest.

10. Features of summer and autumn-winter cultivation

Eggplant is a long-day, warm-season crop. However, in protected cultivation, we can control the growing schedule, obtaining harvests not only in summer but also in the autumn-winter period. Care approaches vary depending on the season.

Part 1. Summer cultivation (June – September)

Summer is the time when eggplant can show its maximum potential. Long daylight hours, abundant sunlight, and warmth promote active growth and fruiting. However, summer is precisely when the main problems arise: overheating and drought.

Main features of summer care:

1. Overheating control: This is the main task in summer. The temperature in the greenhouse can easily rise above 35 °C, leading to pollen sterility, flower and fruit drop (Rubatzky, Yamaguchi, 1997; Kotov, Adritskaya, 2016).

• Ventilation: Open all vents and doors. On hot days, the greenhouse should be fully open. Use automatic ventilation systems (thermal actuators) if possible.
• Shading: If ventilation doesn't help, apply shading nets or throw an old sheet or spunbond over the roof. This is especially relevant for southern regions.
• Refreshing mists: In the hottest part of the day, in the morning, you can perform refreshing watering of the paths and air in the greenhouse (fine mist spraying). This increases air humidity and slightly lowers the temperature. Important: do not spray the plant leaves, only the air and paths.

2. Intensive watering: In summer, evaporation is maximal, so watering should be more frequent — every 1–2 days (Kotov, Adritskaya, 2016). Water consumption during mass fruiting can reach 4–6 liters per plant per day. Use warm, settled water.

3. Active shaping: In summer, plants grow very quickly. Remove suckers regularly, at least 1–2 times a week, so they don't outgrow (Kotov, Adritskaya, 2016). Don't forget to remove lower and old leaves to ensure good ventilation.

4. Pollination: In hot weather, pollination can be disrupted. Use all available methods: shaking plants, vibration, bumblebees. Perform shaking in the morning when it's not too hot yet.

5. Enhanced nutrition: In summer, plants consume maximum nutrients. Increase the dose of potassium fertilizers during fruiting — they are responsible for fruit quality and heat resistance. Carry out foliar feeds to quickly replenish micronutrient deficiencies (boron, magnesium).

Part 2. Autumn-winter cultivation (October – March)

During this period, the main enemies are short daylight hours, low light intensity, and cold. However, it is in autumn and winter that fresh eggplant prices are highest, and experienced gardeners use this period for additional income. In commercial greenhouses with supplementary lighting and heating, this is standard practice (Kotov, Adritskaya, 2016).

Main challenges of the autumn-winter period:

1. Lack of light: This is the main limiting factor. In low light, plants stretch, internodes lengthen, flowers and fruit sets drop.

• Solution: Use supplementary lighting systems (grow lights, HPS lamps, LED lights). The daylight period should be at least 12–14 hours.
• Correct variety selection: Use hybrids resistant to low light and adapted for extended production (e.g., F1 Britney, F1 Prego, F1 Jamilya) (Autko et al., 2012; Kotov, Adritskaya, 2016).

2. Cold and temperature fluctuations: In autumn and winter, temperatures in unheated greenhouses can fall below the acceptable 16–17 °C.

• Solution: Use heating (stoves, electric heaters, water heating systems) or, at a minimum, additional plant covering with spunbond inside the greenhouse.
• Important: Turn on heating especially at night to avoid sharp fluctuations between day and night temperatures. The optimal night minimum is 16–17 °C (Kotov, Adritskaya, 2016).

3. High humidity: In autumn, the air becomes more humid, which, combined with lower temperatures, creates ideal conditions for gray mold and other fungal diseases.

• Solution: Regular ventilation during the day, even in winter (during warm hours). Reduce watering.

4. Adjusting watering: In autumn and winter, plants consume less water as evaporation is low. Water less frequently — 1–2 times a week, but ensure the soil does not dry out completely. Use only warm water.

5. Adjusting nutrition: During periods of low light, reduce the dose of nitrogen fertilizers (to avoid provoking "luxuriant growth" and stretching), but increase the proportion of potassium — it improves disease resistance and promotes fruit set.

Comparative care table by season:

Variety recommendations for different seasons:

• For summer production: Any zoned varieties and hybrids resistant to heat are suitable. For example, F1 Clorinda, F1 White Night, F1 Bagira.
• For autumn-winter production: Choose special hybrids adapted to low light conditions, with vigorous growth and high fruit set. For example, F1 Britney, F1 Prego, F1 Jamilya, F1 Amethyst (Autko et al., 2012). Pay attention to disease resistance — this is especially important in the autumn-winter period.

Thus, competent microclimate management and adjusting care according to the season allow for stable eggplant yields in the greenhouse almost all year round.

11. Features of harvesting in protected cultivation

Harvesting eggplants is a process that requires attention and care. Unlike tomatoes, which can hang on the bush until fully ripe, eggplant needs to be picked at a strictly defined stage of maturity. Being even a few days late can spoil the taste and texture of the fruit.

When to harvest eggplants: the technical maturity stage

Unlike biological maturity (when seeds are fully ripe and the fruit becomes bitter and coarse), eggplants are harvested at the technical maturity stage (Kotov, Adritskaya, 2016; Autko et al., 2012). This is the period when the fruit has reached the size characteristic of the variety, but the seeds inside are still soft and light, and the flesh is juicy and tender.

Signs of technical maturity:

1. Size: The fruit has reached the size characteristic of the variety (length 10–20 cm, diameter 5–10 cm, weight 200–600 g depending on the hybrid).

2. Color: The fruit has acquired the color characteristic of the variety (dark purple, black, white, yellow, striped, etc.), but it is not yet dull.

3. Gloss: The most important characteristic! A fruit at technical maturity has a bright, glossy shine. Once the shine disappears and the surface becomes matte, the fruit is overripe and has lost its flavor.

4. Texture: When pressed with a finger, the fruit should be firm but not hard. If the indentation does not recover, the fruit is overripe.

5. Internal condition: Seeds are light, soft, and not fully formed. Flesh is white or slightly creamy, without bitterness.

How to harvest eggplants correctly?

This process requires caution to avoid damaging the plant and reducing future yields.

1. Timing: Harvest begins 25–35 days after flowering, when the fruits have reached the signs mentioned above (Rubatzky, Yamaguchi, 1997). The harvesting period in a greenhouse usually lasts from mid-summer until autumn frosts (in heated greenhouses — year-round).

2. Tool: Never pull the fruit off by hand! This can damage the stem and the plant. Use sharp secateurs or a knife (Autko et al., 2012).

3. Cutting technique: Cut the fruit together with the calyx (stem), leaving 1–2 cm of the stem. This extends the shelf life and prevents rot development. Cut carefully to avoid damaging neighboring fruits and shoots (Kotov, Adritskaya, 2016).

4. Regularity: Harvest fruits 1–2 times a week during mass fruiting (Kotov, Adritskaya, 2016). The more often you cut fruits, the more new sets the plant can form, and the higher the total yield will be.

5. Time of day: The best time for harvesting is early morning, when the fruits are still cool and firm. This improves their keeping quality (Kotov, Adritskaya, 2016).

Why is it important to harvest on time?

1. Taste and quality: Overripe fruits become bitter, coarse, with hard dark seeds. They are almost inedible.

2. Yield: If overripe fruits are left on the plant, it considers the "task complete" and stops forming new flowers and fruit sets. Timely harvesting stimulates new flowering.

3. Plant health: Overripe fruits often start to rot on the bush, becoming a source of infection for the whole plant.

What to do with overgrown fruits?

If you missed the moment and the fruit lost its shine and became brown or matte, it is better to remove it. These fruits are not suitable for eating but can be used for seed production (if the plant is not an F1 hybrid). Usually, they are simply cut off and discarded to avoid draining the plant's energy.

Harvesting features at different times of the year:

• Summer: Harvest regularly, at least twice a week. In hot weather, fruits ripen faster.
• Autumn: At the end of the season, before frost, all remaining fruits can be harvested. They may be smaller, but mostly at technical maturity. They can be used for short-term storage or processing.
• Heated greenhouses: In commercial greenhouses with supplementary lighting and heating, harvesting can continue almost all year round (Kotov, Adritskaya, 2016).

Quick harvesting checklist for eggplants:

Short-term storage of the harvest

Harvested eggplants are very delicate fruits. They should not be stored long at room temperature — they quickly lose moisture and become flabby.

• Optimal conditions: Store at 10–12 °C and high humidity (about 90%) (Rubatzky, Yamaguchi, 1997). Under these conditions, they can last up to 1–2 weeks.
• Do not store in the refrigerator: At temperatures below 7–8 °C, eggplants suffer chilling injury — they develop spots, become watery, and spoil quickly (Rubatzky, Yamaguchi, 1997).
• Use immediately: The best way to enjoy the taste of eggplant is to eat it on the day of harvest.

Thus, proper and timely harvesting is the final but very important chord in your work. It will allow you to enjoy tasty and healthy fruits and also extend the fruiting period of your plants.

12. Problems in protected cultivation and their solutions

Growing eggplants in a greenhouse is a fascinating but sometimes challenging process. Even experienced gardeners face various problems. It's important not to panic but to be able to quickly diagnose the cause and make the right decisions. In this chapter, we have gathered the most typical problems and provided practical tips for solving them.

1. Flower and fruit set drop

This is the most common problem when growing eggplants in a greenhouse. The reasons can vary.

Causes and solutions:

2. Fruits grow small or deformed

This signals that the plant is lacking something, or there are too many fruit sets.

Causes and solutions:

3. Leaves turn yellow and drop

This can be a natural process (aging) or a symptom of a problem.

Causes and solutions:

4. Pale, white, or yellow spots on leaves

This is often related to sunburn or improper watering.

Causes and solutions:

5. Plants stretch (become "leggy" and weak)

This phenomenon often occurs in autumn and winter due to lack of light or excess heat.

Causes and solutions:

6. Fruits are bitter

Bitterness in fruits can be related to physiological reasons or cultivation errors.

Causes and solutions:

7. Slow growth, general plant depression

This problem can be complex.

Causes and solutions:

Main principle: prevention is better than cure

Most problems can be prevented by following the basic rules of cultivation techniques:

1. Correct variety/hybrid selection: Consider resistance to diseases and the specifics of your region.

2. High-quality planting material: Use healthy seeds and seedlings.

3. Observing crop rotation: Do not plant eggplants after other Solanaceae.

4. Regular inspections: Inspect plants weekly to notice problems in time.

5. Timely harvesting: Do not allow fruits to overripen.

Remember: a careful and attentive approach is the best protection for your harvest.

13. Mistakes in growing in protected cultivation

Even experienced gardeners are not immune to mistakes. Eggplant is a demanding crop, and any deviation from the rules can cost the harvest. We have compiled the 10 most common mistakes so you can avoid them.

Mistake #1: Planting in cold soil

This is perhaps the most important and damaging mistake. Many rush to plant seedlings as soon as warm weather sets in, forgetting that the soil in the greenhouse is still cold.

• Consequences: Eggplant roots stop functioning at temperatures below 14–15 °C. The plant does not grow, "sits" in place, and weakens. In cold and wet soil, root rots (Fusarium, Verticillium) develop quickly (Kotov, Adritskaya, 2016; Autko et al., 2012).
• Solution: Always check the soil temperature at a depth of 15–20 cm. It should be at least 18 °C. Use warm beds, biofuel (manure, compost), or soil heating before planting (Autko et al., 2012).

Mistake #2: Planting seedlings with the root collar buried

Many gardeners, out of habit, plant eggplants the same way as tomatoes — burying the stem.

• Consequences: Unlike tomatoes, eggplant does not develop additional adventitious roots on the stem (Kotov, Adritskaya, 2016). Burying the root collar leads to its rotting, growth retardation, and plant death.
• Solution: Plant eggplants strictly vertically, without burying the root collar. The pot should be placed no deeper than 2–3 cm, or ¾ of its height if it's a peat pot (Torikov, Sychev, 2018).

Mistake #3: Watering with cold water

Water from a hose or well has a temperature of 8–10 °C. Watering with such water is a severe stress for eggplant.

• Consequences: Cold water causes "shock" to the root system, leads to flower and fruit drop, development of fungal diseases, and growth retardation (Autko et al., 2012).
• Solution: Always use only warm water (23–25 °C) for watering. Install a container (barrel, tank) in the greenhouse for settling and warming water (Autko et al., 2012).

Mistake #4: Ignoring bush shaping ("letting it run wild")

If you don't shape the eggplant in the greenhouse, it turns into an impenetrable thicket where fruits become smaller, and diseases and pests thrive.

• Consequences: Overcrowding, poor ventilation, lack of light, small and deformed fruits, high risk of diseases (Kotov, Adritskaya, 2016).
• Solution: Regularly form the bush into 2–3 stems, remove suckers, lower and old leaves (Kotov, Adritskaya, 2016; Torikov, Sychev, 2018).

Mistake #5: Excess nitrogen fertilization ("luxuriant growth")

This is a classic mistake of beginner gardeners: the more nitrogen, the better. But this works only up to a certain limit.

• Consequences: Excess nitrogen leads to rapid growth of green mass ("luxuriant growth") at the expense of flowering and fruiting. Plants become loose, their disease resistance decreases, and fruits accumulate nitrates (Tarakanov, Mukhin, 2003).
• Solution: Maintain the NPK balance. During flowering and fruiting, reduce the proportion of nitrogen and increase the proportion of potassium and phosphorus.

Mistake #6: Overwatering ("flooding")

Eggplants love moisture but not waterlogging. Water stagnation around the roots is harmful.

• Consequences: Roots suffocate and begin to rot. Root rots and other fungal diseases develop. Plants wilt, turn yellow, and die.
• Solution: Water moderately but regularly. The soil should be moist but without puddles. Ensure good drainage. After watering, be sure to ventilate the greenhouse.

Mistake #7: Too high planting density

In an attempt to get more yield from a small area, gardeners often plant eggplants too closely.

• Consequences: Plants compete for light, water, and nutrition. This leads to stretching, poor ventilation, reduced yield, and increased disease risk (Kotov, Adritskaya, 2016).
• Solution: Follow the optimal planting scheme: 3–4 plants per 1 m² for vigorous hybrids (Kotov, Adritskaya, 2016; Torikov, Sychev, 2018).

Mistake #8: Neglecting pollination in the greenhouse

There is no wind or insects in a greenhouse, so pollination may be insufficient.

• Consequences: Flower and fruit drop, formation of small and deformed fruits, or their complete absence (Rubatzky, Yamaguchi, 1997).
• Solution: Regularly shake the plants (2–3 times a week) or use bumblebees (the most effective method) (Kotov, Adritskaya, 2016).

Mistake #9: Untimely harvesting ("overkeeping" fruits on the bush)

Very often, gardeners leave the first, especially large, fruits on the bush "for beauty" or to let them "grow more."

• Consequences: Overripe fruits become bitter, coarse, and lose flavor. Moreover, the plant "thinks" it has already fulfilled its task and slows down the formation of new flowers and fruit sets (Kotov, Adritskaya, 2016).
• Solution: Harvest fruits at the technical maturity stage (glossy shine, size characteristic of the variety). Harvest regularly, 1–2 times a week.

Mistake #10: Insufficient ventilation of the greenhouse

A closed, "stuffy" greenhouse is an ideal environment for diseases.

• Consequences: High humidity and lack of air circulation lead to massive development of gray mold, late blight, and other fungal diseases (Kotov, Adritskaya, 2016).
• Solution: Ventilate the greenhouse regularly, especially after watering. In hot weather, the greenhouse should be open as much as possible. Use automatic ventilation systems.

Summary checklist: what NOT to do with eggplant in the greenhouse

By avoiding these mistakes and following the rules of cultivation techniques, you can obtain stable and abundant yields of tasty and healthy eggplants even in the most challenging climatic conditions. Good luck!

This concludes the full cycle of articles on growing eggplant in protected cultivation. If you would like to add any sections or clarify details, I am always ready to help. Happy harvesting!

References

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6. Ториков, В.Е., Сычев, С.М. (2018). ‘Овощные культуры защищённого грунта [Protected-ground vegetable crops]’, in Овощеводство [Vegetable growing]. Санкт-Петербург: Лань, pp. 11-20.