Physiological disorders

Important Distinction from Nutrient Deficiency

Physiological disorders have an important feature: they are not always related to a low amount of a particular element in the soil. Often, the problem lies in conditions that prevent the plant from absorbing nutrients, even when they are present in sufficient quantities. For example, excess potassium can hinder the uptake of calcium and magnesium, while drought or waterlogging disrupts the absorption of elements by the roots (Dixon, 2007; Kotov and Adritskaya, 2016).

When is the problem reversible, and when is it not?

• If you notice the problem in time and correct its cause, the plant often recovers. For instance, adjusting the watering can stop cabbage heads from cracking.
• However, some changes are irreversible. For example, if a loose head has already formed, it will not become dense. In such cases, yield loss is inevitable, but it can be prevented in the future (Nonnecke, 1989).

Example: If a head has already cracked due to a sudden watering after a drought, the cracks will not heal. But understanding the cause will help you organize watering in the next season to avoid the problem (Welbaum, 2015).

Understanding these mechanisms is key to successfully growing cabbage. Knowing what went wrong allows you to quickly adjust your actions and save the crop.

2.1. Heat (Temperature Above Optimal)

Cabbage is a cool-weather crop. The optimal temperature for its growth and development is 15–18 °C during the day and 10–15 °C at night (Nonnecke, 1989; Welbaum, 2015). When temperatures consistently exceed 25 °C for a prolonged period, the plant switches from vegetative growth to reproductive growth: instead of producing leaves and forming a head, it starts to bolt, leaves become coarse, and head set is delayed or stops completely (Dixon, 2007; Autko et al., 2012).

Why does this happen?

At high temperatures, respiration increases, and the plant consumes more energy than it accumulates. Furthermore, heat disrupts the hormonal balance: the synthesis of auxins, necessary for leaf curling, decreases. As a result, the inner leaves do not curl inward, and the head does not form.

What to do?

• Choose heat-tolerant varieties and hybrids (e.g., some varieties for southern regions resistant to bolting).
• Plant cabbage so that the head-setting period falls during cooler months — early spring or autumn.
• Use shade nets or plant cabbage between rows of tall crops to protect it from the midday sun.

2.2. Long Day (Photoperiod)

Cabbage is a long-day plant. This means it requires a day length of more than 14–16 hours to transition to flowering. In northern regions, where summer days are long, the plant may "decide" it is time to flower and channel all resources into producing a flower stalk instead of forming a head. This is especially noticeable in varieties prone to bolting (Welbaum, 2015; Wien and Stützel, 2020).

Why does this happen?

Phytochrome, a light-sensitive protein in the plant, responds to day length. When days become long, a cascade of genetic programs aimed at flowering is triggered. If the plant has already passed the juvenile phase and accumulated enough cold hours, it may flower without forming a head.

What to do?

• For spring sowing, choose early-maturing, day-length-neutral varieties.
• In northern regions, practice the transplant method with planting in the ground when nights are still cool and days are not too long.
• In open ground, you can use cover material to create an artificial short day early in the growth period.

2.3. Excess Nitrogen

Nitrogen is the main element for building vegetative mass. However, its excess (especially against a background of potassium and phosphorus deficiency) causes vigorous leaf and stem growth at the expense of head formation. The head becomes loose and sometimes may not set at all (Nonnecke, 1989; Kotov and Adritskaya, 2016).

Why does this happen?

Excess nitrogen stimulates the synthesis of gibberellins — hormones responsible for stem elongation and vegetative organ growth. At the same time, it suppresses the formation of auxins necessary for leaf curling. The plant "luxuriates": leaves become large, dark green, brittle, and the central bud does not transition to the head-formation phase.

What to do?

• Maintain a balanced NPK ratio. For cabbage, an optimal N : P₂O₅ : K₂O ratio is approximately 1 : 0.8 : 1.2 (Autko et al., 2012).
• Apply nitrogen in split doses: the first part before planting, the second in the 4–6 leaf stage, and the third at the beginning of head set.
• Use organic fertilizers (well-rotted manure, compost) — they act more slowly and are less likely to cause nitrogen overfeeding.

2.4. Overcrowding

When planted too densely, plants compete for light, water, and nutrients. As a result, they stretch, produce small leaves, and cannot form a full head. Optimal density depends on the variety: early-maturing — 50–60 thousand plants/ha, late-maturing — 25–35 thousand (Kotov and Adritskaya, 2016).

Why does this happen?

In dense stands, each plant receives less light, especially in the lower part. This suppresses photosynthesis, and the plant directs resources to stem elongation upward to "outcompete" neighbors, rather than expanding the rosette and setting a head. Additionally, in shade, the leaves do not receive the signal to curl.

What to do?

• Follow recommended planting patterns. For example, for early varieties: 60 × 40 cm (about 40 thousand/ha), for late varieties: 70 × 50 cm (about 28 thousand/ha).
• When direct sowing, perform thinning at the 2–3 true leaf stage.
• Use varieties with compact rosettes if space is limited.

2.5. Stress (Drought, Waterlogging, Transplanting)

Any stress — be it lack of moisture, excessive watering, a sudden cold snap, or root damage during transplanting — can halt cabbage growth and trigger premature flowering. Stress during the juvenile phase is particularly dangerous when the plant has not yet accumulated enough leaf mass (Welbaum, 2015; Dixon, 2007).

Why does this happen?

Under stress, the plant releases ethylene and abscisic acid — hormones that suppress growth and accelerate aging. If stress is prolonged, the plant "decides" that the vegetative period is ending and switches to the reproductive program — it throws out a flower stalk without forming a head. This is especially common when transplanting hardened seedlings into too warm or too cold soil.

What to do?

• Water cabbage regularly, maintaining soil moisture at 70–80% of full water-holding capacity. During drought, watering is critical.
• Mulch the soil (straw, peat, mowed grass) to conserve moisture and protect roots from overheating.
• Transplant seedlings at the optimal time, when the threat of frost has passed and the soil has warmed to 8–10 °C. Harden seedlings gradually to avoid shock.

Key Takeaway:

If cabbage does not set a head — first check the temperature, lighting, fertilization, density, and stress factors. Usually, adjusting one or two parameters is enough for the plant to resume normal growth. However, remember: if the juvenile phase has already passed and the head has not begun to form, it is too late to catch up — it is better to focus on the next season by choosing the right variety and timing.

In the next chapter, we will discuss why a head may turn out loose — even if it did set.

3.1. Overheating During Head Setting and Filling

Cabbage forms a tight head only at moderate temperatures. If, during the active growth of inner leaves (usually 3–4 weeks before harvest), the average daily temperature exceeds 22 °C, the leaves grow faster than they can curl inward. They expand outward, making the head "shaggy" and loose (Nonnecke, 1989; Wien and Stützel, 2020).

Why does this happen?

At high temperatures, the rate of cell division increases, but their ability for directional growth decreases. The polarity of the leaf blade is disrupted: the leaf does not curl but continues to grow straight, forming so-called "rosette" leaves inside the head. Furthermore, in heat, respiration accelerates, and the plant does not accumulate enough dry matter to form a dense structure.

What to do?

• Choose varieties resistant to heat and "non-clinging" (e.g., late hybrids that set heads in late summer when the heat subsides).
• If heat arrives during the filling period, shade the planting (netting, spunbond) or plant cabbage in partial shade to reduce temperature around the head.
• Water generously in the morning and evening — evaporation from the leaves helps cool the plant.

3.2. Unstable Watering: Too Dry, Then Too Wet

Cabbage is very sensitive to fluctuations in soil moisture. Abrupt transitions from drought to heavy watering or prolonged rains disrupt the growth of inner leaves. During dry periods, leaf growth slows and they become smaller, but after watering, rapid growth begins, not inside the head but outside — the head "opens up" and loses density (Dixon, 2007; Kotov and Adritskaya, 2016).

Why does this happen?

The plant regulates cell turgor (water pressure). Under moisture deficiency, leaves lose elasticity and cannot pack tightly. When moisture is excessive, cells swell quickly, but since the inner leaves formed under drought conditions, they cannot fill the space inside the head. This creates voids, making the head loose.

What to do?

• Water cabbage evenly, avoiding long pauses. Watering rate — 1–2 times a week, 25–30 liters per 1 m² (more often in hot weather).
• Mulch the soil with a 5–7 cm layer (straw, mowed grass, peat). This smooths out moisture fluctuations and protects roots from overheating.
• During rainy periods, if heads have already started filling, you can artificially restrict water intake by making drainage ditches.

3.3. Excess Nitrogen During Head Formation

In the previous chapter, we mentioned that excess nitrogen prevents head setting. But even if a head has started to form, nitrogen overfeeding continues to harm: leaves grow too fast and become watery, and inner leaves do not have time to close. The head turns out large but "hollow" inside, with a wide stalk and many outer leaves (Nonnecke, 1989; Autko et al., 2012).

Why does this happen?

Nitrogen stimulates cell division but does not promote their compaction. Instead, it accelerates the growth of the stem (stalk) and petioles, not the leaf blade. As a result, the inner stalk becomes long, and the leaves cannot tightly wrap around it. Additionally, excess nitrogen reduces sugar and dry matter accumulation, making the head watery and loose.

What to do?

• After the head has begun to set (diameter 5–7 cm), sharply reduce or completely stop nitrogen fertilization.
• Focus on potassium-phosphorus fertilization. Potassium compacts tissues and increases turgor, phosphorus improves root formation and nutrient uptake.
• Use complex fertilizers with low nitrogen content, e.g., monopotassium phosphate (0–52–34) at a rate of 15–20 g per 10 liters of water.

3.4. Potassium Deficiency During the Filling Period

Potassium is the main element responsible for tissue firmness and density. If soil lacks available potassium (especially on light sandy soils), even with normal watering and moderate temperatures, the head remains loose. Symptoms of potassium deficiency: edges of old leaves turn yellow, brown, and dry ("marginal burn"), while young leaves become wrinkled (Welbaum, 2015; Kotov and Adritskaya, 2016).

Why does this happen?

Potassium is involved in the synthesis of cellulose and pectin substances, which form the "framework" of cell walls. It also regulates water balance: when deficient, cells lose their ability to retain moisture, and tissues become flabby. As a result, even tightly packed leaves cannot form a firm head.

What to do?

• Regularly conduct soil analysis and maintain potassium levels within optimal limits (for loams, at least 150–170 mg/kg as K₂O).
• Apply potassium fertilizers 2–3 weeks before head set begins. Potassium sulfate (50 g per 1 m²) or potassium magnesia (40 g per 1 m²) work well.
• On acidic soils (pH below 6.0), potassium uptake is poorer — apply liming to raise pH to 6.5–7.0.

Key Takeaway:

A loose head signals that you are either overheating the plants, watering inconsistently, or have a nutrient imbalance (overfeeding nitrogen or underfeeding potassium). You cannot fix the looseness of an already formed head, but for the next season, you can adjust your growing practices: choose heat-tolerant varieties, monitor soil moisture, and change the fertilization scheme. Remember: a dense head is not only good for market appearance but also a prerequisite for long-term storage.

In the next chapter, we will look at another common problem — head cracking. Why do they burst, when does it happen, and how to prevent yield loss.

4.1. Sudden Watering After Drought

The most common scenario: prolonged heat and no rain, followed by heavy watering or a downpour. Within 1–2 days, the head can split vertically. The inner leaves grow faster than the outer ones, and the pressure splits the head (Dixon, 2007; Nonnecke, 1989).

Why does this happen?

During drought, the plant slows growth, tissues become dense but less elastic. When water is suddenly available, cells swell rapidly, and internal pressure in the head increases sharply. The outer leaves can no longer stretch, and the head bursts from within. Early varieties with thin structures are particularly sensitive.

What to do?

• Water cabbage regularly, avoiding long breaks. Even in dry weather, maintain soil moisture at 70–80% of full water-holding capacity.
• If a watering break was unavoidable, do not give a lot of water at once. Split the watering into several applications — e.g., 10–15 l/m² per day over 3–4 days.
• Mulch the soil to reduce evaporation and smooth out moisture fluctuations.

4.2. Rains After a Dry Period

The same problem, but the cause is not manual watering but the weather. If a heavy rain follows a prolonged drought, cabbage can crack even without your intervention (Welbaum, 2015).

What to do?

• If rain is forecast after a drought, you can lightly cut the roots with a spade on one side of the plant 5–7 days before harvest. This reduces water uptake, making heads less prone to cracking.
• Choose varieties resistant to cracking. Modern hybrids often have a "does not crack" label (e.g., F1 Amager, F1 Sputnik).
• Harvest on time, avoiding over-maturity (see next point).

4.3. Overgrowth and "Aging" of the Head

Even with even watering, heads will eventually start to crack if not harvested. This is a natural process for plants that have reached full maturity: the inner stalk begins to elongate, and the head gradually opens (Kotov and Adritskaya, 2016; Autko et al., 2012).

Why does this happen?

Cabbage is a biennial plant. After head formation, it accumulates reserves, and if not cut, the plant moves to the next phase — stem elongation (bolting). This process starts with the growth of the inner stalk, which pushes the leaves apart, causing the head to split.

What to do?

• Harvest cabbage at technical maturity, when the head is firm but has not yet begun to crack. For early varieties, this is 50–60 days after transplanting; for late varieties, 120–150 days.
• Rely not only on the calendar but also on the head's condition: if the top begins to "open" slightly, it is time to harvest.
• Store late varieties under low temperatures (0–2 °C) — this slows aging processes.

4.4. Excess Nitrogen at the Final Stage

If you continue to actively feed cabbage with nitrogen even after head set, it accelerates inner leaf growth and can trigger cracking, especially combined with excess moisture (Nonnecke, 1989; Wien and Stützel, 2020).

Why does this happen?

Excess nitrogen enhances cell division but does not strengthen cell walls. Inner leaves grow faster than outer ones, and the head bursts from within, like an overinflated balloon.

What to do?

• After head formation begins, eliminate nitrogen fertilization.
• Focus on potassium and phosphorus — they strengthen tissues and increase resistance to cracking (see Chapter 3).

Key Takeaway:

Cracking is a consequence of sharp moisture fluctuations and overgrowth. Main measures: regular watering without "swings," choosing the right variety, timely harvest, and balanced fertilization. If a head has already cracked, it should be harvested and used for processing as soon as possible, because storing such heads is impossible.

In the next chapter, we will discuss internal leaf necrosis — when brown spots and rot appear inside the head, although it looks healthy on the outside.

5.1. Calcium Deficiency in Young Tissues

Internal necrosis occurs when young, actively growing inner leaves lack calcium. Calcium is a largely immobile element in the plant: it enters via the transpiration stream and mostly remains in old tissues, while young leaves receive it poorly. If uptake is disrupted, cells cannot strengthen their walls, they die, and brown necrotic spots form (Nonnecke, 1989; Wien and Stützel, 2020).

Why does this happen?

• Lack of calcium in the soil (often on acidic, sandy, or depleted soils).
• Imbalance with potassium and magnesium: excess of these elements competes with calcium for root uptake.
• Stress impairing root function (waterlogging, drought, high temperature).

5.2. Water Stress and Transpiration Disruption

Calcium enters the plant only with water. If the soil dries out, roots cannot take up calcium. However, with excessive moisture (waterlogging), roots suffocate and also stop functioning. In heat, when evaporation from leaves is strong, calcium is quickly retained in the outer leaves, while inner, poorly ventilated ones do not receive enough (Dixon, 2007; Welbaum, 2015).

What to do?

• Maintain uniform soil moisture at 70–80% of full water-holding capacity (watering 1–2 times a week).
• Avoid water stagnation: plant cabbage on ridges or beds, especially in rainy regions.
• In hot weather, use shading or spray the leaves in the morning and evening to reduce evaporation and improve calcium supply to inner layers.

5.3. Rapid Growth and Nitrogen "Overfeeding"

When cabbage grows too fast (abundant nitrogen fertilization, warm weather), the demand for calcium increases sharply. Calcium fails to reach the rapidly growing inner leaves, and they become necrotic (Kotov and Adritskaya, 2016; Autko et al., 2012).

Why does this happen?

Nitrogen stimulates cell division but does not promote their strengthening. Young tissues expand faster than calcium arrives, making them vulnerable.

What to do?

• Reduce nitrogen fertilization after head set begins (see Chapter 3).
• Apply calcium-containing fertilizers in advance. In autumn or spring during soil preparation — dolomite flour (liming) or chalk (500–700 g per 1 m²), and during the growing season — foliar applications of calcium nitrate (15–20 g per 10 liters of water) 1–2 times at 10–14 day intervals.

5.4. Varietal Predisposition

Some varieties and hybrids are more prone to necrosis, especially fast-growing early and large-headed varieties with thin leaves. Conversely, varieties resistant to cracking and long-term storage (e.g., Amager, Snezhinskaya, and modern F1 hybrids) are less susceptible (Nonnecke, 1989; Wien and Stützel, 2020).

What to do?

• Prefer necrosis-resistant varieties and hybrids.
• If you have had problems before, sow several varieties to reduce risks.

Key Takeaway:

Internal necrosis is not a disease but a result of calcium deficiency in actively growing tissues. Key measures: maintain even moisture, do not overfeed nitrogen, lime acidic soils, and apply calcium fertilizers. Affected heads can be used for processing (after removing necrotic areas), but they are unsuitable for storage.

In the next chapter, we will discuss why a cabbage's growing point may die — when the head does not form at all due to the death of the terminal bud.

6.1. Boron Deficiency

Boron is a critical micronutrient for growing point growth and cell division in meristems. When deficient, young tissue dies, and the growing point perishes. This is a typical physiological disorder intensified in dry weather on light soils with low organic matter content (Nonnecke, 1989; Kotov and Adritskaya, 2016).

What does it look like?

• The terminal bud turns brown and dies.
• Young leaves become brittle, twisted, or deformed; sometimes they thicken and become glassy.
• Instead of one head, several small heads begin to develop from axillary buds (this symptom is easily confused with pest damage).
• In later stages, brown cavities and hollows may appear inside the stalk and petioles (hollowness) (Startsev, 2021).

What to do?

• Conduct a soil test for boron. The optimal content of available boron is at least 0.5–0.8 mg/kg of soil.
• Apply boron as borax (Na₂B₄O₇·10H₂O) at a rate of 1–2 g/m² during soil preparation.
• If the growing season has already started, do a foliar application: dissolve 5–10 g of boric acid in 10 liters of water (first dissolving it in a small amount of hot water) and spray the leaves at the 4–6 true leaf stage and at the first signs of the problem.
• On sandy soils, apply boron every 3–4 years, as it is easily leached.

6.2. Frost in Early Growth Stages

Cabbage is cold-hardy, but young plants at the cotyledon and first true leaf stage are very vulnerable. Prolonged exposure to temperatures around 0…+5 °C, and especially short-term frosts of –3…–5 °C during this period, can damage or completely destroy the growing point (Wien and Stützel, 2020; Welbaum, 2015).

What does it look like?

• With mild damage: after cooling, central leaves become whitish or translucent, growth slows, but the plant may eventually recover.
• With severe damage: the growing point turns black, dries up, and the plant stops developing. Often, several weak side shoots form.
• Distinguishing from other causes: damage appears after a specific frost, usually on field edges or in low areas where cold accumulates.

What to do?

• Transplant seedlings at the optimal time, when the threat of return frosts has passed. For most temperate regions — late May to early June.
• If frost is forecast, cover plantings with spunbond or agro-fabric at night. You can also use sprinkling (fine spray) before frost — water releases heat when freezing, protecting the growing point.
• For spring sowing, choose frost-resistant varieties and hybrids, especially if you live in a risky farming area.

6.3. Mechanical Damage

Damage to the central bud can also occur due to careless soil cultivation (cultivating too close to the plant), hail, strong wind, or planting overgrown or "twisted" seedlings (Nonnecke, 1989; Autko et al., 2012).

What does it look like?

• The growing point may be cut off by a hoe or damaged by tools — then it dries up, and the plant produces side shoots.
• With mechanical damage, symptoms appear immediately after the injury and are localized (only plants in the treated area are affected).

What to do?

• Cultivate carefully, leaving a protective zone of at least 8–10 cm from the stem.
• Do not allow seedlings to overgrow: the optimal age for transplanting is 35–45 days with 4–5 true leaves.
• Use transplanters with a gentle grip to avoid damaging the growing point during planting.

6.4. Differential Diagnosis

Growing point death is sometimes confused with pest damage, but there are differences (Startsev, 2021; Dixon, 2007):

Key Takeaway:

Growing point death is a serious disorder that almost always results in the loss of the head. Prevention includes: timely boron fertilization, protection from frost, and careful handling during cultivation. If the problem has already occurred, the plant is unlikely to recover fully, but you can let it produce side shoots and use them as greens or for small heads (in home gardens, such yields are sometimes processed). In commercial production, affected plants are removed.

In the next chapter, we will look at why hollows may appear inside the head — another unpleasant consequence of rapid growth and boron deficiency.

7.1. Boron Deficiency (Main Cause)

Hollows inside the head are a classic symptom of boron deficiency. Boron is involved in cell wall formation, cell division, and carbohydrate transport. When deficient, tissues in the active growth zone (stalk, bases of petioles) become loose, then die, forming dry or wet cavities (Nonnecke, 1989; Autko et al., 2012).

What does it look like?

• Cavities are most often inside the stalk, closer to the base of the head.
• Cavity walls may be brown or dry.
• With severe deficiency, hollows also appear in petioles of inner leaves.
• Sometimes hollows are accompanied by deformation of young leaves — they become wavy and wrinkled (as with boron deficiency — see Chapter 6) (Startsev, 2021).

What to do?

• Conduct a soil test for available boron (normal range — 0.5–1.0 mg/kg for sandy soils, up to 2 mg/kg for loams).
• During bed preparation, apply borax (Na₂B₄O₇·10H₂O) at a rate of 0.5–1 g/m². Do not exceed the rate — excess boron is toxic.
• During the growing season, do foliar application with boric acid 5–10 g per 10 liters of water (dissolve in hot water, then add cold). Spray at the 4–6 leaf stage and again after 10–14 days if the problem has already appeared.

7.2. Rapid Growth Due to Excess Nitrogen

Rapid growth triggered by abundant nitrogen fertilization can also lead to hollows. Especially if, against this background, the soil is poor in boron or calcium. Tissues do not have time to "mature," breaks form between layers, which then fill with air (Welbaum, 2015; Kotov and Adritskaya, 2016).

Why does this happen?

With a high rate of cell division (nitrogen) and weak tissue compaction (lack of boron, calcium), inner layers grow faster than outer ones. Micro-tears occur, which over time turn into cavities.

What to do?

• Do not overfeed cabbage with nitrogen during the head-filling phase (see Chapters 2 and 3).
• Apply nitrogen in split doses and stop using it 3–4 weeks before harvest.
• Balance nutrition: add potassium and phosphorus — they strengthen tissues and reduce the risk of tears.

7.3. Sharp Moisture Fluctuations

As with cracking (Chapter 4), sharp moisture fluctuations can trigger cavity formation. During drought, tissues compact; during sudden watering, they swell. Internal tears occur, which then do not heal (Dixon, 2007).

What to do?

• Water cabbage evenly, avoiding long breaks (see Chapter 4).
• Mulch the soil to maintain stable moisture.

Key Takeaway:

Hollows inside the head result from tissue structure disruption. The main cause is boron deficiency, but excess nitrogen and unstable watering can also contribute. For prevention: maintain optimal soil boron levels (apply borax or boric acid), do not overfeed nitrogen, and monitor watering. Hollows do not disappear after forming, but in the next season you can completely avoid this problem.

In the next chapter, we will look at why cabbage can become bitter and coarse in taste — how to avoid quality loss even with a good yield.

8.1. Drought and Heat

Cabbage accumulates flavor and tenderness only with sufficient moisture and moderate temperatures. If during active growth (especially 3–4 weeks before harvest) it is hot (above 25 °C) and there is no rain, the plant experiences stress. Under such conditions, the synthesis of bitter glycosides (particularly glucosinolates) and coarse fibers (lignin and cellulose) increases, while sugars accumulate less (Nonnecke, 1989; Welbaum, 2015).

How does this manifest?

• Leaves become tough, "leathery," sometimes with a bluish bloom.
• Taste is bitter or sharp, pungent, without the usual sweetness.
• Varieties with thin leaves suffer especially: they coarsen faster.

What to do?

• Provide cabbage with regular watering, avoiding long breaks (rate 25–30 liters per 1 m² per week, more often in heat).
• In hot weather, use shading (netting, spunbond) or plant cabbage in partial shade (e.g., between rows of corn or sunflowers).
• Mulch the soil to retain moisture and protect roots from overheating.

8.2. Aging and Overgrowth

Even with normal watering, cabbage ages over time: cells become coarse, lignin and tannins accumulate, and sugars are partially consumed by respiration. This is especially noticeable in late varieties if not harvested on time (Kotov and Adritskaya, 2016; Autko et al., 2012).

How does this manifest?

• The head becomes less juicy, leaves become tough and fibrous.
• Slight bitterness appears, especially in outer leaves.
• The inner stalk may start to elongate — a signal that the cabbage is transitioning to flowering (even if the head still looks normal externally).

What to do?

• Harvest cabbage at technical maturity, avoiding overgrowth. Signs of readiness: head is firm, does not yield to pressure, upper leaves begin to bend slightly.
• For long-term storage, choose varieties specifically bred for keeping quality — they age more slowly.
• Cut heads in the cool time of day (morning or evening) and immediately place them in the shade or refrigerator — this slows aging and sugar loss.

8.3. Potassium Deficiency and Nitrogen Excess

Potassium is responsible for tissue firmness and tenderness. When deficient, leaves become coarse, lose juiciness, and may taste bitter. Excess nitrogen, on the other hand, stimulates rapid growth, but tissues remain watery and loose, with low sugar content (Nonnecke, 1989; Kotov and Adritskaya, 2016).

What to do?

• Maintain optimal soil potassium levels (at least 150 mg/kg K₂O on loams).
• Apply potassium fertilizers 2–3 weeks before head set (potassium sulfate, potassium magnesia — 30–40 g/m²).
• Do not overfeed cabbage with nitrogen during the filling period (see Chapters 2 and 3).

8.4. Varietal Characteristics and Storage Conditions

Some varieties (especially old, traditional ones) are inherently coarser than modern hybrids. Bitterness can also increase with improper storage: if heads are exposed to light or elevated temperatures, bitter substances accumulate (Welbaum, 2015).

What to do?

• Choose varieties known for their delicate flavor (e.g., modern F1 hybrids labeled "salad" or "sweet").
• Store cabbage in a dark, cool place (0–2 °C, humidity 90–95%). Avoid drying and overheating.
• If bitterness has already appeared, you can soak shredded cabbage in cold salted water for 30–60 minutes — some bitterness will leach out. But it is better to prevent the problem during cultivation.

Key Takeaway:

Bitterness and coarseness result from stress (heat, drought), overgrowth, nutritional imbalance (excess nitrogen, potassium deficiency), or improper storage. Prevention: regular watering, shading in heat, balanced fertilization (especially potassium), timely harvest, and correct storage. If cabbage has become coarse, it is better used for sauerkraut or stewing than for fresh salads.

In the next, concluding chapter, we will discuss freezing and heat stress — how they manifest and what to do if cabbage has suffered from extreme temperatures.

9.1. Freezing: Symptoms and Consequences

Cabbage withstands short-term frosts down to –5…–8 °C (depending on variety and growth stage). However, at lower temperatures or with prolonged cold exposure, tissues are damaged (Nonnecke, 1989; Welbaum, 2015).

What does it look like?

• Mild freezing (down to –3 °C): leaves become watery, translucent, like "glassy." After thawing, they regain turgor, but brown spots may appear.
• Moderate freezing (–3…–5 °C): leaf edges and tips turn brown, become dry and brittle. Inner leaves may remain undamaged if the head is already formed.
• Severe freezing (below –5…–7 °C): the entire rosette becomes watery, then turns brown and dies. The growing point often perishes (see Chapter 6). Heads become unsuitable for storage — they rot quickly upon thawing (Autko et al., 2012; Kotov and Adritskaya, 2016).

Impact on yield:

• Frost-damaged heads cannot be stored long-term — they are quickly infected by gray and white rot (Startsev, 2021).
• If only the upper part of the head is damaged, it can be used soon (fresh or for processing).
• If the growing point has died — no head will form.

What to do when frost threatens?

• Cover plantings with spunbond or agro-fabric (density 30–60 g/m²) at night. A double layer can be used for safety.
• Use sprinkling — a fine water spray before frost. When water freezes, it releases heat, keeping the surface temperature around 0 °C, preventing more severe damage.
• Transplant seedlings at the optimal time so that the head formation period falls when frost is unlikely.

What to do after frost?

• Do not rush to cut off damaged leaves — allow the plant to thaw naturally (slow thawing reduces stress).
• Inspect the growing point: if it is green and firm, the plant will recover.
• Apply potassium-phosphorus fertilizer (e.g., monopotassium phosphate) — this helps strengthen tissues and speed recovery.
• Harvest damaged heads immediately, without waiting for them to start rotting.

9.2. Heat Stress

Heat for cabbage is no less serious a stress than cold. At temperatures above 25…30 °C, growth slows, leaves coarsen, and heads stop filling or become loose (Dixon, 2007; Wien and Stützel, 2020). Unlike frost, heat stress is often not immediately visible but manifests gradually: wilting, yellowing, marginal leaf necrosis.

Symptoms of heat stress:

• Leaves lose turgor, droop even with normal soil moisture.
• Leaf edges turn yellow, brown, and dry ("marginal burn").
• The head stops growing, becomes loose, or does not set at all.
• Aging accelerates: leaves become coarse, bitterness accumulates (see Chapter 8).

What to do?

• Shade plantings from 11 a.m. to 4 p.m. — use shading nets (50–70% shade), spunbond, or plant cabbage between rows of tall crops (corn, sunflower).
• Water more frequently and abundantly — in heat, the watering rate may increase to 30–40 liters per 1 m² per week, split into 2–3 waterings to prevent waterlogging.
• Use mulch (straw, mowed grass, peat) in a 5–7 cm layer — it protects roots from overheating and reduces evaporation.
• Apply potassium fertilizers — potassium increases resistance to heat stress and improves water balance regulation.
• If heat catches cabbage during head set, you can apply anti-stress preparations (e.g., with humates or amino acids) to increase turgor and reduce evaporation.

9.3. Differential Diagnosis: Frost vs. Heat Stress vs. Calcium Deficiency

Symptoms of heat stress and marginal burn due to calcium deficiency look similar externally, but the causes differ (Nonnecke, 1989; Kotov and Adritskaya, 2016):

Key Takeaway:

Freezing and heat stress are serious challenges for cabbage. Mild freezing is not always fatal, but such heads do not store long. Heat reduces yield and quality even if plants survive. Key protective measures are timely frost protection, shading from heat, regular watering, and maintaining potassium nutrition. Remember: healthy plants, well supplied with moisture and potassium, tolerate temperature stresses better.

Conclusion to the Entire Article

We have covered nine key physiological disorders of white cabbage:

1. Head does not form — heat, long day, excess nitrogen, overcrowding, stress.

2. Loose head — overheating, unstable watering, excess nitrogen, potassium deficiency.

3. Cracking — sudden watering after drought, rains, overgrowth.

4. Internal necrosis — calcium deficiency, water stress, rapid growth.

5. Growing point death — boron deficiency, frost, mechanical damage.

6. Hollows inside the head — boron deficiency, excess nitrogen, rapid growth.

7. Bitterness and coarse texture — drought, heat, aging, nutritional imbalance.

8. Temperature stress — freezing and heat stress, their symptoms and recovery.

All these disorders are not transmitted from plant to plant and are mostly preventable. The main strategies for successful cabbage cultivation are:

• Choosing varieties and hybrids resistant to major stresses (heat, cracking, necrosis).
• Observing sowing and planting dates so that critical growth phases coincide with favorable temperature conditions.
• Even watering, maintaining soil moisture at 70–80% of full water-holding capacity.
• Balanced nutrition — without nitrogen bias, with sufficient potassium, calcium, and boron.
• Covering and shading during extreme temperatures.

If a problem has already appeared, you may not always be able to save the crop, but you will definitely be able to draw the right conclusions and avoid it in the next season. Observe your plants, note what went wrong, and adjust your growing practices. Cabbage is a rewarding crop, and with proper care, it will reward you with dense, juicy, and tasty heads.