Preparation of seed tubers

Virus Load: The Invisible Enemy

The greatest danger threatening seed potatoes is viral diseases. Being a vegetatively propagated crop, potatoes accumulate viruses year after year. This phenomenon is known as potato degeneration (Балашев & Земан, 1981). Viruses such as Potato Leafroll Virus (PLRV), Potato Virus Y (PVY), or Potato Virus X (PVX) can remain in tubers for a long time in a latent form, showing no external symptoms. However, they sap the plant's strength from within.

• How does it work? Viruses disrupt metabolism, weaken photosynthesis, and slow down growth. The plant becomes less productive and more vulnerable to other diseases. Even if the bush looks healthy externally, its yield can be reduced by 15-20%, and with a high degree of infection—by 50-70% (Dean, 1993).
• What should a gardener do? The main rule is to use only certified seed material. Certification is a system of checks that guarantees the tubers were grown from healthy microclone plants and have passed field inspections and laboratory tests for viruses. By buying potatoes "for eating" at the market, you risk bringing a whole host of viral infections to your plot (De Jong et al., 2011). If you use your own planting material for several years in a row, it is crucial to conduct a rigorous annual selection: leaving for seed only tubers from the healthiest and most productive bushes to slow down the accumulation of viruses.

Physiological Age: The Energy of Your Potato

A tuber is not just a passive store of starch. It is a living, developing organ that ages. The physiological age of a tuber is its stage of development, which strongly influences how the new plant will grow (Struik, 2007). This age is affected by growing conditions, harvest time, and, most importantly, storage conditions.

• Young tuber (e.g., freshly harvested or properly stored at low temperatures) has strong apical dominance. When sprouting, it will produce one or two powerful sprouts from the eyes at the top. The plant will have few stems (1-2), but they will be large and will form a small number of very large and uniform tubers. Such planting material is ideal for regions with a long growing season, where you can obtain a high yield of large marketable potatoes (Dean, 1993; Welbaum, 2015).
• Old tuber (e.g., stored for a long time at elevated temperatures) loses apical dominance. When sprouting, many thin sprouts appear from all the eyes. The bush will have 4-6 or more stems, which will form many, but small, tubers. Such material gives an earlier harvest, which is important for regions with short summers, but the total yield and marketable size will be smaller (De Jong et al., 2011; Котов & Адрицкая, 2016).

Therefore, when choosing tubers, it is important to know their "history." Old, overgrown tubers may have thread-like and weak sprouts, leading to sparse emergence. Too young tubers that have not gone through a dormancy period will have delayed and uneven emergence.

Sprouting Energy: The Key to Uniform Emergence

Sprouting energy is the ability of all the eyes of a tuber to produce viable sprouts in a short period. This determines how uniformly and vigorously your plot will emerge.

• Signs of good energy: Uniform, strong sprouts appear from most eyes within a short time. Plants develop synchronously, which simplifies care and ensures uniform maturation of the crop.
• What reduces it? Besides viruses and physiological aging, sprouting energy is suppressed by improper storage conditions (sharp temperature fluctuations, lack of oxygen, damage by fungal and bacterial rots), as well as mechanical damage. For example, even in a healthy tuber, if stored with poor ventilation, carbon dioxide can accumulate, inhibiting sprouting (Dean, 1993).

Conclusion from Chapter 1: The success of your potato season is determined by 80% at the moment of choosing the planting material. Do not chase cheapness. Buy tubers from trusted producers, pay attention to the availability of documents on the variety and health. And always remember: a healthy, properly "aged" tuber with high sprouting energy is the starting capital of your future harvest.

Tuber Size: The Golden Mean

The size of the seed tuber is one of the main factors influencing the growth vigour of the future plant. A larger tuber contains more reserve nutrients (starch, proteins), which are necessary for the young plant during the period from planting to the emergence of its own root system and first true leaves (Dean, 1993). This provides an initial advantage: emergence is faster, and the plants are more vigorous and resistant to stress.

• Optimal size: Most agronomists agree that the ideal weight for a seed tuber in the temperate zone and most regions is 50–80 grams (Welbaum, 2015; Котов & Адрицкая, 2016). In terms of diameter, these are tubers about the size of a chicken egg or slightly larger. This size provides a balance: the tuber is large enough to give a vigorous start, but not so large that the seed consumption becomes economically unjustified.
• Small tubers (under 30–40 g): They can be used, but only if they are healthy, high-generation material. However, the yield from them is generally lower, and the plants less vigorous. Small tubers should be planted more densely to compensate for the loss in growth vigour (Балашев & Земан, 1981).
• Large tubers (over 100 g): They produce excellent, vigorous plants and high yields, but their consumption per hundred square metres or hectare is too high. In addition, very large tubers often have hollow hearts or other internal defects. It is more advantageous to cut them into several parts (we will discuss this in one of the following chapters) to obtain more planting material without sacrificing quality.

Shape and Appearance: Signs of Health

Culling based on external signs is your main tool in the fight against diseases. Carefully inspect each tuber. Specimens with any signs of damage are absolutely unsuitable for planting:

• Rots (wet, dry, ring): Soft, watery areas, unpleasant odour, dark depressions on the surface or inside the tuber. These are bacterial and fungal infections.
• Common scab: Hard, corky growths or ulcers on the skin. Although scab does not significantly reduce yield, it worsens the marketable appearance and can become a source of infection in the soil. It is better to discard such tubers.
• Rhizoctonia (black scurf): Small black, hard sclerotia on the skin surface, resembling stuck lumps of soil. This fungal disease can strongly delay emergence and lead to the formation of deformed tubers.
• Mechanical damage: Deep cuts, severe bruises, crushed areas. Pathogens of rot easily penetrate the tuber through such wounds. Small scratches and abrasions, if they have healed (corked over), are not dangerous.
• Ugly shape: Fused, pear-shaped, highly elongated tubers are often a sign of degeneration, viral infection, or unfavourable growing conditions from the previous year (Балашев & Земан, 1981). They produce weak, low-yielding progeny.

Important rule: The skin of the seed tuber should be firm, without cracks, and with a colour characteristic of the variety. When in doubt, discard.

Varietal Purity: The Guarantee of Predictability

If you are growing potatoes not for experimentation but for a stable yield, varietal purity is a crucial characteristic. Planting tubers in which different varieties are mixed leads to discrepancies in emergence time, flowering, maturation, as well as significant losses during storage.

• How to check? The simplest method is to carefully sort the tubers before planting and remove any that differ sharply in skin colour, eye shape, or sprout growth. Also, pay attention to "bouquet" bushes during the growing season—if several bushes of different habits have grown from one tuber, this is a clear sign of varietal admixture, and such plants should be removed (De Jong et al., 2011).

What If There Are Few Tubers or They Are Small?

There is a solution! If you only have small but healthy tubers, or if you want to save large material by cutting them, you can plant them more densely than recommended for standard tubers. The smaller the size of the seed tuber, the closer together they should be planted in the row to ensure the required stem density per unit area (Котов & Адрицкая, 2016). Keep in mind that smaller tubers will produce smaller daughter tubers, so such planting is better used if your goal is to obtain planting material for the next season or small early potatoes.

Conclusion from Chapter 2: The right choice of tuber is not just sizing. It is a systematic approach that includes assessing health, shape, and varietal purity. Approach this stage with full responsibility, and your plants will reward you with uniform emergence and a high yield.

What Is Sprouting and Why Is It Needed?

Sprouting (often referred to in agronomic literature as pre-planting vernalisation or light sprouting) is the process of artificially awakening the eyes on tubers under controlled conditions, before planting them in the ground (Балашев & Земан, 1981). This technique mimics the onset of spring and gives the tuber the command to "wake up" and prepare for growth.

Main tasks of sprouting:

1. Accelerating emergence: A sprouted tuber spends less time awakening in cold soil. This provides a head start of 7–14 days compared to unsprouted material. For regions with short summers, this difference is critical (De Jong et al., 2011; Котов & Адрицкая, 2016).

2. Evening out emergence: Instead of emerging unevenly over 2–3 weeks, plants from sprouted tubers appear almost simultaneously. This simplifies care (watering, fertilising, Colorado potato beetle treatments) and allows all plants to develop synchronously, which positively affects the overall yield.

3. Increasing early yield: Plants that started photosynthesising a week earlier have time to form larger foliage, and consequently tubers, by the time hot or dry weather arrives. Research shows that sprouting can increase early potato yield by 15–30% (Welbaum, 2015; Ториков & Сычев, 2018).

4. Reducing the risk of infection: The short, sturdy sprouts that develop from light sprouting are less susceptible to mechanical damage during planting and emerge through the soil layer faster. This reduces the risk of rhizoctonia and other soil-borne diseases at the emergence stage.

Why Sprouting Works: A Scientific Perspective

In tubers stored in the dark, inhibitory substances accumulate that maintain the state of dormancy. Light destroys these inhibitors. Furthermore, illumination stimulates the synthesis of chlorophyll and phytochrome—substances that control growth processes (Dean, 1993). As a result:

• Sprouts become short, thick, and green. They do not overgrow, do not break off during planting, and do not drain unnecessary energy from the tuber.
• Enzymes are activated, converting starch into soluble sugars. These sugars serve as an easily accessible energy source for the young roots and sprouts in the first days after planting, before the plant's own root system has formed.

This is fundamentally different from dark sprouting, which occurs in storage facilities or vegetable pits. There, sprouts become long, fragile, and white (etiolated). Such sprouts are a sign that the tuber is "aging" (so-called forced sprouting) and is losing its planting qualities. When planted, they break off easily, which can lead to the death of eyes and sparse emergence (Балашев & Земан, 1981).

The Light Sprouting Method: Step-by-Step Instructions

This is the most common and reliable method for the garden.

1. Preparation: Approximately 30–40 days before the planned planting, take the tubers out of the storage where they lay in the dark. Carefully sort through them, discarding diseased, frostbitten, or rotting ones. Soak or spray the tubers with a weak solution of copper sulfate or potassium permanganate for additional disinfection (optional).

2. Conditions: Lay the tubers in one or two layers in boxes or on shelves in a bright, well-ventilated room. It is important that the tubers receive diffused sunlight or artificial lighting. Direct sunlight can cause burns and excessive heating.

3. Temperature: The optimal temperature for sprouting is 12–16 °C (De Jong et al., 2011; Welbaum, 2015). At higher temperatures, sprouts elongate and become fragile. At lower temperatures, the process is delayed.

4. Turning: Every 7–10 days, carefully turn the boxes or rearrange the tubers so that light and air reach all sides, and the sprouts develop evenly.

Alternative Sprouting Methods

For those who do not have a bright room, there are other approaches, but they are less effective or have their own nuances.

• Sprouting in a moist environment: Tubers are laid in layers, interspersed with moist sawdust, peat, or humus. In this case, sprouts are white and have numerous roots. This method gives very rapid development, but such sprouts are very fragile. A delay in planting of even 2–3 days leads to their overgrowth and brittleness, which can sharply reduce the quality of the planting material (Балашев & Земан, 1981).
• Warming: A simple and quick method for those who are late. 2–3 days before planting, the tubers are placed in a warm place with a temperature of 18–22 °C. This does not produce full sprouts, but awakens the eyes and accelerates emergence after planting, though not as strongly as full light sprouting.

The Main Rule: Do Not Over-Sprout

The most common mistake in sprouting is keeping the tubers too long. The optimal sprout length by planting time is 0.5–1 cm (De Jong et al., 2011). Such "bud-sprouts" are already ready for growth, but will not break off during planting. If sprouts become longer than 2–3 cm, they are almost guaranteed to break off when planted, and the tuber will have to re-sprout, losing time and energy.

When Is Sprouting Not Needed or Even Harmful?

• For very old, "over-stored" seed material: Such tubers have already produced numerous thin sprouts (physiological aging). Sprouting will worsen the situation, and you will get many weak bushes with small tubers. Such potatoes are better planted without preparation or used only for early forcing of greens.
• If you are planting very large tubers cut into parts: Fresh cuts should not be exposed to light for long. They are better sprouted in a moist environment or using stimulants, but light sprouting of cut potatoes should be avoided, as they quickly lose moisture and become vulnerable to infections.
• When planting in dry, overheated soil: If the soil is dry and warm, long sprouts may simply dry out. In this case, it is better to carry out moist sprouting or warming, and then immediately plant in a well-watered furrow.

Conclusion from Chapter 3: Sprouting is not a whim, but a scientifically based method that allows you to increase the early yield, even out emergence, and protect plants from stress. The main thing is to do it correctly: provide light, maintain the temperature regime, and stop in time so that the sprouts do not overgrow.

Choosing a Location and Preparing the Tubers

Sprouting should take place in a bright, well-ventilated room. This could be:

• A heated greenhouse or veranda. An ideal option, as there is enough natural light.
• A bright room in a house or barn with windows. If light is insufficient, use additional lighting (fluorescent or grow lights) at approximately 50–70 W per 1 m² of the area where the tubers are laid out (Балашев & Земан, 1981).
• Boxes or shelves. Tubers are laid out in one or two layers so that they do not touch each other. This ensures air circulation and even lighting. You can use boxes with a slatted bottom for better ventilation.

Preparation of tubers before sprouting:

1. Culling. Sort the tubers again, removing any suspicious ones: with signs of rot, mould, spots, mechanical damage, or too thin thread-like sprouts (a sign of severe degeneration).

2. Disinfection (optional). To prevent fungal diseases, tubers can be sprayed or briefly soaked in a weak solution of potassium permanganate (0.01–0.05%) or a 1% solution of boric acid. Afterwards, they need to be dried.

3. Warming (quick start). If you are late starting the sprouting, you can place the tubers in a warm place (18–20 °C) for 2–3 days 7–10 days before planting to "wake up" the eyes, and then begin light sprouting.

Sprouting Conditions: The Three Pillars of Success

To obtain strong, high-quality sprouts, three main conditions must be met:

1. Temperature – The Golden Mean (12–16 °C). This is the most important parameter. At this temperature, sprouts develop slowly but become thick, short, and dark green, with root primordia (De Jong et al., 2011). They will be resistant to mechanical damage during planting.

• Too warm (>20 °C): Sprouts elongate, become long and fragile, losing their value.
• Too cold (<8–10 °C): Sprouting is significantly delayed (up to 50–60 days), sprouts may acquire a purple hue (a sign of stress), although for some varieties this is acceptable (Welbaum, 2015).
• Light – The Main Stimulant. It is diffused light that turns ordinary sprouts into short, thick, and green ones. Light slows down the stem elongation and stimulates thickening, and also initiates chlorophyll synthesis. If there is insufficient light, the sprouts will be pale and elongated.
• Direct sunlight is dangerous—it can overheat the tubers and cause burns (brown spots). Use shading (gauze, white fabric) or artificial lighting.
• Optimal day length is 10–12 hours per day. On cloudy days, supplement with lamps.
• Air Humidity – Do Not Allow Drying Out. During sprouting, tubers lose moisture, but excessive dry air (below 60–70%) leads to their shrivelling and reduced quality. To maintain humidity, you can periodically (every 2–3 days) lightly spray the air around the boxes or place containers with water. The humidity of the substrate (if sprouting in a moist environment) should be moderate—without water stagnation.

Sprouting Timing: When to Start?

The timing depends on how early you want to get the harvest.

• For ultra-early production (second half of June): Start sprouting 40–50 days before planting. This will allow you to get the largest and most vigorous sprouts.
• For early production (July): 30–40 days is sufficient.
• For the main harvest (August–September): You can limit yourself to 20–25 days, just to even out emergence and slightly accelerate development.

Guideline: if you plant potatoes in late April – early May, then start sprouting in mid-March (Балашев & Земан, 1981; Котов & Адрицкая, 2016). It is important to remember that too long sprouting (more than 50 days) can lead to overgrowth and aging of sprouts, so keep to the schedule.

Controlling Sprout Length: The Main Thing Is Not to Overgrow!

The most frequent question: “How long should the sprouts be by planting time?”. The answer is unequivocal: 0.5–1.5 cm. These are the so-called "bud-sprouts" (De Jong et al., 2011; Ториков & Сычев, 2018). They are already alive, ready to grow, but compact and do not break off when planted.

• If sprouts become longer than 2–3 cm, they become brittle. When planted, they are almost guaranteed to break off, and the tuber will have to form a new sprout, delaying emergence by 1–2 weeks.
• If the sprouts have overgrown, you can try to preserve them by shading the tubers (removing light) 5–7 days before planting. This will cause the formation of root primordia on the sprouts, which will slightly reduce brittleness.

Control technique: 3–5 days before planting, tubers with sprouts can be lightly covered with moist sawdust or peat. This will stimulate the formation of a root system on the sprouts, accelerating establishment after planting.

Alternative: Sprouting in a Moist Environment

For those who do not have a bright room, there is a method of sprouting in a moist substrate (sawdust, peat, humus). The tubers are laid in layers, interlaid with moistened material, at a temperature of 12–15 °C.

• Pros: very rapid (10–15 days) formation of sprouts and a powerful root system.
• Cons: the sprouts are long, white (etiolated) and very fragile. They break off easily when planted, making this method risky (Балашев & Земан, 1981).

Advice: this method can only be used with very careful planting (by hand, without mechanical damage) and when you are sure you can plant the tubers immediately as soon as the sprouts appear.

What to Do If Tubers Start Sprouting Too Early?

Sometimes tubers start sprouting in storage before the scheduled time. This happens at elevated temperatures and humidity.

• Do not despair! If the sprouts are long and white, they can be broken off (removal) when they reach 5–8 cm in length. After this, the tuber will form new, stronger sprouts, though the process will take additional time (Ториков & Сычев, 2018).
• If the sprouts are already green and long, they can also be carefully removed, but it is better to use such potatoes for planting at the earliest possible date so they do not lose energy.

Conclusion from Chapter 4: Proper sprouting is a balance of temperature, light, and time. Follow these three conditions, control the length of the sprouts, and do not allow them to overgrow. Then your planting material will be as effective as possible, and the harvest will be early and abundant.

When Is Cutting Justified?

1. Large tubers (over 80–100 g): This is the most common and reasonable case. One large tuber can be cut into 2–3 parts, obtaining more planting units. At the same time, each part will be large enough (40–60 g) to give the plant a vigorous start (Dean, 1993). The savings in material are obvious.

2. Little planting material: If you have only a few valuable tubers of a rare variety, cutting allows you to increase their number and get more plants.

3. Stimulation of tillering (formation of more stems): In a whole tuber, usually only 1–2 apical eyes germinate (apical dominance). By cutting the tuber, you remove this dominance and "awaken" the lateral eyes. As a result, each part grows a plant with 2–3 stems, which increases the total number of stems per unit area and, consequently, the number of tubers per nest (Welbaum, 2015; Котов & Адрицкая, 2016). However, remember that there will be more stems, but the tubers themselves will be smaller—this technique is more suitable for obtaining seed material or potatoes for early consumption.

When Is Cutting Absolutely Not Allowed?

1. Small and medium tubers (under 50 g): Cutting will not save anything, and each part will be too small (under 25–30 g). Such small pieces contain few nutrients, the sprouts will be weak, leading to sparse emergence and reduced yield (Балашев & Земан, 1981).

2. Tubers with signs of disease: Cutting a diseased tuber is a way to spread the infection to healthy parts. Fungi and bacteria from the knife will get on the cut, and even if you do not notice symptoms, the infection will penetrate deep and manifest after planting.

3. When planting in cold, waterlogged, or very dry soil: In cold and wet soil, the cut is an open wound that rots faster than it can heal. In dry soil, the tuber, deprived of protective skin, loses moisture, shrivels, and may not emerge. Cut potatoes are planted only in soil warmed to 8–10 °C and moderately moist (De Jong et al., 2011).

4. Too old, "over-stored" tuber: In such tubers, the eyes are already depleted, and cutting will only weaken them, without producing the desired effect.

How to Cut Correctly: Step-by-Step Instructions

If you decide to cut the tubers, do it wisely to minimise risks.

1. Warm the tubers: Before cutting, the tubers should be warm (15–20 °C). Cold tubers are more brittle and break, and cuts heal less well. Take them out of storage 7–10 days before cutting (Dean, 1993).

2. Use a sharp and clean knife: The knife must be sharp to make a clean cut, not a jagged one. A jagged cut takes longer to heal. Between tubers, and especially between different varieties, the knife must be disinfected. Dip the blade in a solution of potassium permanganate, medical alcohol, bleach (e.g., a 1% solution), or simply a dark solution of potassium permanganate (Балашев & Земан, 1981). This prevents the transmission of infection from a diseased tuber to a healthy one.

3. How to cut: Cut lengthwise from the top (where there are more eyes) to the base (the heel end). Try to ensure that each part has 2–3 healthy eyes. The optimal weight for a piece is 40–60 g (De Jong et al., 2011). The upper part of the tuber contains more nutrients and produces more vigorous sprouts, so try to cut pieces of roughly equal volume.

4. Plant immediately or dry: This is the most important point!

• Best option: Plant the cut tubers immediately, without letting the cut dry out. A wet cut heals (suberinises) faster in the soil, and the risk of infection is reduced (De Jong et al., 2011). This is especially relevant in warm and humid weather.
• If planting is delayed: Place the cut pieces in boxes in one layer and leave them for 3–4 days in a warm (15–20 °C), well-ventilated place. A protective cork tissue (suberin) will form on the cut—this is a natural "plaster" that prevents moisture evaporation and protects against infections (Welbaum, 2015). To accelerate suberinisation, the cuts can be dusted with ash or crushed charcoal.
• Treatment of cuts: For additional protection against rots and stimulation of growth, the cuts can be treated with special preparations: powdered fungicides (e.g., based on TMTD) or growth stimulants (e.g., heteroauxin). In small farms, dusting fresh cuts with wood ash or a mixture of ash and fungicide has proven effective (Котов & Адрицкая, 2016). This disinfects and dries the wound.

Alternative to Cutting: Stimulating Incision

This method allows you to avoid completely dividing the tuber, but achieves an effect similar to cutting—awakening more eyes.

• How it is done: 2–3 weeks before planting, a shallow (0.5–1 cm) transverse incision is made in the middle part of the tuber, without cutting it into two pieces. This disrupts the integrity of the vascular vessels, and nutrients stop flowing only to the apical eyes. As a result, the lateral buds begin to awaken, but the tuber remains whole, reducing the risk of rotting (Балашев & Земан, 1981).

Myths About Cutting

• “Cut potatoes give a smaller yield”: This is not entirely true. If cut correctly (from large tubers, following all rules), the yield per unit area is not inferior to that from whole tubers. There will simply be more tubers per nest, and their size slightly smaller.
• “Cut potatoes cannot be stored”: This is true. Cut potatoes are not intended for long-term storage. They should be used within 1–2 weeks. If you have cut a lot and cannot plant them in time, use the drying method and store them in a cool but not cold place (about 5–8 °C) to inhibit growth but prevent rotting.

Conclusion from Chapter 5: Cutting tubers is an effective and justified technique if you use large, healthy material, maintain cleanliness, and plant in favourable conditions. The main rule: cut only immediately before planting or create conditions for rapid healing of the cut. Be cautious with diseased, small, and over-stored tubers—it is better not to cut them.

Why Is Treatment Needed?

Imagine the tuber as a spaceship with a crew of sprouts. It is about to land on an unknown planet (the soil), where dangers lurk: pathogenic fungi (causing rhizoctonia, fusarium, late blight), bacteria (causing wet rot, blackleg), and soil-dwelling pests (wireworms, mole crickets). The task of pre-planting treatment is to create a protective barrier and provide the crew with everything necessary for a successful mission (Dean, 1993; Ториков & Сычев, 2018).

Treating tubers solves three main tasks:

1. Disinfection (dressing): Destroying pathogens that are on the surface and in the upper layers of the skin.

2. Growth stimulation: Activating enzymes, accelerating germination, developing a powerful root system.

3. Nutrition: Providing trace elements necessary for the initial stages of development, until the plant can extract them from the soil on its own.

Treatment Options: From Folk Remedies to Modern Preparations

There are many treatment methods—from simple and affordable to professional. The choice depends on your goals, the availability of preparations, and your preferences.

Treatment Scheme: How to Do It Correctly?

The ideal scheme depends on the condition of your material and your goals. Here are a few options:

1. Basic protection: Spraying tubers with a solution of potassium permanganate + dusting with wood ash. This option is the simplest, most accessible, and safest for beginners.

2. Enhanced protection: Soaking in a biofungicide solution (“Fitosporin”) for 1–2 hours before planting. This will provide good protection against fungal and bacterial infections.

3. Maximum preparation (for early harvest): 2–3 days before planting, spray the tubers with a solution of complex micronutrient fertiliser with the addition of a growth stimulant (“Zircon” or “Epin”). Then, immediately before planting—dust with wood ash.

4. Professional approach (for large volumes): Use specialised dressings (“Prestige”, “Maxim”). Treatment is carried out mechanically, but for the garden, a knapsack sprayer can be used.

5. Treatment of cut tubers: Cuts are especially vulnerable. They must be treated! The most reliable method is dusting fresh cuts with a mixture of fungicide (e.g., “TMTD” or “Maxim”) with wood ash (1:1). This simultaneously disinfects, dries, and stimulates healing (Балашев & Земан, 1981).

Main rule: All treatments are best carried out immediately before planting or 1–2 days before. This minimises the risk of re-infection. Do not use too many different preparations at once—this can cause chemical burns or neutralise each other's effects. Alternate: first the dressing, the next day the stimulant, and before planting—ash.

Conclusion from Chapter 6: Pre-planting treatment of tubers is an effective way to protect the future harvest from diseases and give a powerful start for growth. Choose preparations according to your tasks and capabilities, follow dosages, and do not forget about safety. A well-prepared tuber means a healthy plant and a bountiful harvest.

Signs of Readiness: What Should Sprouts Look Like?

The main and most obvious criterion is the condition of the sprouts. Ideally, by planting time, they should meet the following characteristics (De Jong et al., 2011; Котов & Адрицкая, 2016):

1. Sprout length – 0.5–1.5 cm. This is the most important characteristic. Such a sprout has not yet overgrown; it is strong, firm, and will not break off when planted. Long sprouts (more than 2–3 cm) become brittle, and when covered with soil, they are almost guaranteed to break off. In this case, the tuber will have to form new sprouts, delaying emergence by 1–2 weeks.

2. Sprout colour – dark green or purple. This is the result of light sprouting. Such sprouts actively photosynthesise and are resistant to damage. Pale or white sprouts indicate a lack of light or that the tubers sprouted in the dark. They are more fragile and weaker.

3. Presence of root primordia. In well-prepared tubers, small bumps—primordia of future roots—appear at the base of the sprouts. This is an excellent sign: after planting, they will quickly start growing, and the plant will begin feeding from the soil earlier.

4. Sprouts are evenly distributed—this indicates that you turned the boxes during sprouting and all the eyes received enough light.

Important nuance: Different varieties have different sprouting energy. Some varieties (e.g., early ones) produce shorter and thicker sprouts even with prolonged sprouting. Others (late varieties) may produce long and thin ones. Judge by the overall condition: if the sprouts are short and green—everything is fine.

Readiness of the Planting Material as a Whole

Besides the sprouts, pay attention to the overall condition of the tubers:

• Tubers should be firm. If they have become soft, shrivelled—this is a sign of moisture loss. Such tubers will give weak emergence. Sprouting in a dry room could have led to their dehydration. In this case, they can be soaked in room-temperature water for a few hours before planting.
• Cuts (if you cut the tubers) should have healed. A dense cork tissue (suberin) should have formed on the cut. If the cut is wet, slimy, or darkened, the tuber is infected, and it is better to discard it.
• No signs of disease. During sprouting, any hidden diseases should have manifested: mould, rot, spots have appeared. Remove such tubers immediately to prevent them from infecting others during planting.

External Conditions: When Is the Soil Ready to Receive the Tubers?

Even ideally prepared tubers will not give a good harvest if planted at the wrong time. The gardener needs to wait for the right weather conditions. Here, the main criteria are soil temperature and its moisture (Dean, 1993; Welbaum, 2015).

1. Soil temperature: The optimal temperature for planting potatoes is 8–10 °C at the planting depth (about 10 cm). This is a critical threshold. At lower temperatures, the tubers lie in the ground without moving, “waiting” for warmth, while they may be affected by rot pathogens. At higher temperatures (above 12–15 °C), tubers germinate quickly, but the sprouts may be weakened if the soil is dry.

• How to measure? A simple method is to bury an ordinary outdoor thermometer in the soil at a depth of 10 cm for 15–20 minutes. Or use more accurate soil thermometers. Relying on the average daily air temperature is unreliable because the soil warms up more slowly. A folk sign: when buds begin to open on birch trees, the soil at a depth of 10 cm warms to 7–8 °C. But it is still better to check with a thermometer.
• Soil moisture: The soil should be moderately moist. It should not be wet like a swamp, nor crumble to dust.
• Check: Take a handful of soil from a depth of 10–15 cm and squeeze it in your palm. If water oozes from the clump—too wet, wait. If the clump crumbles to dust—too dry, watering is needed. If the clump holds its shape but crumbles easily when pressed—ideal. In such soil, there is good air exchange, and the tubers do not rot.

Planting: What to Do If Sprouting Has Been Delayed?

Sometimes you have prepared the tubers, but the weather does not allow planting (cold, wet). The sprouts have already overgrown. What to do?

1. Slow down growth: 5–7 days before planting, move the tubers to a cooler place (8–10 °C) and slightly shade them. This will slow down sprout growth and allow them to strengthen.

2. Careful planting: When planting, be especially careful. Place the tubers in the furrow with sprouts facing up and do not press them hard when covering with soil. You can plant the tubers slightly deeper (by 2–3 cm) to protect long sprouts from drying out.

3. Hilling after emergence: If the sprouts do break off—it is not a disaster. Potatoes have a high regenerative ability. If the central sprout is damaged, lateral buds are awakened. However, emergence will be later. To support such plants, after emergence, apply nitrogen fertiliser (urea) and loosen the soil to stimulate the growth of replacement shoots.

When to Plant: Calendar Guidelines

Although the main guide is soil temperature, some calendar recommendations can be given depending on the region:

• Southern regions (Krasnodar Krai, Crimea, Rostov Oblast): Planting is possible from late March – early April. The soil warms up quickly.
• Central Russia (Moscow region, temperate zone): Optimal dates are from April 20 to early May. Aim for the “May holidays” as the classic time.
• Northern regions, Ural, Siberia: Planting is shifted to the second half of May, when the soil has finally thawed and warmed to 8–10 °C.

Main rule: It is better to plant a week later, in warm and moderately moist soil, than a week earlier, in cold and wet soil. Too early planting in cold soil is the main cause of tuber rotting and sparse emergence.

Conclusion from Chapter 7: The readiness of tubers for planting is determined by three factors: the condition of the sprouts (strong, green, 0.5–1.5 cm long), the condition of the soil (warmed to 8–10 °C, moderately moist), and the absence of signs of disease. Adhering to these three conditions guarantees fast, uniform, and vigorous emergence, which will be the key to an abundant harvest.