Potatoes are one of the most commonly-grown crops, as they produce high yields if planted under favorable conditions. However, nothing is as disappointing as finding out your healthy-looking plant didn’t produce any potatoes after a long, tiresome growth season. Therefore, if you’re wondering what the reason for this unfortunate turn of events might be and how to prevent it from happening going forward, this article is for you.
Reasons why your potato plant didn’t produce potatoes might include high temperatures, high nitrogen fertility in the soil, moisture stress, the use of diseased seed potatoes, and rushed harvesting.
In the following sections, I’ll discuss why a potato plant may fail to produce potatoes (the tubers). I’ll also explore a few topics related to the question in great detail. So, let’s get started!
Possible Reasons For Poor Yields in Your Potato Plants
Poor yields in your potatoes can happen due to high temperatures and moisture stress during the growth season. But, that’s not all. Your potato plants might not have produced tubers if you applied fertilizers inappropriately, used diseased potato seeds, or rushed to harvest.
Now, let’s have a detailed look at each of these possible causes of poor potato yields:
High Temperatures
Potatoes (Solanum tuberosum L.) are cool-season plants with specific temperature needs. The best time to plant your potato seeds is in early spring, around 1 to 2 weeks before the last frost date.
It is also advisable to plant your seeds as soon as the soil is workable, even when the date doesn’t coincide with the start of the proposed planting season if you want to harden your potato plants.
Proper timing and favorable temperatures are vital in preventing poor yields in potatoes.
You might end up with low (or no yields) if you plant your potato seeds at the wrong time. Generally speaking, potato plants develop optimally at 20 °C (68 °F). However, the plants have varying temperature requirements at different growth stages as follows:
- The haulm (stem and leaves) grows faster at a temperature range of 20 – 25 °C (68 – 77 °F).
- The tubers develop best at 15 – 20 °C (59 – 68 °F).
For maximum yields, a potato plant should have a good balance of the diurnal temperature cycle – warm days and cool nights. However, if you plant your potatoes when the days are too hot, there’ll be a delay in tuber formation and an unnaturally increased growth. Consequently, this delay could lead to poor yields if you don’t extend your potatoes’ growing season.
Studies show that potatoes’ tuberization (formation and growth of tubers) is best achieved at lower temperatures.
Increased temperatures cause heat stress, which adversely affects various physiological, morpho-anatomic, and biochemical processes in a plant. Therefore, if your potato plant experiences high temperatures when it’s about to form tubers, this will significantly influence the tuber formation.
Here are two ways that heat stress affects tuberization in potatoes:
Distribution of Carbohydrates
Plants manufacture carbohydrates during photosynthesis, and the optimal temperature for this process is 23 °C (75 °F). However, when the temperatures go beyond 30 °C (86 °F), the plant experiences heat stress. As a result, the plant will prefer to distribute its carbs to the haulm instead of the root region.
In some cases, if the plant has already started forming tubers, it will reabsorb some carbohydrates from them to nourish the stem and leaves. As you can imagine, this will lead to reduced tubers, and they may vanish if the heat stress continues.
The distribution of carbohydrates in a plant is the function of various plant hormones that regulate a plant’s physiological and metabolic activities.
Apart from distributing carbohydrates, plant hormones control the growth of different plant parts.
For instance, gibberellic acid, auxins, and abscisic acid are involved in tubers, leaves, and stolon formation. Moreover, environmental conditions such as temperature variations affect the working mechanisms of these hormones.
Gibberellic acid stimulates the growth of leaves and the stolon. Therefore, this hormone’s concentration will need to decrease within the potato plant for the tubers to form. Contrastingly, auxins and abscisic acid promote tuberization, and their levels shoot when the plant is ready to form tubers.
High temperatures cause an increase in gibberellic acid production, which in turn leads to a decreased production of auxins and abscisic acid. Therefore, this fluctuation of hormones promotes leaf and stolon growth and hinders the formation of potato tubers.
Tuber Disorders
Heat stress is also one of the main causes of tuber disorders in potatoes. For instance, “sugar (jelly) end” or “translucent end” is a tube disorder that occurs when reducing sugars accumulate at the stem end of the tubers, from where they get distributed to the leaves.
The scenario promotes canopy formation at the expense of tuberization since the plant extracts sugars from the stem end to support leaf growth.
When the reducing sugars accumulate on one end of the tuber, the plant could start producing heat sprouts. These sprouts occur at the bud end of the tubers. Therefore, as the process resumes, plant hormones will reverse the vegetative growth.
Sugar end disorder results from high concentration of reduced sugars when a plant cannot convert sucrose to starch (due to heat stress). The disorder reduces your potatoes’ quality when it occurs during tuber formation or bulking. Therefore, if you’re growing your potatoes for french fries processing, they’ll turn black or brown due to low starch concentration on one end and a high amount of sucrose on the other.
High Nitrogen Fertility
Unfortunately, some beginner potato farmers aren’t as well-informed as they should be regarding how to balance macronutrients at different growth stages, so let’s address this here.
Macronutrients, including nitrogen, potassium, and phosphate, are essential during the growth and development of potatoes. However, you should know when to apply a specific nutrient and in what quantity for optimum yields:
Initial Growth Phase
When a potato plant is in its initial growth phase, it requires a good balance of the three macronutrients to promote vegetative growth. These elements are crucial in producing a strong stem with sufficient leaves to facilitate photosynthesis. The three nutrients also support an effective root system to anchor the plant and enhance the uptake of minerals from the soil.
Tuber Initiation & Bulking Phase
When the potato plant starts forming tubers and blooms, it requires more potassium. Likewise, as the tubers start enlarging, the plant will need a high concentration of potassium and phosphorus. Therefore, if you apply more nitrogen at this point, tuberization will slow down as canopy growth overtakes it.
Therefore, high nitrogen fertility during tuberization increases the concentration of gibberellic acid that promotes leaf growth. Contrastingly, it reduces the concentration of auxins and abscisic acid, slowing down tuber formation. Therefore, if this persists, there’ll be low or no formation of potato tubers.
Moisture Stress
Like all plants, potatoes need sufficient water to grow. Moreover, water is an essential requirement during tuber formation. Tuber initiation is the third phase of a potato plant’s growing cycle, and it determines the volume of yields in the plant.
Before planting your potatoes, the required soil moisture should be 70-80% field capacity (FC).
You can irrigate the soil to provide sufficient moisture and facilitate root formation. Pre-planting irrigation also helps break down clumped soil (or clouds) to ease planting.
However, you won’t have to water your potato seeds during and immediately after planting, as the seeds have enough moisture to sustain themselves. The recommended moisture level in the soil at this stage is 65-80% FC. Therefore, if you had irrigated your growing bed before planting, there should be enough moisture to support sprouting.
However, if you exceed the recommended moisture levels by overwatering your seeds, your potatoes will experience various issues. For instance, excess soil moisture will:
- Inhibit soil aeration and attract pathogens that cause bacterial soft rot or stolon and stem canker.
- Stress the seed piece due to decreased respiration.
Approximately three weeks after sprouting, the potato seed needs 70-80% moisture to initiate tuber formation.
This lengthy growth phase involves vine elongation, canopy growth, and tuberization. For this reason, you should start watering your plants from 0.5 to 1.5 inches (1.27 to 3.81 cm) weekly to sustain this phase.
Tuber formation starts with about 15 – 20 tubers per plant. However, due to increased foliage, the rate of transpiration also increases. This means that if there’s a moisture deficit (below 65%), fewer or no tubers will form, reducing the overall yield of your potato plants.
In the second stage of tuber formation, a potato plant needs about 80 – 90% of soil moisture FC. In some potato varieties, this is the full bloom phase when vine growth slows down, while in others, the growth stops.
It’s crucial to water your plants during this period since there’s a high transpiration rate, and moisture stress could cause tuber problems (such as sugar end disorder) and plant weakness.
In the last growth phase (tuber bulking), there’s an increase in tuber size and weight. However, not all formed tubers make it to this stage since some provide nutrients to the plant or are absorbed by the more competitive ones. Therefore, if moisture stress persists and few tubers have formed initially, your potato plant may end up with no tubers during harvest.
During the bulking phase, tubers need about 80 – 90% soil moisture for maximum growth. In short, the total amount of water from irrigation and rainfall should be 2 – 2.5 inches (5.08 – 6.35 cm) to meet this threshold.
The tubers (and the plant generally) are highly vulnerable to moisture stress. Therefore, moisture inadequacy impedes tuber growth and causes tuber malformations.
Moreover, the plant may also die due to diseases such as brown spot and early blight. There will always be some hazards that are out of your control; but what you can do is avoid over-watering your plants, as excess moisture could lead to water tot in tubers and vines or trigger late blight.
Use of Diseased Seed Potatoes
The type of seed potatoes you plant will significantly affect your yields. High-quality potato seeds are much more likely to produce healthy tubers.
If you’ve planted non-certified seeds, the chances that these seed potatoes could be diseased are higher than you’d think.
Most potatoes from your local grocery stores are treated with sprout retardants. Additionally, homegrown potato seeds may be more prone to pest and disease invasion.
Sometimes, using non-certified seeds is inevitable, especially if the variety you’re looking for isn’t readily available. Therefore, if you’ve bought your potato seeds from a supermarket or a similar, non-specialized establishment, you can first store them at room temperature to determine if they have any sprout-inhibitors.
If no sprouts emerge within 14 days, these seeds could be unfit for planting.
This is why experts recommend that potato farmers only plant certified seeds, as they’ve been pre-tested by professionals. Moreover, they’re proven to be free from diseases and sprout-inhibitors.
Certified seeds are also high-yielding, and you can expect them to produce potatoes unless other factors inhibit their growth.
Rushed Harvesting
How long did it take you to harvest your potatoes after planting?
The lack of tubers from your potato plants might have been due to early digging. Although the days to maturity differ among potato varieties, following the guidelines before harvesting is always advisable.
Some potato varieties, including Irish cobbler, Mountain rose, and Norland, mature fast and start producing tubers 50 – 80 days after planting. Others, including Viking, Red Pontiac, and Chieftain, are mid-season varieties that can take about 95 – 110 days to mature.
On the other hand, late varieties such as Elba, Kennebec, and Katahdin will be ready for harvest from 125 – 130 days post-planting.
Sometimes, wrong timing or poor choice of seed variety could lead to planting your potato seeds late. For instance, if you planted a non-certified variety, it’s difficult to determine the best time to plant or harvest its crops, which is why there’s a high chance that you’ll end up harvesting it earlier or later than necessary.
Harvesting your potatoes before they’ve matured could lead to disappointments if the tubers haven’t formed yet. Additionally, if the tubers are too small, exposing them to light might cause greening or sun damage. Therefore, it’s crucial to know the best time to dig up your potatoes.
Here are some signs that could indicate that your potato plants are ready for harvesting:
- When flowers open and buds drop in early potato varieties (around June): The “new potatoes” are ready for harvesting around 2 to 3 plants after they stop flowering. These varieties have a short shelf life, and people love them for their tender skin and convenient sizes.
- Yellowing or drying vines: Other potato varieties take longer and show maturity when the vines start dying.
- Temperature changes: Depending on your planting time, temperature variations can hint at the best time to harvest your tubers. For instance, if you planted the seed potatoes in fall (for winter storage), harvest the potatoes before the onset of the hard frost. However, despite the season, harvesting should occur when the temperatures are above 7 °C (45 °F).
How To Tell if Your Potato Plants Aren’t Producing Potatoes
Since potato tubers form beneath the soil, it’s difficult to tell whether their production is taking place or not. However, monitoring your plants could give you some hints on this phenomenon.
Therefore, when checking how your plants are growing, it’s crucial to identify any unusual signs.
You can get some clues on whether your potato plants produce tubers or not by observing their leaves. Some signs could indicate that the plants are diseased or not doing so well generally.
Here are the signs that could indicate that your potato plants aren’t producing tubers or there are tuber malformations:
- Very lush foliage
- Rolled-up leaves
- Stunted growth
Very Lush Foliage
The green color in plant leaves indicates chlorophyll (the green-coloring pigment), which is a good thing. However, overly green leaves might signify that your plant has high nitrogen fertility.
As mentioned earlier, this happens when you apply too much nitrogen during the tuber initiation stage.
The high nitrogen levels will trigger foliage growth but inhibit tuber formation. Therefore, if you notice that your potato plants are abnormally green, go slow on the nitrogen-based fertilizers. Early detection of any abnormality could help alleviate the poor tuber formation issue.
Rolled-Up Leaves
Another problem related to high nitrogen fertility in potatoes is rolled-up leaves.
Excessive application of nitrogen-based fertilizers will shift the plant’s focus on the leaves. Therefore, there will be increased activities and food distribution on the foliage at the expense of the roots.
Consequently, when this happens, the roots and other elements located beneath the soil (including tubers) will be neglected. Therefore, the plant will not initiate tuberization as all the nutrients will be geared towards foliage growth.
However, since the leaves are over-burdened with activities, they’ll eventually be stressed. Therefore, you’ll notice that the leaves are not only green, but they could start curling.
Moreover, the formed canopy could start yellowing or turning brown and eventually dry out due to the stress. Then, younger leaves are more likely to be pale green or yellow with green stripes and may be smaller than the older ones.
Stunted Growth
Unhealthy potato plants will have a hard time initiating tuber formation. So, if your plants appear very weak or has stunted growth, various plant processes (including tuberization) may not occur.
Delayed growth in potatoes can result from various factors, which include the following:
Waterlogging
Although potatoes require moisture (almost) all throughout their growth process, excessive water is detrimental to the plants. For instance, too much moisture when planting potato seeds leads to rotten pieces. Additionally, excess water during tuber initiation causes early death in potato veins before they’ve reached full bloom.
Pests and Diseases
Pests and diseases can cause stunted growth and slow tuber formation. For instance, early blight, caused by the Alternaria species, occurs in stressed plants due to water and nutrient inadequacy. Since water deficiency also affects tuberization, early blight symptoms on the leaves could also indicate that the plant is not producing potatoes as it normally would.
How To Prevent Poor Yields in Potatoes?
Every farmer’s dream is to have a bountiful harvest after planting and taking care of their plants. However, many scenarios, including those I’ve explored in this article, could lead to poor yields. Although some causes might be uncontrollable, there are some measures you can take to prevent this from happening.
To prevent poor yields in potatoes, use certified seeds, observe potatoes’ growing conditions, apply fertilizers appropriately, and ensure that your potato plants have sufficient moisture. Other ways of increasing potato production include preventing and treating pest invasion and diseases.
Now, let’s look at these prevention strategies in more detail:
Choose the Right Potato Seeds
As mentioned earlier, the type of potato seeds you plant will determine the volume of your harvest.
Therefore, consider using high-quality, certified seeds, as they are disease-free and have no sprout inhibitors. Additionally, choosing seeds that match your region’s climatic conditions will translate to a high yield.
Have the Best Growing Conditions for Your Potatoes
Potatoes are cold-season crops with specific requirements for optimal growth. Therefore, it’s crucial to know your plant’s ideal conditions if you want to optimize its yields. Potatoes require:
- The Right temperatures: The average growing temperature is 20 °C (68 °F). But, the foliage flourishes between 20 – 25 °C (68 – 77 °F), while the tubers form between 15 – 20 °C (59 – 68 °F).
- Good soil: Potatoes prefer loose, well-drained, and acidic soil (pH between 6 and 6.5).
- Optimum moisture: Potatoes require moisture throughout their growth. However, the highest moisture requirement is during tuber initiation and bulking.
Apply Fertilizers Appropriately
Potatoes can grow in moderately fertile soils. However, you can add fertilizers if your soil is nutrient-deficient. However, there should be a good balance of macronutrients to ensure that there’s uniform growth in all parts of the plants.
Generally speaking, the best ratio for the necessary macronutrients (nitrogen, potassium, and phosphorus) is 3:5:1.
Prevent and Control Pest Invasion and Diseases
Various pathogens attack potatoes, causing diseases such as early and late blight, Verticillium wilt, and potato scab. While some pests and diseases are preventable, it is difficult to control others – especially the soil-borne ones.
Avoiding plant stress by providing adequate moisture and nutrients can prevent early and late blight diseases. Moreover, hilling around plants can prevent sun damage and greening in tubers. Lastly, the use of certified seeds minimizes the occurrence of pests and diseases.
On the other hand, you can control the spread of pathogens and diseases in some scenarios. For instance, if your plants are experiencing an invasion by the Colorado potato beetle, you can regulate the infestation by hand-collecting the insects. Additionally, you can reduce aphid and flea beetle attacks by using insecticidal soap.
Conclusion
Your potato plant producing insufficient yields can be frustrating to any farmer. Your potato plants may fail to produce tubers if they’re facing some kind of stress. Therefore, it is crucial to identify the cause and prevent or control it to improve the plant’s yields.
