Why Are My homegrown Potatoes So Small? (7 Reasons with Solutions)

Potatoes are one of the staple foods grown by homesteaders around the world.  We plant the seed potatoes in the spring, water them, feed them and watch the plants grow and flourish, but we don’t know how good the harvest is until we start to dig the plants up.  If you have a poor harvest, you may be left wondering ‘Why are my homegrown potatoes so small?’

There are a number of reasons your homegrown potatoes are so small, and these include;

  • Lack of water
  • Under fertilized
  • Seeds planted too close together
  • Exposed to high temperatures
  • Poor quality seed potatoes
  • Potatoes were harvested too early
  • Not enough sunlight

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Potato Plants Received A Lack Of Water

For potato plants to grow well and produce a large crop of well-developed tubers, they require regular watering during the entire growing season, but especially when the potatoes themselves are developing and swelling. 

When potato plants don’t receive regular watering, the plants can dry out, or they may fail to absorb nutrients from the soil, meaning they don’t bulk up the tubers.

Potatoes grown on light, sandy soils require more water than potatoes grown in heavier soils.  Light, sandy soils drain much faster than heavier soils so require more water.

Solution:

If your potatoes may be suffering from a lack of water, there are a few things you can do to prevent the problem in the future. 

Firstly,  digging in plenty of well-rotted manure or homemade compost prior to planting the seed potatoes will improve the soil’s ability to hold water in the first place, meaning less water is required generally.  

Secondly, mulching around the potato plants as they grow will prevent moisture from being lost through evaporation.  Homemade compost makes a great mulch, as do fresh grass clippings, straw, or even plastic sheets.

An added advantage of mulching around your potato plants is that it reduces the chances of the potatoes going green due to exposure to light.



Potato Plants Were Under Fertilized

The potatoes we harvest and enjoy eating are actually the potato plants’ way of storing energy for future use.  To store up all that excess energy, the potato plants need to be properly fertilized.  When under fertilized, the potato plant may produce small potatoes.

To grow a good harvest of potatoes, potato plants require a mixture of the three main nutrients which are nitrogen, phosphorus, and potassium (also known as NPK)

Nitrogen helps the potato plant grow strong leafy sections.  Nitrogem helps build leaves and stems and all the green sections of the plant.  When we have potato plants that are looking yellow, it is often due to a lack of nitrogen.

Phosphorus is responsible for helping the proper development of roots, flowers, and fruits in plants.  Phosphorus affects the way the develops and how well it functions.

Potassium is responsible for keeping the potato plants healthy and contributes to the overall vigor of the potato plants.  Having a proper amount of potassium available to the potato plants helps their ability to fight off pests and diseases.

Solution:

Adding an appropriate amount of fertilizer over the growing season will help prevent your potato plants from being undernourished and developing very small potatoes.

When I fertilize my own potato plants, I use a 10-10-10 fertilizer, which means it contains an equal quantity of nitrogen, phosphorus, and potassium (NPK).

A recent study showed that the majority of new homesteaders were not adding enough fertilizer to their potato crops. 

The problem is, there is no easy way to determine how much fertilizer your potato plants require by just looking at them.  I use a soil test kit that I picked up from Amazon.  Soil test kits are an easy way to determine what nutrients are already present in the soil and therefore what needs to be added for optimal growth.

Seed Potatoes Are Planted Too Close Together

Potato plants are hungry plants that draw a lot of nutrients out of the soil.  Their top growth is tall and bushy and needs some space to spread out.

It is extremely common for homesteaders to try to cram as many potatoes into a plot as possible.  There is a common misconception that the more plants you squeeze into a space, the more potatoes you will harvest.  

When seed potatoes are planted too close together, the resulting harvest can be either a small crop of good-sized potatoes or more likely, a large crop of very small potatoes.

Solution:

Seed potatoes should be planted approximately 12″ (30cm) apart and in rows which are 24″ (60cm) apart if they are early potatoes or 15″ (40cm) apart and in rows which are 30″ (75cm) apart if they are maincrop potatoes.

When I plant out my seed potatoes I am always over-generous with spacing.  I like to be able to walk between my rows so I can check my crop on a regular basis.



Potato Plants Got Too Warm

Potatoes are a cool-weather crop.  They grow best when the soil is consistently at a temperature of between 60°F and 70°F (15°C and 21°C). 

Research has shown that the tubers may fail to form altogether if the soil temperature reaches 80°F (26.5°C).

Growing conditions tend to be more favorable for those living in the northern states, than those living in the warmer states of the south.

Having a prolonged warm spell during the growing season may be the primary reason for a small crop of homegrown potatoes.  A period of just two or three weeks when the soil temperature rose can be enough to prevent a decent-sized crop from forming.

Solution:

Like when it comes to making sure your potatoes got enough water, mulching the soil can help prevent the temperature of the soil from rising too high, especially if a thick mulch was applied.

If you have a small potato patch, using a shade cloth suspended on posts may just help keep the soil temperature down.

Poor Quality Seed Potatoes

Starting your potatoes off from poor quality seed stock can have a direct effect on the quality of the harvest your pull up at the end of the growing season. 

I know from personal experience, that it can seem like a great money-saving idea to take a few potatoes from the store and plant them in the garden.  They will work out far cheaper than a small sack of seed potatoes. However, in the end, you will pull up a poor-quality harvest.

Solution:

If you are serious about growing a crop of potatoes to be able to feed your family, you must buy quality seed potatoes that have been grown, harvested, and stored specifically for the purpose of growing potatoes.

In recent years I have had good success buying my seed potatoes from Amazon.  Every year it seems there are more and more varieties to choose from and by checking the reviews you can quickly see which merchants offer the best quality stock.

Potatoes Were Harvested Too Early

It may seem obvious at first, but harvesting potatoes too early will lead to tubers that are too small. 

Potatoes are the potato plants’ way of storing energy for the next season.  The longer the plants are growing the more energy they will save up for next year. 

Early Potatoes don’t need to be in the ground as long as Maincrop potatoes do.  Common wisdom says that Early Potatoes are ready for harvesting between 2 and 3 weeks after the plants stop flowering.

Maincrop potatoes do need to be in the ground longer than Early Potatoes.  Maincrops should be left until the foliage for the plants begins to die back.  

Whichever variety I am growing, I tend to dig up a single plant first, evaluate the size of the crop, then decide if the rest of the potatoes can be lifted.  On occasions when I have felt my Early potatoes were too small, I have left the remaining plants in the ground for another week or two.

With Main Crop potatoes this doesn’t work so well, as the plants have usually died back completely before I start lifting.

Potato Plants Didn’t Get Enough Sunlight

As discussed above, the potatoes we harvest are the plant’s stored energy for use the following year. To generate that stored energy the potato plants need access to sufficient sunlight.

To ensure we don’t end up with a crop of puny potatoes it is important to make sure our plants have access to enough sunlight.  

Whilst we can’t control the amount of light the sun graces us with, we can make sure our plants are not shaded out.  

The first year I grew potatoes I grew them in a patch which was shaded by 2 large oak trees.  It meant some of my potato plants only received full sun about 2 hours a day. There was a noticeable difference in the potato yield from those plants than others in the row.

Solution:

Firstly, make sure you plant your seed potatoes in a plot that is not shaded by surrounding trees or bushes.

Secondly, don’t plant your seed potatoes too close together.  The closer the potato plants grow to one another, the greater the chances they will shade one another out.


Arya Patel

Arya Patel is HomesteadSavvy.com’s fruit and vegetable editor. Arya has been homesteading for well over a decade and over that time she has grown countless varieties of fruits and vegetables. She aims to become completely self-sufficient over the next 5 years.
Fruit & Vegetable Editor