a potato inspector inspecting seed potatoes in a field

Understanding Seed Potatoes: classification, certification and quality

Embarking on the journey of growing your own vegetables can be a rewarding and fulfilling experience. If you’re planning to grow potatoes, understanding seed potatoes certification is crucial. In this comprehensive guide, we will delve into the world of seed potatoes, exploring their qualifications, the seed grading system used in the United Kingdom, and why certified seed potatoes are preferred for successful potato cultivation.

What are Seed Potatoes?

Seed potatoes are not your average potatoes purchased from the supermarket. They are specially selected tubers that serve as the starting point for growing high-quality potatoes. These potatoes are carefully chosen to ensure genetic consistency, disease resistance, and optimal growth characteristics.

Qualifications and Grades of Seed Potatoes in the UK:

In the United Kingdom, seed potatoes are classified into different grades, each indicating a specific stage of production and determining the duration for which the seed potatoes can be used for planting.

  1. Pre-Basic Grade: The seed potato production process begins with the pre-basic grade. Seed potatoes in this grade are produced for a maximum of five years (four years if grown in soil) from the original source material. The purpose of this stage is to ensure that the seed potatoes are free from diseases and pests, providing a healthy starting point for subsequent generations.
  2. Basic Grades (S, SE, E): After the pre-basic stage, seed potatoes progress to the basic grades, which include S, SE, and E. These grades represent the subsequent years of production. Seed potatoes in the basic grades undergo inspections to ensure that they maintain their quality and remain free from diseases.
  3. Certified Grade: Once seed potatoes have completed the basic grades, they move on to the certified stage. Certified seed potatoes are produced from the basic grade seed potatoes and undergo further inspections to verify their quality and health. This grade provides assurance to growers that the seed potatoes meet specific standards and have a reduced risk of carrying diseases or pests.
  4. Grade A: Grade A seed potatoes are considered the highest quality within the certified stage. They have passed stringent inspections and exhibit excellent health and genetic characteristics. Grade A seed potatoes are preferred by many growers due to their reliability and ability to produce robust potato plants.
  5. Grade B: Grade B seed potatoes are the final stage in the seed grading system. These seed potatoes have completed their life cycle and should no longer be used for planting. While they may still be edible, their quality and productivity for future crops may be diminished. Growers typically avoid purchasing or planting Grade B seed potatoes.

Why are Certified Seed Potatoes Preferred?

Certified seed potatoes offer several advantages over regular supermarket potatoes and other seed propagation methods:

plots of high grade seed potatoes grown on our farm
Plots of high-grade Pre Basic seed potatoes
  1. Disease Resistance: Certified seed potatoes undergo rigorous inspections to ensure they are free from diseases and pests. Planting certified seed potatoes reduces the risk of introducing harmful pathogens into your garden, providing a healthier start for your potato crop.
  2. Genetic Consistency: Certified seed potatoes maintain genetic consistency since they are clones of the parent plant. This means that the desirable characteristics of the potato variety, such as flavor, texture, and yield, are more likely to be retained.
  3. Higher Success Rate: Certified seed potatoes are carefully selected and produced under controlled conditions, ensuring their vitality and sprouting capabilities. Planting certified seed potatoes increases the likelihood of a successful harvest, with higher yields and healthier plants.

Choosing The Right Seed Potatoes:

When selecting seed potatoes, consider the grading system used in your region. In the UK, growers often opt for seed potatoes at the pre-basic grade, specifically in the S, SE, or E categories. These seed potatoes provide a remaining use of four or five years, offering optimal quality and productivity.

It is important to remember that as seed potatoes progress through the grades, their age and potential for lower productivity increase. To maximize your potato crop’s success, it is advisable to transition to fresher seed potatoes after the Grade B stage.

The Difference Between Seed Potatoes And True Potato Seeds

True potato seeds are acquired from the berries/fruit that develop after a potato plant flowers. These berries contain the true potato seeds, which are extracted by removing them from the ripe berries and drying them. The dried seeds can then be stored or germinated to grow potato seedlings.

However, growing potatoes from true potato seeds requires more time, effort, and expertise compared to using seed potatoes. True potato seeds are primarily used by plant breeders and researchers for developing new potato varieties and genetic studies.

Chitting and Planting Seed Potatoes

Chitting seed potatoes involves encouraging the seed potatoes to sprout before planting to potentially accelerate growth. To chit seed potatoes, select healthy tubers, position them with the rose end facing up, and allow them to sprout in a well-lit area.

When planting, prepare the soil, dig trenches or holes, place the chitted potatoes with sprouts facing up, cover them with soil, and provide proper watering and care.

The time for potatoes to grow and be ready for harvest ranges from 10 to 20 weeks, depending on the variety and growing conditions. Harvest mature potatoes when the foliage has died back or turned yellow.


Seed potatoes play a vital role in successful potato cultivation. Understanding the qualifications and grading system associated with seed potatoes helps growers make informed decisions about the quality and age of the seed potatoes they choose for planting. In the United Kingdom, the seed grading system encompasses the Pre-basic, Basic, and Certified grades. The Basic grades seed potatoes are the preferred choice for ware growers due to their disease resistance, genetic consistency, and higher success rates.

By selecting and planting certified seed potatoes, vegetable growers can set the foundation for a healthy and productive potato crop. Embrace the use of certified seed potatoes, follow local guidelines and certifications, and enjoy the satisfaction of cultivating your own delicious homegrown potatoes.