Certified seed potatoes: what they are and how to buy them
Certified seed potatoes are seed tubers that an official authority has inspected in the field and in the store and found within the disease and purity limits of their grade. Buying certified seed is the main protection a grower has against viruses and blackleg arriving with the seed. This page explains what the label guarantees, the EU grades A and B, who exports certified seed, and how to buy seed potatoes from a certified source.
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What are certified seed potatoes?
Certified seed potatoes are seed tubers that an official certification authority has inspected in the field and as a harvested lot, and found within the limits set for their grade. The limits cover off-type plants (wrong variety), blackleg, virus symptoms and tuber defects such as rots and scab. The label names the grade, so a buyer knows what the lot was tested against.
Certified seed is the last step of the seed ladder, the class sold to growers to plant ware, processing or further seed crops. Higher classes (pre-basic and basic) are kept for multiplication.
How seed is multiplied is on the seed potatoes hub; the inspection process is answered in seed potato certification.
What do EU grades A and B allow?
In the European Union, certified seed potatoes are marketed as Union grade A or Union grade B (Commission Implementing Directive 2014/20/EU). Both are checked twice over: the growing crop and its direct progeny must meet the plant limits below, and the marketed lot must meet the tuber limits.
| Limit (maximum share) | Grade A | Grade B |
|---|---|---|
| Off-type plants and other varieties | 0.2% | 0.5% |
| Blackleg in the growing crop | 2.0% | 4.0% |
| Plants with virus symptoms in the direct progeny | 8.0% | 10.0% |
| Mosaic or leaf-roll symptoms in the growing crop | 2.0% | 6.0% |
| Rots in the lot (other than ring rot and brown rot), by mass | 0.5% | 0.5% |
| Black scurf over more than 10% of the surface, by mass | 5.0% | 5.0% |
Source: Commission Implementing Directive 2014/20/EU, Annex II (EUR-Lex). Ring rot and brown rot are governed by EU plant-health law, not by these tolerances.
Outside the EU the names differ but the logic is the same. Western Australia caps seed at five field generations from laboratory or glasshouse generation zero, and any generation that meets the standard may be sold as certified (DPIRD, Aug 2023).
How to buy seed potatoes from a certified source
- Ask for the certificate or official label for each lot: it names the variety, the grade or generation and the lot number. In the EU the grade reads "Union grade A" or "Union grade B" (Directive 2014/20/EU).
- Check the supplier and the lot with your national seed certification authority.
- Order by variety, class or generation, and tuber size (Potatopedia growing guide).
- For imports, check your country's plant-health import rules for seed potatoes before you order.
- Avoid shop potatoes as seed: they can carry viruses such as PVY and PLRV without symptoms (Potatopedia growing guide).
Looking for seed potatoes for sale? Use the Find certified seed form below: tell us the variety, quantity and planting month.
Who sells the most seed potatoes abroad?
The Netherlands exported 922,273 tonnes of seed potatoes worth US$802.4 million in 2025, followed by France (275,531 tonnes, US$173.4 million) and Germany (120,842 tonnes, US$95.7 million). The United Kingdom, Belgium, Denmark, Canada, Egypt and the United States complete the top nine by value (World Bank WITS / UN Comtrade, 2025, HS 070110).
The full table is on the seed potatoes hub; country detail is in the Netherlands profile.
Find certified seed
Tell us what you want to plant, how much and when. We reply with certified sources for your country.
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Sources
- Commission Implementing Directive 2014/20/EU (Union grades of basic and certified seed potatoes), EUR-Lex
- World Bank WITS / UN Comtrade, seed potato (HS 070110) exports by country, 2025
- DPIRD Western Australia, Certified Seed Potato Scheme production rules (SPP-1 Issue 8, Aug 2023)
- Potatopedia, common potato growing mistakes (seed checks)