Potato Seed Certification Service

We’re glad your here. This directory is provided by the Colorado Potato Certification Service, located at the San Luis Valley Research Center in Center, Colorado and is prepared and updated annually by the Colorado Certified Potato Growers Association, Inc., in cooperation with Colorado State University. Seed potatoes are certified in Colorado through authority granted by the Colorado State Board of Agriculture. 

The Potato Certification Service and the Colorado Certified Seed Potato Growers sincerely hope the 2020 Seed Potato Directory will be helpful to seed buyers. We realize, however, that some individuals may want additional information.  Please contact the potato certification service or individual seed growers…We’ll do our best to help!

About the 2020 Certified Seed Directory

Listed are those growers with potatoes produced for the 2020 crop qualifying for certified seed. Included in the directory are acreage of cultivars approved following field inspections (storage inspections will be completed after harvest), lot identification, generation, and final inspection field readings. Cultivars with acreage less than 0.10 total or private cultivar upon owners’ request are not listed. Feel free to inquire from any grower listed about additional information you believe may be of assistance in evaluating their seed lots. The seed grower can verify that any given seed lot you may wish to purchase has been stored separately. It sometimes becomes necessary for seed growers to store similar seed lots of the same cultivar in a single bin which could result in loss of the individual lot identity listed herein.


Re-Certification Conditions

Not all certified seed will be eligible for re-certification. ONLY THOSE LOTS MEETING POST HARVEST TEST REQUIREMENTS OR OTHER STANDARDS WILL BE APPROVED FOR RE-CERTIFICATION. A supplementary list will be available following completion of post harvest testing to identify eligible lots.


Any lot(s) of seed proven to be infected with bacterial ring rot or otherwise unfit for seed will be rejected for certification regardless of the time or place of inspection.

Certain Colorado regulations may additionally limit the eligibility of seed lots for re-certification. Please note the following explanation which identifies seed lots that are affected by these regulations.

Preceding each grower’s name in the Directory is a space which may be blank or have an asterisk (*). The same symbol is located immediately preceding lot identity in the main body of the Directory.

Blank – The grower’s lots listed passed all field inspection requirements and are approved as certified seed. All lots are eligible for re-certification contingent upon required storage inspection and post harvest test results.

* – The grower’s lots listed passed all field inspection requirements and are approved as certified seed; however, this grower had a lot(s) of seed potatoes in his farming operation rejected due to bacterial ring rot. Any seed lot with an * in its designation shall not be eligible for re-certification the following year except by the original grower or the farming operation where bacterial ring rot was identified. The * symbol will also be printed on all of the grower’s tags and bulk certificates.

Please Keep These Designations in Mind When Utilizing This Directory

Blackleg Field Readings

Blackleg field readings are included in the Colorado Seed Directory in response to numerous requests from seed buyers. Although estimates of blackleg percentages are routinely collected by field inspectors, this data is not necessarily a reliable indicator of blackleg in the crop grown from any given seed lot. Environmental conditions and cultivar response to infection can either magnify or suppress blackleg symptom expression sufficiently to prevent a reasonable correlation between the seed source reading and the next crop grown. These field readings, however, may be a useful indicator of blackleg reinfection into seed lots originating from laboratory produced, tissue-culture propagated stocks.

Line Selections

The Potato Certification Service verifies that each cultivar listed in this Directory has been correctly identified. Some individual seed growers, however, may have developed or obtained from another source, line selections that possess characteristics such as yield potential, maturity, vine and/or tuber type that could be different from any given cultivar as originally described and named. Since such characteristics cannot usually be verified on a reliable basis by conventional certification methods, the responsibility for informing the seed buyer about line selection characteristics rests with the seed grower. Therefore, seed purchasers are urged to consult with the seed grower about line selections that may be included (but not identified) among the seed lots listed.

Decimal Percentages Used in Reporting Field Readings

The field reading percentages used in this Directory are calculated from actual plant counts made visually by inspectors when they walk through the fields. The number of diseased, or otherwise undesirable plants accumulated in any given inspection are divided by the total number of plants observed. The numerical result is a decimal percentage. To help you visualize decimal percentages to actual frequency of diseased plants in a field, it is helpful to express it in terms of diseased plants per 10,000. The table below illustrates how decimal percentages relate to plants per 10,000.

Field Reading PercentDiseased Plants per 10,000 

Explanation of Generation Symbols

Lab and/or Greenhouse Production 
Lab tested; tissue-culture or stem-cut propagations; plantlets, microtubers,
or greenhouse produced minitubers.
1 (G1)
2 (G2)
3 (G3)
4 (G4)
5 (G5)
6 (G6)
Field Production
First year of field production (planting from nuclear stocks)
Second year (G1 planting)
Third year (G2 planting)
Fourth year (G3 planting)
Fifth year (G4 planting)
Last year of field production (G5 planting). G6 stocks cannot be re-entered
for certification.
Non-Generation Certified (NGC)Planted from certified stocks of cultivars for which tissue-culture derived, lab< tested seed sources are temporarily not available. NGC stocks must meet qualifications for re-certification and are inspected and classified according to the disease tolerances and all applicable rules and regulations established for G6.
Includes unnamed “seedling” clones (Please see Special Requirements for Experimental Class Seed Potatoes in the appendix of this Directory).

Explanation of Lot Number Designations

Each lot number consists of several parts. For example, the following lot number “17020ATL41” consists of…

17 = 2017: the year of production
020 = Scidmore Farms: the grower’s individual ID number
ATL = Atlantic: the cultivar designation
4 = generation 4: the generation of the seed lot
1 = the first lot of generation 4 Atlantic seed on grower ID 008: The number of individual lots of that particular cultivar by generation. There may be more than one lot of a particular cultivar by generation. Numbers would progress; 2, 3, 4, etc. based upon the actual number of similar lots on the grower’s farm.

We hope this explanation will clarify how each lot number is derived.