The Cultivar Check Program: Utilizing the Midwestern Hemp Database (MHD) and Grower-Cooperators to Assess Variety Performance of High Cannabinoid Hemp

Progress report for ONC23-117

Project Type: Partnership
Funds awarded in 2023: $49,339.00
Projected End Date: 04/04/2025
Grant Recipient: University of Wisconsin-Madison
Region: North Central
State: Wisconsin
Project Coordinator:
Phillip Alberti
University of Wisconsin-Madison
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Project Information


As a “new” crop to North Central agriculture, best management practices and performance of high cannabinoid industrial hemp (Cannabis spp.) varieties are still being investigated. Despite tremendous interest across the region, the lack of university published resources greatly increase the risk of hemp production relative to conventional crops and threaten to undermine the nascent hemp industry.   

To address these issues The Midwestern Hemp Research Collaborative (MHRC), a joint effort of land grant universities, non-profits, and private laboratories, was formed. Our proposed project will build on existing researcher-farmer partnerships to conduct participatory hemp cultivar trials to rapidly generate relevant, research-based information for the hemp industry. All data generated will be integrated into the Midwestern Hemp Database (MHD), a public online resource supporting stakeholder decision-making and risk mitigation.   

Outreach will be designed for growers and shared as part of a coordinated outreach plan, including the MHD website, written reports, presentations, and field days.  

Project Objectives:

1. Grow the MHD to include over 250 participating growers in 2025 across the NCR; Improve current visualization platforms for enhanced utility by stakeholders.

2. Reevaluate and modify “good potential” criteria to include additional factors including  photoperiodism, genetic uniformity, earliness and disease resistance.

3. Expand existing network of grower-cooperators (32+) conducting participatory on-farm trials using select “good potential” cultivars (20+) via the Cultivar Check Program; data to be included in the MHD; Improve data collection and data analysis/evaluation for enhanced utility by grower-cooperators. 



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Materials and methods:

1. Grow the MHD to include over 250 participating growers in 2025 across the NCR; Improve current visualization platforms for enhanced utility by stakeholders. 

From 2020 through the date of this writing, 286 hemp growers across the NCR contributed to the Midwestern Hemp Database. Crop management and variety performance data submitted by NCR hemp growers and variety trial participants were used to populate the MHD.  This public database provides timely data from commercial producers to support farmer decision-making.  Data is anonymized and aggregated to protect participants.  Specific protocols for agronomic data collection and floral sampling are distributed to participating growers who submit samples to partnering laboratories for analysis at a discounted rate. Using this approach, we can ensure the integrity of perhaps the most important and sensitive data for hemp growers: cannabinoid profiles. USDA sampling guidelines are followed and sent to participating, approved laboratories.

2. Reevaluate and modify “good potential” criteria to include additional factors including  photoperiodism, genetic uniformity, earliness and disease resistance.

"Good Potential" Criteria were originally developed to provide a baseline for cultivars being entered into the program. Given the lack of information about cultivar performance and sheer number of cultivars available, this allowed us to make informed selections. At the time of project inception, criteria were simple and left room for improvement, predominantly using total cannabinoid production and expected flowering dates as key indicators. After two years of this project, our research team is working with growers to develop a constantly evolving list of criteria to help growers make informed decisions. As of this writing, the criteria used to determine "good potential" cultivars are as follows: 

  • Demonstrates compliance through (or following) week 5 of flower development
  • Demonstrates an average overall performance rating of 3.5 or higher
  • Has been evaluated in the Cultivar Check Program for at least two years with n>5 at each time point 

We hope to continue to improve these criteria as growers and researchers needs change with this ever-evolving industry. Of particular interest is utilizing photoperiod and latitude to help inform grower decision making on a state by state basis.  

3. Expand existing network of grower-cooperators (32+) conducting participatory on-farm trials using select “good potential” cultivars (20+) via the Cultivar Check Program; data to be included in the MHD 

Farmers will be involved in our project by conducting their own on-farm variety trials and contributing data to the Midwestern Hemp Database. Allowing growers to choose which verified varieties they want to grow allows them the freedom to experiment while contributing to a large data set at a discounted rate. Growers will also contribute further by sharing their experiences through outreach events and resources

To complement data being submitted by NCR hemp growers and strengthen the tool,  5+ growers per state will be recruited to conduct participatory on-farm variety “checks” including a consistent subset of high-potential varieties determined using results from university and grower-cooperator variety trials. For on-farm trials, our team will supply seed/transplants/clones and cover the costs of cannabinoid testing. Growers will submit management, performance, and economic data via an online survey using the SeedLinked platform, as well as flower samples for cannabinoid analysis by partnering laboratories.  Grower data collection will emphasize experiential and qualitative information to complement the quantitative information generated by ongoing, coordinated university trials.  Participating growers will contribute to the development and delivery of outreach events and resources such as field days, conference presentations, and webinars.

Licensed hemp growers across the Midwest (Michigan, Illinois, Indiana, and Wisconsin) were recruited to participate in the Cultivar Check Program. Each grower received a subset of cultivars consisting of CBD Dominant (Chemotype 3) and/or CBG Dominant (Chemotype 4) cultivars. Seedlings were established in late April or early May in indoor/greenhouse settings, and were allowed to develop in a greenhouse/hoop house for 4-5 weeks prior to a “hardening-off ” period. Following a one week hardening-off period ~15 healthy, representative seedlings from each cultivar were transplanted into the field in mid-June. Growers were responsible for submitting various management and performance data via an online survey using the SeedLinked® platform. The following traits were rated on a scale from 1 to 5 using a semi-quantitative guide to help cooperators with their ratings: 

Seed Start and Transplant Date

  • The dates at which the plants were started in the greenhouse/indoor environment and transplanted into the field, respectively.


  • A visual rating of germinative capacity within a cultivar (1= poor, 5= excellent).

50% Flowering Date

  • The date at which half of the plants of a given cultivar had visibly initiated terminal flowering (extruding stigma at its apical (top) inflorescence.


  • A visual rating of the uniformity of plants within a cultivar (1= not uniform, 5= very uniform)

Overall Performance

  • A visual rating of the overall performance of plants within a cultivar (1= poor, 5= excellent)

In addition to agronomic performance data, growers were required to submit floral samples for cannabinoid analysis at three time points: 3 weeks, 5 weeks, and 7 weeks (~21 days, 35 days, and 49 days, respectively) after the 50% flowering date. Before submitting flower samples, growers submitted pictures of plants to establish flowering dates. Flowering was confirmed by one of the project collaborators and a sampling schedule was developed. For sampling, growers followed the USDA sampling guidelines, collecting 5-8 inches of floral tissue from the top third of 5 plants for each cultivar at each sampling time point. The 5 flowers were placed into one bag to generate one composite sample per cultivar at each time point. Floral material was sent to Rock River Laboratories (Watertown, WI) for analysis of cannabinoid potency using high-performance liquid chromatography (HPLC).  Total THC = Δ9 THC + (THCA*0.877), Total CBD = CBD + (CBDA*0.877), and Total CBG = CBG + (CBGA*0.877).

Research results and discussion:

Across the 2021, 2022, and 2023 growing seasons, a total of 322 grower-cooperators participated in the Cultivar Check Program and Midwestern Hemp Database Projects.  Of those who participated, 36 grower cooperators (58 site-years) evaluated 39 different hemp cultivars for agronomic performance and cannabinoid development. As a result, the information synthesized from these trials marks a significant increase in regional hemp knowledge and is an important step towards successful adaptation of hemp as a viable option for Midwestern farmers.

Total THC and Total CBD were impacted by cultivar and sampling period (P < 0.05). Cannabinoid data is presented as averages across all locations at each time point. THC and CBD increase as flowering progresses, with cultivars exhibiting varying optimal harvest intervals for both compliance (THC) and profit potential (CBD). Many, if not most, CBD dominant hemp cultivars currently on the market will go “hot” (Total THC >0.3%) if not monitored appropriately during flowering. To illustrate, 25 (66%) of the 38 cultivars in the check program exceeded the regulatory limit at some point during the flowering period.

Data from the 2021, 2022, and 2023 growing seasons has been utilized to develop estimated compliance harvest/ sampling schedules based on 95% confidence intervals for Total THC (%). Cultivars are subsequently broken down into the following categories based on the findings:

  • Compliant Prior to Week 3 (Red)
  • Compliant Through Week 3 (Orange)
  • Compliant Through Week 5 (Yellow)
  • Compliant Through Week 7 (Green)

The ratio of CBD to THC concentration (CBD:THC) is impacted by cultivar and sampling period (P<0.05). As such, cultivars were evaluated individually and CBD:THC is presented in terms of averages across all locations at each time point. CBD:THC of many of the hemp cultivars were unaffected by sample timing, remaining consistent throughout flowering. Similarly, CBD:THC was unaffected by grower location, remaining consistent across environments. This supports previous work by researchers from Cornell University showing that CBD:THC remains stable throughout flowering for uniform cultivars. Total CBD (%) infrequently exceeds ~8% without exceeding the regulatory threshold of 0.3% Total THC, resulting in a CBD:THC of ~27:1. Considering this, cultivars with a stable CBD:THC  throughout flowering will help to maximize profitability while maintaining compliance.

For each cultivar, cannabinoid development was impacted by sampling period and location/environment (P<0.05). As such, cannabinoid data is presented in the following manner for each cultivar: Total THC (%) and Total CBG (%) are presented in terms of averages across all locations at each time point. THC and CBG increased over time, with cultivars exhibiting varying optimal harvest intervals for both compliance (THC) and profit potential (CBG). None of the three CBG dominant cultivars exceeded the THC threshold for compliant hemp by the week 7 sampling period. Similarly, across the entire MHD data set, average Total THC (%) of CBD dominant cultivars was 0.258 compared to 0.075 for CBG dominant cultivars. CBG dominant cultivars may provide an alternative cropping option for those looking to reduce risk of non-compliance compared to production of CBD dominant cultivars.

Flowering data are presented as the Julian Calendar Date at which a cultivar was deemed to be flowering.  Results of the ANOVA show that flowering date was significantly impacted by cultivar and location (P > 0.05). Across all cultivars, the mean 50% flowering date was day 226 or August 15th. Cultivars were subsequently grouped into maturity groups (early and late) based on mean expected flowering day. Agronomic performance ratings (germination, uniformity, overall performance etc.) are given as averages across all environments for each cultivar. These ratings will not be analyzed for statistical significance given the subjective nature of the qualitative ratings and are meant to guide future research trials and cultivar selections only. University station trials may be more useful/accurate sources of information for yield metrics and will not be discussed here.

Growers will want to consider the following factors when making variety selections in their region:

  • Seed Quality (Germination, Uniformity, etc.)
  • Maturity Group (Photoperiod)
  • Agronomic Performance (Yield and Quality)
  • Cannabinoid Development (Compliance Potential)

Seed certification standards in the hemp industry are still being developed. Growers are encouraged to develop relationships with seed providers and to look to university published resources to guide their selections. Seed providers should provide seed testing data (germination, dormancy, noxious weed presence, etc.) but growers may also wish to look to local seed certifying agencies (such as crop improvement centers or departments of agriculture) to find cultivars which have either been certified or are in the process of becoming so. AOSCA provides an updated list of cultivars eligible for certification, which can be found on their website (

Growers will want to consider maturity group when making variety selections. For example, growers in northern latitudes may want to plant earlier maturing cultivars to maximize the shorter growing season compared to their southern counterparts. It should be noted that some cultivars exhibit heterogeneity across and within cultivars which can make agronomic performance and cannabinoid development less predictable. Due to the non-uniformity of the flowering process, unstable/non-uniform cultivars could reach maturity at different points in the growing season, which could have adverse impacts on testing and harvesting strategies at the field level. As such, growers may want to consider uniformity of growth and development of plants within a cultivar when making selections to avoid compliance concerns.  

Importantly, cultivars with a history of certification or compliance may not be agronomically suited to a region while some cultivars with a history of high performance may not be reliably compliant. To better understand cultivar agronomic performance in a similar region, growers are encouraged to access local university cultivar trials for the most accurate regional information. Similarly, growers are encouraged to access the MHD for the best information available regarding compliance potential of evaluated cultivars. Using the information from both of these sources will allow growers to make informed decisions.

As cannabinoids do not begin to develop rapidly until flowering has initiated, growers are encouraged to delay sampling until after terminal flowering to eliminate unnecessary testing costs. Compliance with state, federal, or tribal regulations is determined by showing that each hemp lot produces Total THC <0.3%. Under the current final rule, no more than 30 days prior to the anticipated harvest of cannabis plants, a “sampling agent” must collect samples for compliance testing. If producers do not harvest within 30 days of sampling, the lot must be retested prior to harvest, and the plants will likely have a higher THC level at harvest than the initial sample. Growers will want to consider their cultivar’s cannabinoid development following flower initiation in conjunction with this 30-day window from sampling to harvest to maximize profitability while maintaining compliance. Lastly, there is currently a great deal of variation across sampling, sample handling, laboratory sample preparation and analytical methods. This disparity between current field and laboratory procedures makes cannabinoid results difficult to compare. As such, using USDA/state approved sampling methods and submitting samples to an approved, accredited laboratory is recommended.

Participation Summary
322 Farmers participating in research

Educational & Outreach Activities

120 Consultations
3 Curricula, factsheets or educational tools
3 On-farm demonstrations
10 Webinars / talks / presentations
3 Workshop field days

Participation Summary:

900 Farmers participated
6 Ag professionals participated
Education/outreach description:

Select outputs (journal articles,  research reports, and presentations) have been created annually. Research reports for this project are shared via grower-cooperator networks and posted to university webpages. 

During the winter/spring educational season, results of the Cultivar Check Program and Midwestern Hemp Database are shared at various conferences, seminars, and workshops. 

Growers met biweekly during the growing season to perform continued education efforts and encourage discussion/program improvement. 

During the growing season, educational events/webinars were hosted regularly to update program participants and stakeholders on our research efforts. 

Consultations are provided regularly for growers looking to utilize data for this project on their operations. This includes making variety selections in addition to providing insight on sampling and harvest recommendations. 

Learning Outcomes

225 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key changes:
  • Variety and Cultivar Selection

  • Risk Management

Project Outcomes

36 Farmers changed or adopted a practice
4 New working collaborations
Project outcomes:

Participating researchers and farmers will learn/identify suitable hemp varieties and production strategies in the NCR

Participating researchers to learn/identify various laboratory analytical methods and interpretations across states in the NCR

Participating researchers to learn general principles of on-farm trials to incorporate into other aspects of their farm 

Industrial hemp producers and processors may use the database to influence decisions regarding hemp variety selection, production strategies, and harvest schedules 

Industrial hemp producers and processors to utilize information from laboratory proficiency programs to inform decision-making regarding laboratory selection and interpretations of laboratory analysis. 

Information Products

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.