Hemp Morphology and Physiology Standards for Research and Industry Applications

Abstract

Hemp (Cannabis sativa L.) research and commercial production has recently experienced a global revival motivated by passage of laws reversing long-standing prohibitions and by expansion in markets. Collaborative research has been initiated in response to renewed interest in hemp production, such as the American Society for Horticultural Science Hemp Research and Extension Professional Interest Group (ASHS Hemp). Collaborators new to this crop have identified a lack of standard definitions, descriptions, and procedures for cohesive study specific to hemp production. Standards are necessary for synthesis of data gathered across research and industry programs. ASHS Hemp convened a workshop of hemp researchers and industry representatives to establish consensus on a minimum set of standards for research data and industry assessments. The resulting morphology and physiology standards developed at the workshop are presented here with a focus on plant height, flowering time, and crop quality. Plant height was defined as the vertical distance between the root crown at the soil surface and the stem node (or tip) of the apical meristem of the tallest branch. Plant height was importantly distinguished from stem length and canopy height, which may differ based on pruning and management of the plant. Flowering time was defined to indicate date of initiation of inflorescence development as the earliest day terminal flowering clusters appear visually. Flowering time was distinguished from solitary flowering behavior and floral maturity. Crop quality was determined to be a feature that should be established first by industry based on market standards and then subsequently adopted by researchers targeting outcomes in specific areas. A standard moisture content for dry flower, seed, and straw must be established. A moisture content of 10% to 12% was identified as a current standard for floral yield, whereas 8% was identified as a moisture content standard for seed crops. Bast-to-hurd ratio and decortication efficiency were fiber quality metrics identified for minimum standards, and thousand seed weight, protein content, oil content, and oil composition were considered for minimum seed quality standards. The hemp research community is well positioned to standardize genomic references and establish best management practices for production targets. These efforts would be assisted by the adoption of the proposed standard definitions, descriptions, and procedures decided by consensus at the ASHS Hemp 2022 workshop.