2019 ASHS Annual Conference

Graphically tracking poinsettia crops is a valuable tool to guide grower management of crop height. As new poinsettia cultivars have replaced those that were used to generate the target ranges for the original graphical tracks, updates are warranted. In addition, cultivar responses to production factors such as plant growth regulator (PGR) applications and late season stretch can be incorporated into versions of graphical tracks to aid growers in anticipating plant response. Euphorbia pulcherrima ‘Ferrara’, ‘Holly’, ‘Premium Marble’, ‘J’Adore Pink’, ‘Prestige’, ‘Titan Red’, and ‘Christmas Spirit’ were potted in 6.5-inch pots and grown in two DIF environments (+5 and +9) during Falls 2017 and 2018. All plants were tracked bi-weekly until harvest. Effect of a range of application rates of PGRS on growth curves were evaluated on both ‘Ferrara’ and ‘Titan Red.’ Interestingly, our results suggest that the current S-shaped graphical track could be optimized to better represent the growth curves of these poinsettia varieties when grown in either +5 or +9 DIF environments. A strategy for growers to minimize the complexity of managing graphical tracking of multiple cultivars is to use standard curves across three vigor groupings (low, moderate, and high) suitable for the wide range of poinsettia cultivars available in the market today.