Supraoptimal Root-zone Temperatures Affect Dahlia Growth and Development

Dahlia ( ×hybrida ) is an important floriculture crop that has gained popularity in recent years. Greenhouse growers have recently reported a phenomenon known as “dahlia decline,” can affect potted dahlias greenhouse production. The exhibits graying foliage, root decline, and plant death, the reportedly caused partial or total loss no initiating factor. We hypothesized exposure to supraoptimal root-zone temperatures (RZTs) during production may decrease dahlia quality, especially above 40 °C could initiate decline. Because there lack of understanding on how RZT impact growth development, experiments were conducted evaluate effects RZTs seven cultivars Spring 2019 2020. Dahlias grown for 4 5 weeks then zones exposed ≈22 (control), 35, 40, 45, 50 using water bath. Root quality was rated before treatment weekly after hot bath treatment, along with vegetative parameters weeks. In both years, significant decline ratings observed. ‘XXL Veracruz’ Sunset’ average decreased 45 treatments year 2 demonstrated increased rating averages by 3 treatment. Cultivars exhibited increase final observations when compared taken 1 week posttreatment even if initial not significant. Overall height significantly impacted, resulting shorter heights years all comparison control 35 °C, few at °C. Ultimately, our research did show typical responses consistent but we better able characterize response RZT.