Grow Tube Material Selection Influences Thermal Microenvironments and Cold Hardiness Risk in Dormant Grapevines

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Abstract Background and goals Grow tube material selection plays a crucial role in shaping thermal microenvironments around young grapevines; however, quantitative guidance for selecting and removing grow tubes during winter months in cold climates remains limited. This study investigated how grow tube material and installation influence internal microclimates during dormancy, and the resulting implications for grapevine cold hardiness. Methods and key findings Temperatures were monitored across five grow tube treatments (paper and plastic materials installed at two configurations [buried and raised], plus a no-tube control) over two dormancy seasons. These in-field temperature data were used as inputs to a temperature-based cold hardiness model to simulate responses for four Vitis vinifera cultivars. Solar radiation drove material-dependent thermal differences: plastic tubes, acting as thermal storage systems, produced warming effects of up to ~3.40°C during cold, sunny afternoons, with buried plastic installations generating the highest internal temperatures. At night, temperatures in all tubes returned to near-ambient levels, resulting in larger diurnal temperature swings in plastic tubes than in paper or no-tube controls. Modeling showed that plastic materials had warmer midwinter hardiness thresholds (~0.10 to 0.30°C) and more rapid spring deacclimation than paper-based materials. In contrast, paper tubes enhanced chilling accumulation and maintained thermal profiles aligned with natural dormancy conditions. Conclusions and significance Overwintering vines in paper tubes without removal minimally affects dormancy temperatures and preserves chilling conditions similar to those in natural conditions. In contrast, overwintering in plastic tubes, particularly when partially buried, creates warmer daytime conditions that reduce chilling accumulation and may raise the risk of premature deacclimation in spring. This study provides insight into selecting grow tube material under continuous overwinter installation, balancing protective benefits with physiological risks during winter dormancy.