Water management and soil fertility can influence not only sweet cherry productivity during the growing season, but also the ability of flower buds to withstand low temperatures during the autumn-winter period.
This is what emerged from a recent study conducted in a commercial sweet cherry orchard in British Columbia, Canada, on ‘Skeena’ sweet cherry trees grafted onto Gisela 6, in which the combined effects of irrigation method and the use of organic soil amendments on bud cold hardiness were evaluated over two seasons.
The comparison involved drip irrigation and microsprinklers, both managed to replace evapotranspiration, combined with three soil conditions: bare soil, wood-chip mulch, and compost.
Cold hardiness was assessed using differential thermal analysis, monitoring bud acclimation weekly from early October and throughout the winter.
The analysis was based on LT50, the lethal temperature at which 50% of the buds subjected to cooling freeze.
The ability of buds to supercool was also used as an indicator of cold acclimation: the occurrence of low-temperature exotherms (LTEs) indicates the acquisition of the ability to avoid freezing through supercooling.
In both years, a progressive increase in cold hardiness was observed from autumn to early winter, but irrigation method resulted in differences.
Buds from drip-irrigated trees showed lower LT50 values than those from microsprinkler-irrigated trees, indicating a greater ability to withstand sub-zero temperatures.
The overall difference was approximately 1 °C and was statistically significant in both seasons. In 2021, an interaction between irrigation and soil amendments was also observed: under drip irrigation, buds in bare-soil treatments were less cold hardy than those associated with compost or mulch, whereas under microsprinklers, soil amendments did not affect LT50.
In 2022, by contrast, soil amendments had no significant effect on cold hardiness.
An interesting finding concerned the organic amendments themselves, since the greater late-season nutrient availability associated with compost and mulch could theoretically prolong vegetative activity and delay cold acclimation.
However, the data did not indicate such an effect: the number of acclimated buds in amended treatments was similar to or greater than that observed under bare soil, and in 2021 the drip + compost treatment showed the highest number of buds capable of producing LTEs by the first week of November.
With regard to soil moisture, drip irrigation maintained more stable water conditions than microsprinklers, with lower daily variability in soil water content, particularly in soils amended with compost and mulch.
This finding is noteworthy because, considering that lower tissue hydration is generally associated with greater frost resistance, greater acclimation might be expected under treatments characterized by lower water availability.
Instead, the researchers hypothesize that greater stability in soil moisture throughout the growing season may promote the development of cold hardiness, although they emphasize that the underlying mechanism remains unclear.
Overall, the study shows that drip irrigation may contribute not only to greater water-use efficiency but also to greater cold hardiness of sweet cherry buds, while the use of compost and mulch does not appear to delay autumn acclimation.
However, the results suggest that the relationships among water availability, plant nutrition, soil moisture dynamics, and frost tolerance are complex and require further investigation before these findings can be translated into specific agronomic strategies.
Source: Hannam, K. D., Houghton, E. A., Kuchta, S., Sharifi, M., & Forge, T. A. (2026). Drip irrigation and application of soil amendments can promote cold hardiness in sweet cherry (Prunus avium L.). Canadian Journal of Plant Science, 106, 1-5. https://doi.org/10.1139/cjps-2025-0242
Image credit: Stefano Lugli
Andrea Giovannini
PhD in Agricultural, Environmental and Food Science and Technology - Arboriculture and Fruitculture, University of Bologna, IT
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