Research updates from 2025 Christmas tree irrigation experiments
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EmailThe MSU Extension Christmas tree team shares results on tree growth under different irrigation scheduling treatments.
Irrigation in Christmas tree production can improve tree growth and survival (Photo 1). This is especially true for recently established fields during periods of drought (Photo 2). In a recent survey, 32% of Michigan Christmas tree growers indicated they plan to start or expand their current irrigation system. However, determining when and how much irrigation water is needed can be difficult to pinpoint.
The amount of irrigation can vary due to a host of factors including the water holding capacity of the soil, the trees growth stage, and weather conditions. Applying too much water may result in soil erosion, promotion of root rot diseases, leaching of nutrients from root zone, and waste both water and energy needed to power pumps. In contrast, insufficient irrigation may not provide adequate water to the soil and may result in decreased growth and tree survival.
To assist growers in developing guidelines for irrigation management, the Michigan State University Extension Christmas tree team installed irrigation trials on two cooperating Christmas tree farms, one in Allegan County and one in Wexford County. Treatments included non-irrigated control, grower’s standard irrigation and evapotranspiration (ET)-based irrigation.
Results from 2024–2025 showed that ET-based irrigation increased cumulative leader growth by 10–30% compared to both the grower’s standard practice (e.g., rule of thumb, 1-inch per week) and non-irrigated treatments (Photo 3). These results indicate that ET-based irrigation more effectively maintained optimal soil moisture throughout the growing season.
Practical tools for implementing irrigation scheduling are available in the Irrigation Scheduling Tools fact sheet from Michigan State University (MSU) Extension. In addition, in-field soil moisture monitoring using sensors is recommended, as it tracks soil moisture dynamics within the root zone, enhances understanding of crop water use, and helps prevent over- and under-irrigation.
Information on using soil moisture sensors for irrigation management can be found in MSU Extension Bulletin E3445: Improving Irrigation Water Use Efficiency: Using Soil Moisture Sensors.
For further questions on implementing this model, please contact Bill Lindberg at lindbe35@msu.edu.
This project is supported by North Central Region Sustainable Agriculture Research and Education (NCR-SARE) Partnership Grant and Michigan Department of Agriculture and Rural Development (MDARD) Horticulture Fund. Support from the Michigan Christmas Tree Association and grower collaborators (Dutchman Tree Farms, Korsons Tree Farm, Badger Evergreen, Top Hill Farm) also made this research possible.
