As we are ending 2023, the temperature high and/or low could be consistently at or less than 32°F with a possible chance of snow precipitation. For turfgrass areas in December, the process of dormancy for both warm and cool-season grasses has already occurred. In regards to water use in dormant lawns in cooler temperatures, December is not the time to use irrigation in grass areas. The Photo above is from Pioneer Underground Lawn Sprinklers. https://pioneerunderground.net/sprinkler-winterization-omaha/

As we look back at the last five years (shown in Table 1), the high-temperature averages in the majority of Nebraska were above freezing in December at Lincoln, Omaha, Scottsbluff, and North Platte, based on data from Nebraska Mesonet. But when it came to the low temperatures in Table 2, they were far below the freezing point compared to the day-time temperatures.

Table 1. Maximum Temperatures Average (in Fahrenheit) December 2018-2022

Table 2. Minimum Temperatures Average (in Fahrenheit) December 2018-2022

Based on the data from the past in Nebraska, the temperatures lead to continuing dormancy in turfgrass areas in December.

But why is it important to turn off the irrigation?

• Higher risk of irrigation system problems. It is unsafe for the irrigation system to run in temperatures of less than 32°F. This can lead to severe problems with irrigation not working in the spring.
• Grass in dormancy. Dormancy is when the turfgrass plant does not die but it preserves the added nutrients and moisture for winter storage before the decrease in temperatures. Disturbing the grass with irrigation is unnecessary and dangerous in freezing temperatures. Unnecessary irrigation can lead to problems with grass growth in the spring. Keep in mind watering can be done in dormant grass in the summer, but not in the winter.
• Not necessary for irrigation in December. With limitations to the use of irrigation for watering, it is not needed to apply unnecessary water when the grass is not growing in cooler temperatures at less than 32°F.

With the above reasons to turn off irrigation, there are proactive options that can be taken to lessen the damage of irrigation.

Options to turn off irrigation

All these options listed should be considered and completed by December or when temperatures are about to reach freezing temperatures of less than 32°F:

• Turn off the main irrigation control. There is a chance the programs could turn on during the winter months. Even if the program is only set to turn on in the spring, it lessens the stress that the irrigation could turn on unexpectedly.
• Cover outdoor faucet. If you have an outdoor faucet at your home, cover it for further damage in cooler temperatures. This can be done by putting in a bucket or a specialized outdoor faucet cover. When there is expected snow or ice that can occur in the winter, there is no further damage in the output when protected by these structures.
• Draining the hose. The reason for this approach is to protect the hose if water is still in it which can freeze and damage the hose. If it is not drained and used in the spring, this can damage the hose and the outdoor faucet. Timing to remove water from the hose should occur when the first frost happens in the late fall.
• Irrigation blowout. Also known as “winterization”, it’s the action of applying high-pressure air via a compressor into the irrigation piping for water removal in the irrigation system. This should be done by a professional. Even with this approach, some water can be retained underground due to the soil and age of the irrigation system.

Following the proactive steps of not using irrigation during colder temperatures in winter months like December is important. If water is still in use after dormancy, there is a high risk of grass and irrigation system damage.

Have a Happy Holidays and enjoy the rest of 2023.