Just like any other season when precipitation is sufficient, whether it’s in the form of rain, snow or ice, dormant warm season grasses will continue root growth and water and nutrient uptake although at a reduced rate caused by slowed metabolic activity. Cool season lawns and winter plantings of annuals to provide color have to have sufficient levels of moisture because they are actively growing. How do we accommodate these needs while preventing problems such as winterkill in turf or dead pansies due to lack of water?
Drought conditions: It is not uncommon to have long stretches of time between rain events during the winter months. After several weeks have passed without rain, applying water once a week will be enough to keep your sod hydrated until natural precipitation occurs. If using an irrigation system be sure the watering cycle starts later in the day to prevent dangerous ice buildup on hard surfaces such as roads and walkways.
Extreme cold fronts: During the winter months it is not uncommon to have cold, dry, and windy fronts move through. This, accompanied by rapid temperature drops during the day (or night) will cause the bark layer of shrubs and trees to split in effect girdling the plant. The same thing happens to the dormant turf. The soil will give up its moisture quickly in these conditions causing the grass to become “freeze dried.” The water that is in the grass plant at the cellular level freezes and expands destroying the tissues. This causes winterkill which shows up as what looks like large burned patches in the lawn during spring green up. Paying close attention to weather reports and irrigating before the arrival of the front, may help prevent or decrease the amount of winterkill observed later.
Plants that provide color: Annuals planted to provide color in the landscape this time of year are actively growing and require moisture. Isolating these areas of color with drip irrigation will apply water as needed for growing healthy plants while preventing over watering nearby dormant turf.