Unlike some parts of the country, Colorado can experience periods of especially harsh fall and winter conditions characterized by dry air, low precipitation, little soil moisture, and fluctuating temperatures. When we experience extended dry periods, there is not enough soil moisture which puts the root system of trees, shrubs, perennials and lawns at risk if not given supplemental water. Plants that are affected may appear normal in the spring but die when temperatures rise in the late spring or summer because their resources have been depleted. Lack of winter water may also make plants susceptible to insect and disease problems.
WHEN TO WATER?
Monitor soil conditions closely from November through March and water during dry periods when there has been no snow cover for two weeks. You need to water when air and soil temperatures are above 40 degrees F, the soil is not frozen and there is no snow on the ground. You should also water mid-day so the water can soak into the ground before freezing nighttime temperatures occur. Don’t forget to disconnect the hose when you are finished watering.
WHAT TO WATER?
Newly planted trees or plants, transplanted plants, evergreens and broadleaf evergreens that loose moisture through their needles/leaves, and shallow rooted trees are especially vulnerable. Lawns, especially newly established ones, can also suffer winter damage and will need occasional supplemental watering to avoid susceptibility to winter grass mites and desiccation. Even established plants should be watered in times of winter drought but can go longer between watering than the categories mentioned above.
HOW MUCH TO WATER?
Most trees, especially when they are establishing their root systems during the first five years after planting, should get ten gallons per inch of trunk diameter. Smaller shrubs (under 3’ tall) should receive five gallons and larger shrubs (over 6’ tall) should receive 18 gallons of water.
WHERE TO WATER?
Water trees to a depth of 12” using a deep root watering device and apply water to all areas beneath the tree and its dripline. Shrubs should also be watered around the base and within the dripline. For newly planted perennials, check the soil conditions 2-3” deep and water around the root ball if the ground appears dry.
WHAT ELSE TO DO?
Winter mulching is another helpful practice to combine with watering. Plants in exposed areas, generally warmer south and west exposures, are subject to freeze-thaw conditions which open cracks in the soil that expose roots to cold and drying.
SOURCES: Colorado State Extension Fact Sheet 7.211 – Fall & Winter Watering http://www.ext.colostate.edu/pubs/Garden/07211.html
Planttalk Colorado™ – Script 1706 – Winter Watering http://www.ext.colostate.edu/ptlk/1706.html