Eye on Extension: Winter watering of lawns and trees is needed


VALLEY — This winter we have seen extremes in dry air, low snowfall, little soil moisture and fluctuating temperatures. These can be expected in the fall and winter, but this year it is drier than usual. The lack of snow cover can also allow damage to lawns, trees, shrubs, and perennial plants. Supplemental water will help save these plants.

All or part of a plant’s root system may die due to the lack of moisture. Affected plants may appear normal. They may start to grow in the spring using stored food resources. However, these same plants may be weakened and all or part of the plant may die off in late spring or summer as temperatures rise. Weakened plants may also be susceptible to disease or insect damage.

Lawns are prone to winter damage. Newly established lawns, whether seeded or sodded, are especially susceptible. If the lawn has a south or west exposure, it is more susceptible. Even established lawns will benefit from supplemental water during an extended dry period.

Woody plants with shallow root systems require supplemental watering during a dry period in the fall and winter. Woody plants that have mulch around the base will be in better shape than those without mulch as the mulch helps conserve moisture. 

Flowering or herbaceous perennials and ground covers in exposed sites also benefit from added winter moisture in a winter like we have now. If there are open cracks in the soil, there is added exposure of roots to cold and drying weather. Winter watering combined with mulching can help prevent damage.

Apply supplemental winter water when the temperatures are above 40 degrees Fahrenheit. Apply the water during the middle of the day. This will allow the water time to soak into the soil before the nighttime freezing. A solid layer of ice on a lawn can cause suffocation or matting of the grass. The layer of ice would need to be there for about a month or more.

Plants that are near building or other structure may get added heat from the reflection of the structure. The low angle of the sun makes this more prevalent.  Windy sites also dry out faster. Lawns in warm exposure areas are more prone to late winter damage. 

Watch the weather conditions and water when there is an extended period of dry weather without snow cover. Water one or two times per month during these times. 

New planted trees are most susceptible to winter drought injury. Trees generally take one year, per inch of trunk diameter, to become established. During establishment additional water will help the trees. Allow the water to soak into the soil at least 12 inches. 

Trees can be watered by sprinklers, deep-root fork or needles, soaker hoses or soft spray wands. Apply water near the drip line of the trees. Also apply the water in many locations around the drip, or beyond, the line of the tree. If using the fork or needles, don’t insert the fork or needle more than 8 inches into the soil. 

As a rule of thumb, apply 10 gallons of water for each inch of the trees diameter. Use a ruler to measure the trees diameter about 6 inches above ground level.

Newly planted shrubs require more water than established plants for at least one year. As a rule of thumb, during winter, October thru March, apply 5 gallons of water twice a month. Smaller plants can be watered once a month. Very large shrubs can use 18 gallons of water per month. If there is rain or snow, the supplemental water can be reduced by the amount of rain or snow.

Herbaceous perennials will vary as bare root plants take longer to establish than container grown plants. Fall planted plants are slower to establish than spring plantings. Winter watering is recommended for fall planted plants, bare root plants or those that are in windy or southwest exposure sites.

If you have questions, you can also call the Colorado State University Extension, San Luis Valley Area Office at 719-852-7381, or email us at marvin.reynolds@colostate.edu.  Check out our website at http://sanluisvalley.colostate.edu

Extension programs are available to all without discrimination, Colorado State University Extension, U.S. Department of Agriculture and Colorado counties cooperating.