By Jeff Floyd
Certified horticulturist and arborist
One does not need to search long to spot over spraying irrigation water as it freezes on streets during the coldest days of winter. This site can be frustrating especially considering plants do not require much water this time of year. In fact, watering the landscape as little as once per month during winter is often all that is necessary to ensure plants make a nice recovery in the spring.
How much water do plants need? During the hottest months of the year, one inch to one- and one-half inches of water weekly is usually recommended. A properly designed residential irrigation system can easily deliver this amount over the course of two cycles in a week. Landscape plants have a much lower irrigation demand during winter since they are at rest and not as readily losing water from the soil around their roots.
Trees and grass have competing interests. Warm season turfgrasses benefit from an irrigation cycle at least once per month during winter. Although, grasses such as Bermuda and St. Augustine are perennials, they often lose up to half of their root system before coming out of dormancy. They may have even greater root losses during dry winters. Trees and shrubs have large root systems and an ability to explore more of the soil for water. Watering woody plants too frequently during winter is more likely to harm them than benefit them.
Established trees and shrubs can often tolerate more than four weeks or longer without supplemental irrigation during fall and winter. Many horticulturists believe excess water in the cells of certain woody species was one element which contributed to plant losses during the February polar vortex of 2021. Many experts believe the water expanded as it froze within trees and destroyed a lot of healthy wood. It can be difficult to find a balance between adequate irrigation for turf while not overwatering trees.
Keep in mind that we are talking about the application of supplemental irrigation. During any month we receive rain, we can reduce our landscape irrigation needs proportionately. In other words, if we get an inch of rain on a given day during December, say December 25th, then supplemental irrigation may not be necessary during the following four weeks or until around January 22nd.
Take it easy on the irrigation this winter. Your plants, your neighbors and your pocketbook will all appreciate you for it.
