Despite light snows, the grim truth is that the landscape is thirsty. Though our mountains are snowcapped, lower elevations are dry, and landscapes are getting parched.
Winter watering is one of the best ways to keep trees, shrubs, lawns and perennials healthy throughout the year. Without it, soils dry and tender feeder roots, which are responsible for taking up water and nutrients, shrivel and die.
In spring, plants use stored reserves to grow, pouring their strength into healthy leaves, stems, trunks or flowers. But damaged root systems leave them vulnerable when heat sets in, and these plants struggle with scorch, twig dieback, poor leaf size, or disease and insect attacks.
Water once or twice per month through March if we don’t have much snow or rain; in general landscapes need an inch of water per month in winter. Measure snowfall with a ruler, then write down each storm’s accumulation. Add it up every four weeks. Less than 12 inches total means it’s time to water.
Drag out hoses when temperatures are above 40 and there’s no snow cover. Water slowly so it sinks into the frozen ground. I use a timer to shut off the water, and set a timer in the house to remind me to move the hose or disconnect it from the house before evening.
If you divide winter watering over several days, pay attention to plants closest to south or west facing walls or fences first; the reflected heat intensifies their plight. Windy places with water wicking from the ground should be second on your list, which in Colorado, means everything east of the divide.
Water around the dripline of trees and shrubs – the area that falls under the outer tips of the branches, soaking the ground two to three feet on either side of the dripline. Give your trees 10 gallons of water per diameter inch of trunk every month.
Shrubs are trickier: new shrubs—those planted less than one year ago—need five gallons twice monthly. Once they’ve been in the ground for over a year, reduce water to five gallons once per month for small, three-foot tall shrubs and 18 gallons once per month for those over six feet tall.
Lawns, too, need a drink. Established lawns will benefit from watering, but the critical ones that need moisture are the new ones. If it was sodded in after early September, it’d be good to water it.
If you’ve had lawn mite problems in the past, it’s time to water. Dry January and February months are when mite populations start to rise. Though mites haven’t yet started to damage the lawn, their potential to do so increases with their numbers, which can be held at bay by moisture.
To water a lawn in winter, warm days with temperatures above 45 degrees is a must. Then drag out your hose with a sprinkler, or set the water to a slow trickle. The good news right now is that the soil isn’t frozen so we won’t have water ponding on the lawn. Standing water is the worst thing for lawns, especially if it is forming a layer of ice on it; that harms the turf.
Water fall-planted perennials and perennials located in windy or southwest exposures. But the key to perennials is ensuring they have a thick, four- to six-inch covering of mulch to prevent freezing and thawing of the ground. For more information, see the Fall and Winter Watering fact sheet at ext.colostate.edu/pubs/garden/07211.html.
Colorado State University Extension, together with Boulder County Parks and Open Space, provides unbiased, research-based information about consumer and family issues, horticulture, natural resources, agriculture and 4-H youth development. For more information contact Colorado State University Extension at the Boulder County Fairgrounds, 9595 Nelson Rd., Box B, Longmont, 303.678.6238, e-mail firstname.lastname@example.org or visit ext.colostate.edu/boulder.