Colorado gardeners hear the phrase “Don’t forget to winter water” every year, but the real reason it matters often gets lost. Winter watering isn’t about pampering plants — it’s about protecting the shallow, vulnerable root systems that keep your landscape alive.
Without supplemental watering, trees, shrubs, roses, perennials, and lawns will suffer damage. This is especially true as we experience extended dry spells.
In Colorado, an “extended dry spell” in winter typically means three or more weeks without measurable precipitation or snow cover. Little or no snow cover — even if it snowed recently, most has melted quickly or blown away, leaving dry, exposed soil — especially on south- and west-facing slopes or near buildings.
The answer is to provide supplemental water. That said, for winter watering to be effective, there are key factors you need to consider, including temperature, time of day, and sprinkler type. First, pick a day when the ambient temperature is forty degrees or higher and there is no snow on the ground. Plan to water around midday, to allow time for the water to soak into the ground. You can water using a soft spray attachment such as an adjustable water nozzle or attach a simple sprinkler to your hose. Don’t turn your sprinkler system on.
Water when the ground isn’t frozen. You don’t need special tools to tell whether soil is frozen. Take a long screwdriver and push it into the ground. If it slides in easily, the soil is not frozen. If it stops abruptly or only goes in an inch or two, the soil is frozen. This works even in heavy clay.
If daytime temps have been above 40°F for several hours, the top few inches often thaw enough to accept water. If it’s been freezing for days, assume the soil is frozen.
When you do water, aim for slow, even moisture applications, using a hose-end sprayer, sprinkler, bubbler, or shallow root-watering needle. Avoid turning on your sprinkler system.
Pay particular attention to south- and west-facing exposures where soil dries fastest. Plan to water once every 4–6 weeks during dry spells.
Trees: Check the thickness of the tree trunk when trying to figure out how much water to apply. A general rule of thumb is 10 gallons of water for every inch of trunk diameter. A 3-inch diameter tree should receive 30 gallons of water.
If you’re unsure how long to run your sprinkler or hose end sprayer, start by calculating the flow rate coming from your hose bib. An easy way to do this is to use a 10gallon bucket. Turn on the hose at the pressure you’ll use and time how long it takes to fill the bucket. If it takes 5 minutes to fill a 10-gallon bucket, the gallons per minute (GPM) coming from your hose bib equals 2. (10/5 = 2 GPM). To achieve the 30 gallons needed for a three-inch tree, you will need to run the sprinkler or hose-end sprayer for 15 minutes. (30/2 = 15).
Don’t water directly against the base of the trunk – rather you should water along the ‘dripline’. This is the area located under the outer circumference of the tree branches. Move the sprinkler every few minutes to cover the entire dripline.
Once you know the GPM, you can apply the same timing requirements for the rest of your landscape plants, including:
Shrubs: For newly planted shrubs, apply 4-5 gallons of water. For small established shrubs that are less than 3 feet tall, 5 gallons of water every 4 to 6 weeks. For established shrubs over 6 feet, 18 gallons per month.
Roses: Established roses need 4-5 gallons per plant per watering, applied slowly at the base of the bush. Newly planted roses (1st–2nd year) 4-6 gallons per plant, because their root systems are smaller and dry out faster. Water twice as often as established roses (every 2 weeks).
Large shrub roses and climbing roses need approximately 6-7 gallons, depending on canopy size and exposure. These have more aboveground masses that lose moisture even in dormancy.
Perennials: Established perennials about ½–1 gallon per plant. Larger clumps (peonies, daylilies, ornamental grasses) may take 1–2 gallons. Newly planted perennials (first year) need 1–2 gallons per plant. Their young root systems dry out quickly in freeze–thaw cycles.
This includes any perennials you are trying to winter over in containers.
Turf: If it’s been three or more weeks without measurable precipitation or snow cover, cool season grasses need to be watered. This includes Bluegrass, Perennial Rye, and Fescue. Plan to provide 1-2 inches of supplemental watering every four to six weeks. This will hydrate the roots and help control winter mites, which can infest and kill drought-stressed turf especially on exposed slopes and south or west-facing areas during winter and early spring.
Newly planted trees, shrubs, roses, and perennials are the most vulnerable to winter drought because their root systems are still tiny, shallow, and not yet connected to the surrounding soil. A new plant has only its root ball and a few exploratory roots. It hasn’t grown the wide, shallow network that established plants depend on for moisture.
New plants can only access the water that’s right around the root ball — and that dries out fast in Colorado winters. In addition, mature plants have carbohydrates and moisture reserves in their tissues. New plants don’t have that buffer yet.
Transplant stress compounds winter stress. Those newly planted trees, shrubs, perennials, and roses are struggling to recover from root loss during planting. Add winter drought, and the risk of dieback skyrockets.
The point of all of this is to protect your investment with supplemental watering throughout the winter and spring months.
When you are done watering, disconnect the hose from the bib and store it.
