by Todd Rutherford
As you are all probably aware, we live in a semi-arid climate in Colorado. Unless you have a landscape comprised entirely of native plants, you need to be cognizant of the occasional need for winter watering to maintain healthy landscape plants. This can be a challenge due to the fluctuating temperatures we experience. And unless you want to re-winterize your irrigation system each time you winter water, you likely will be watering by hand.
Generally speaking, if there has been no natural precipitation for a month and the temperatures have been above normal for your region, trees and shrubs planted within the last year will benefit from receiving supplemental 
water. Only water when the air and soil temperatures are greater than 40 degrees Fahrenheit, with no snow cover. Plants that are on the south or west side of your house are more likely to dry out before those on the east or north. And plants that get reflected heat from buildings, walls and fences or that are in windy sites are more likely to dry out more quickly.
Recently planted deciduous trees are most in danger from winter dry spells. Established trees are somewhat immune from winter drought, unless the dry spell is extreme. If you are uncertain if your tree is established, observe this advice from Colorado State University Extension Service: “Trees generally take one year to establish for each inch of trunk diameter. For example, a two inch diameter (caliper) tree takes a minimum of two years to establish under normal conditions.“ Water the newer and younger trees once a month with 10 gallons of water per each trunk diameter, measured at 6 to 12” above the ground. Let the water soak in slowly to a depth of 12”.
Similarly, recently planted shrubs are more susceptible to dry winter conditions than more established shrubs. For new shrubs, water them with 5 gallons, two times per month. Small established shrubs need 5 gallons once per month. Large established shrubs need about 18 gallons per month.
Newly planted evergreen trees and shrubs are also very sensitive to winter drought, because they don’t drop their leaves or needles so they still are transpiring moisture through the needles all year long. Some arborists recommend misting the leaves/needles with water rather than focusing on the soil. Some of the water will trickle down and get into the soil. Consider doing this 3 times a month for those new evergreens. This should help your evergreens avoid the brown damaged needles that occur during drought stress. Evergreens that need special attention during winter drought are spruce, fir, arborvitae, yew, Oregon grape-holly, boxwood, and Manhattan euonymus.
Obviously, if we receive enough precipitation, no supplemental watering is needed. The rule of thumb here is if snow still covers the ground or if there was a significant snow fall (6” or more) at least once in the last month, you probably don’t need to water that month. But if we have a dry spell and you’ve not properly watered your landscape plants, they may become weakened, making them prone to insects and disease.
If you have a recently planted lawn, consider giving it ½” of water per month during winter dry spells. Established lawns shouldn’t need supplemental watering because bluegrass goes dormant in winter.
Do not neglect to properly mulch all your trees, shrubs and perennials. This will help to keep your plants from further drying out.
Once you have watered your landscape plants, don’t forget to unhook your hose from the hose bib so as to avoid frost damage to the pipes once temperatures drop back down below freezing.
This is the official blog of Outdoor Design Group, Colorado Landscape Architects. For more information about our business and our services, click here.
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by Matt Corrion
Brrrrr… It’s cold out there! The last thing you are probably thinking about is landscaping. Or, if you are like me you already have the itch to get outdoors and are counting the days until spring. Whether you are a restless home gardener looking for reasons to get outside, or you are performing maintenance on a commercial property and want to do all you can to have it look great some spring, there are many tasks that can be accomplished over winter. Get the hot chocolate ready!
Key Dates
- Late February: Stop any pruning from this point on- spring is right around the corner, and woody plants are developing buds and preparing for the new season.
- Late March: Plants will begin to emerge for spring at this time. As plants (especially Xeriscape plants) emerge and show signs of new growth, begin to remove any heavy mulching that was done to protect them over the winter.
Trees and Shrubs
- Apply tree wrap to the trunks of young trees, early in the winter. This protects the bark from sun-scalding and damage from harsh winter winds.
- Watch for any heavy, wet snowfall. This can break off branches of trees and do a lot of damage. Shake heavy snow from trees and shrubs that are bending and showing stress. While this can be a threat throughout winter, trees are particularly vulnerable in early spring when buds and leaves are beginning to emerge, because this creates more surface for the wet snow to stick to.
- Hand-water your trees and shrubs if dry periods persist for a month or longer and the ground is not frozen. Keep in mind that areas facing the south and west will need water more than areas with northern exposure where snow will stay on the ground longer. Water in the middle of afternoon when temperatures are warmer (above 40 degrees Fahrenheit). You only do this about one time per month, and only if dry conditions persist.
- Make sure you have plenty of mulch around trees and shrubs- this helps maintain moisture and keeps the soil from drying out over the winter.
- Finish any pruning of trees and shrubs in January. When pruning trees, look to remove branches that appear likely to grow into each other or rub against other branches. When pruning shrubs, always try to maintain the natural size and growth habit of the species. Always use the right tool for the right cut.
Perennials and Ornamental Grasses
- Leave spent stems and seed heads on grasses and perennials until spring, to enjoy their winter beauty and to provide cover for birds and wildlife. If ornamental grasses and perennials have “flopped over” due to repeated snowfall, go ahead and cut them back now to achieve a neater look- otherwise, wait until early spring.
- Late in March begin to remove any heavy mulching that was done in the fall/winter to protect the plants and preserve moisture. We usually receive plenty of precipitation in March and April in the form of wet snow and rainfall. If there is too much mulch around the base of perennials and ornamental grasses (especially Xeriscape plants with low water-use requirements) then stem rot and root rot can occur if the mulch is too thick in the spring.
Lawns
- Minimizing traffic on lawns will help to keep from damaging the grass, especially if it has been a dry winter or the ground is frozen.
Winter Weather Considerations
- January and February are the driest months of the year (in terms of precipitation) for the Front Range of Colorado. Watch soil moisture closely, and hand water your plants if you receive little snowfall. In March, the level of precipitation generally picks up quite a bit.
Other
- If you are feeding birds, try to keep your feeders full as birds can become dependant on this source of food in winter.
- If it has been a dry winter, when you are plowing or shovelling snow strategically place snow around the base of trees and shrubs to provide added moisture.
- Start planning for design changes to your landscape for summer. Now is a good time to get your plans in order, and spring is the best time to establish new plants- so get ready early, because it will be here before you know it!
- Finally, sit back and wait for SPRING! A cozy fire and a warm drink will make the wait more bearable.
This is the official blog of Outdoor Design Group, Colorado Landscape Architects. For more information about our business and our services, click here.
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