Maintaining the Winter Landscape – By Tyler Mason
Wyoming’s difficult winters challenge perennial gardens and gardeners alike. The winter sun and strong winds dry out the soil. This combined with the least amount of snow cover on the front-range leaves plant roots perpetually thirsty. Sudden fluctuations in temperature don’t help perennial trees and shrubs either. However, taking some preventative measures and supplemental winter watering make tree maturation possible.
Protecting your perennials
Selecting zone hardy plants is the most important step in helping perennials overwinter. Be sure to look on the back of plant tags at your nursery or garden center for Zone 4 hardiness or lower. Zone 5 plants can sometimes be marginal in Cheyenne’s climate due to strong winds and low levels of precipitation. Warm sunny days and cold clear nights play havoc on a plant’s ability to moderate internal temperatures. Therefore, regulating temperature changes with insulation is essential.
Hardy, non-grafted shrub roses are the easiest to overwinter and have a better chance at survival if they go completely dormant early. Stop fertilizing after August 15 and stop dead-heading (or removing spent flowers) after August 25th. This will help the plant form rose hips which help a plant overwinter more easily. Roses also benefit from staying uniformly cold all winter. Placing a 10-12” layer of mulch around the core of the plant helps moderate temperature fluctuations and conserves soil moisture. Fallen pine needles work wonderfully! Wait until night temperatures are in the low 20s for a few nights before mounding the roses with mulch. Also remove any fallen leaves, prior to mulching, as they might harbor disease which could be detrimental next year.
Preventing sunscald injury
Sunscald injury comes in the form of discolored bark, sunken areas, and bark splitting which leaves dead tissue inside the affected area. This wound creates stress for the tree or can lead to insect and disease infestations. It is a common problem with young trees with darker colored bark and/or trees with thin bark layers. Sunscald injury occurs, generally on the south side of the trunk, when there are sudden day and nighttime temperature extremes. The sun heats the south side of the trunk, encouraging cells to expand, while the north side of the trunk stays cool. When the sun sets, the bark on the south side suddenly contracts leading to bark splitting. Splitting of bark can be exacerbated by dry soils. Be sure to winter water your trees if we go many weeks without moisture or snowcover.
Fortunately, preventing this injury is easy and affordable. Placing tree wrap around the trunk and lower limbs reflects the sunlight away from the bark surface and moderates the temperature fluctuation. There are crape paper-like wrap and white plastic tree wrap. If using paper-based wraps, start at the bottom of the tree and wrap upwards. Place the wraps on the tree in the fall when night temperatures dip below freezing. Remove the wraps the following spring after the last frost.
Mulching vegetable gardens in winter has also been shown to be beneficial to the fertility of the soil and increases next year’s yields.
Trees, shrubs, and grass endure winters in Cheyenne with dry air, little precipitation, and temperature extremes. It can be devastating to the root zone to not receive adequate moisture during winter. Mulching is one way to conserve soil moisture and moderate temperatures. A 2-3” layer of mulch placed 4-5’ around the tree works great. Don’t apply the mulch within 6” or so of the base of the tree as mice make make a home in your mulch and feed on the tree bark.
Winter watering is straightforward process. On days that reach 40 degrees F or warmer water mid-day. Be sure to turn the water off so the moisture has time to be absorbed instead of turning into ice. As a rule, try to provide 10 gallons of water, at each watering, for each diameter inch of trunk. Watering within the dripline is advisable. Don’t forget about watering newly planted shrubs too!