Winter is a time of dormancy for all plants, which makes for an opportune time for a few maintenance practices on trees and shrubs.

Mulching

Putting a three to five inch layer of mulch down in late fall or early winter has several benefits to your trees and plants. Mulch provides a protective layer for newly established tree roots while providing nutrients and creating a quality soil texture as it decomposes (promoting beneficial microorganisms).

Mulch can be as simple as wood chips provided from public resources/entities or more refined tree bark and wood chips purchased at your local landscape outlet. A thick layer of mulch will begin to breakdown with the addition of water and temperatures above freezing. The breakdown of this natural material adds essential macronutrients and micronutrients. These nutrients help regulate soil pH, aid in root and crown growth, and promote healthy vascular systems within plants.

Be sure to place mulch near the base of a tree, but not against it. 

Structure Pruning

When the temperature begins to drop below freezing, trees go dormant. All activity within the canopy of the tree stops, making this an excellent time to evaluate your tree for structural problems. Broken branches, crossing branches and dead branches can be removed easily in the winter with little or no detriment to the plant. Removing branches during dormancy reduces the chance of disease or infection, reduces shock/stress on the tree during its growth and storage phases, and reduces the risk of removing beneficial branches (it’s easier to see the structure of deciduous trees when leaves are gone). Coniferous trees pruned during dormancy have a smaller chance of being attacked by predatory insects (such as Tussock moth, and various Ips and Pine Bark Beetle species) during flight season. Starting a structure pruning regiment on young trees ensures a healthier, more easily maintained tree as it matures.

Transplanting

Transplanting can be done year round if the proper measures are taken. Transplanting a tree in the late fall or winter is easier on the plant and is less worrisome for the homeowner. Transplanting in the fall and winter requires less water, and decreases shock and chance of root ball failure.

Reasons for transplant include proximity to a structure or other trees; when the current planting situation poses a hazard, such as thorns, poisonous fruit or allergies; tree is aesthetically more pleasing in a different area; or poor species performance in current planting situation.

When transplanting trees it is necessary to dig a properly sized root ball. The ratio is 2:1 or 3:1 depending on the age and species of the tree. For example, if you have a three inch caliper tree, you would dig a six to nine foot wide root ball. As you can see, the sooner you can transplant your tree or shrub, the easier it will be on you and the tree. The older the tree is the more stress it will endure after transplant, even in the winter.

Winter months provide colder temperatures that help keep the root ball intact during transport. Transport for smaller trees can be accomplished with large buckets or wheelbarrows, while larger trees require ball carts or extra helpers. The plant’s new home should have a nice wide planting hole to allow space for roots to establish and should be saucer shaped, not square. Loosening the sides of the new planting hole also aids in root penetration/establishment.

Watering

During dry winters, occasional watering will help trees remain in top health. According to the Colorado State Forest Service, an extended winter dry period is one with more than two weeks without lasting snow cover.

The best time for winter watering is on warmer days with temperatures above 40 degrees. Hand water the entire area underneath the full span of the tree's branches. To ensure deep penetration, use a drip or soaker hose on a low setting to apply water slowly to the full area at a rate of 10 gallons per inch of tree diameter. 

Protecting

Thin-barked trees like honeylocust, maple and linden are susceptible to sunscald and frost cracks because of drastic winter temperature fluctuations. To prevent bark damage, wrap the trunks of younger trees up to the first branches using commercial tree wrap. Leave the wrap on until early April.