Winter Tree Services
Ross Tree, a local Denver tree company, operates twelve months of the year and provides winter tree services throughout the Denver area. The most popular winter tree services are deep root watering, winter pruning, and dormant oil spraying. Denver is experiencing its second winter drought, so trees need deep root watering to get them through winter dry spells. Since trees set their buds in late summer, winter is a great time to prepare trees to withstand Denver’s winter storms. Spraying dormant oils controls overwintering tree insects such as aphids, mites, and scales.
We Live In an Arid Climate
By this time of year, Denverites have already blown out their sprinkler systems and raked up their leaves. They forget about the severe winter drought that Denver experience last year, and it looks like we are heading into another dry spell this year. October was dry, and the 30-day forecast for November shows mostly sunny days with no snow predicted. Some believe snow will provide enough moisture to sustain their trees until spring. However, there is little or no snow cover to provide soil moisture at this time.
Dry winters are the norm since Denver has a semi-arid, continental type of climate. Denver’s average amount of annual precipitation is 13.4 inches. Native grasses grow fine in these conditions, but not trees. Birches, Maples, Lindens, Alders, and Ash trees have shallow root systems and require supplemental watering during the fall and winter. Evergreen trees also benefit from watering. As the chart above shows, Denver is about 40 percent below its average annual precipitation in 2020, so it is time to think about deep root watering and fertilization of trees, and the sooner, the better.
According to Denver’s City Forester, trees need 10 – 20 gallons of water per week for every inch of diameter. For example, a 2-inch diameter tree requires 20 – 40 gallons of water in one week, while a 20-inch diameter tree needs 200 – 400 gallons of water in a week. That is a lot of water. Most homeowners do not have the time or equipment for large deep root watering jobs. For proper tree watering, it is time to call a professional tree company, like Ross Tree.
Drought injures the root systems of trees. Affected plants may appear perfectly normal and may resume growth in the spring. Or they die back with dead branches or do not leaf-out in the spring. Trees weakened by drought become susceptible to insect and disease problems.
Below are signs of tree distress caused by drought:
- Trees turn colors and shed leaves prematurely.
- Shoot growth appears at the bottom of a trunk.
- Winter kill appears throughout the crown of the tree.
To get the best results, the Ross Tree crews use a deep-root fork or needle and forcing water down to a depth of 12 inches. Below are the wintering watering guidelines provides by the Colorado State Forest Service.
- Water slowly: Deep root watering allows deep soil penetration and is cost-efficient.
- Lawn trees: Trees located in irrigated lawns generally do not require additional water in the summer. After the system is shut down, we recommend supplemental watering during extended dry winter periods.
- Mulch: Mulch reduces tree stress by retaining soil moisture and saving water. Apply 4 inches of mulch onto bare soil within 2 to 3 feet from the trunk base. Make sure the mulch does not touch the tree trunk.
- Winter Watering: Water only during the day and when air temperatures are above 40 degrees F, allowing time for the water to soak into the soil.
- Newly planted trees and shrubs: They require more water than established plants and should be watered twice per month between October – March.
- Water a wide area: Tree root systems spread two to three times wider than the tree’s height. The most absorbing roots are in the top foot of soil. Soak the entire area within the drip line.
Chapstick for Trees
Colorado is known for its 300 days of sun. Desiccation is an injury caused when the loss of moisture by the tree leaves exceeds the water taken in by its roots. Evergreens and some shrubs in Denver are especially susceptible to windburn and sun-scald. Ross Tree applies wax-like anti-transpirants to prevent plants from losing moisture through their foliage and help them look their best throughout the year. It is like chapstick for plants.
Deep Root Tree Fertilization
In the forest, the ground is littered with leaves and decaying matter where trees take up nutrients easily. In yards, trees compete for nutrients with turf and shrubs. Also, some trees grow poorly in Denver’s clays soils because of lack of aeration, which decreases the root systems’ ability to replenish water loss brought about by our dry climate. Ross Tree recommends deep root fertilization three times a year to give trees need extra nutrients to reach their full potential and offset the lack of natural nutrient recycling in a manicured setting. Below are signs that trees need fertilization:
- Stunted growth: Clay soils stunt tree growth, and fertilization reverses this condition.
- Leave discoloration: Discoloration is a sign that your trees are not getting enough nutrition. Maples and some Oaks are prone to Chlorosis. Affected trees cannot take up iron from the soil, so their leaves turn yellow.
- Newly planted: Freshly planted trees are low on nutrients and need fertilization to keep them growing.
Ross Tree uses Essential Plus for deep root fertilization. It is a 100% natural soil amendment derived from potassium hydroxide, organic proteins, sugars, and Humic acid. Humic acid replenishes soils depleted of organic matter, helps alleviate soil compaction, and provides a food source for beneficial soil microorganisms. The deep root injection:
- Enhances beneficial microbe populations
- Provides microbes with a necessary food source
- Improves root growth
- Allows oxygen to penetrate the root zone and encourages fibrous roots to colonize
Winter Tree Pruning
It is ok to prune trees in the winter because trees bud in late summer to prepare for the next growing season. Also, pruning in the winter does not stimulate additional growth. The benefits of winter tree pruning are as follows:
- Easier to evaluate tree structure: After the leaves drop, it is easier to see your trees’ structure and identify any problems. Winter pruning truly benefits younger trees and sets them up for a successful growing season.
- Better looking trees in spring: After a winter pruning, the tree directs energy to fewer branches, which improves the overall vigor of a tree. The buds on the remaining branches produce healthier leaves, fruit, and limbs.
- Saves money: Frozen ground allows heavy equipment to be staged next to the tree, so the job goes faster, lowering job costs and producing better outcomes.
- Less tree stress: Research shows that pruning during dormancy and before buds break in spring leads to faster wound closure and less stress. Healed wounds keep out destructive insects and pathogens.
- Avoids spreading disease: Many common trees diseases are inactive in the winter, so cold days are a perfect time to prune out dead wood, cankers, and other parts of the affected trees.
- Prevents winter storm damage: Winter pruning takes out any branches most likely to break to make trees less susceptible to snow breakage.
Cold Weather Damage to Trees
When temperatures drop slowly, the tree has time to harden and acclimate to the freezing temperatures. The sap flows into the root system, and the tree adds tissue to toughen up and protect its branches and trunks as winter approaches. However, over the last two years, Denver experienced sudden drops in temperature in October. During a warm day, the tree cells beneath the bark become active. At sundown, the temperature suddenly drops, and the cells did not have the time to return to dormancy and freeze, injuring the tree. Below are the types of freeze damage:
- Winter kill: Symptoms of “winter kill” include brown or black discoloration or branches and leave limpness. Pruning in the winter takes care of any damage caused by polar plunges in the fall.
- Sunscald: Sunscald affects tree trunks and large branches. Over time, the bark of the tree breaks down, exposing the tree to the elements.
Ross Tree uses light-colored wraps for winter protection. We wrap the tree in an overlapping fashion from the ground to the first branch. Homeowners should remove the wrapping after the last frost in the spring to avoid mold formation.
Dormant Oil Treatment
Dormant oils are sprayed in the winter to control tree insects such as aphids, mites, and scales common to the Denver area. The oil suffocates the eggs, larvae, pupae or adult stages of insects overwintering in trees. Dormant oils are environmentally safe since they dissipate quickly by evaporation, leaving little residue or toxicity.