4 Tree Care Trends Homeowners in Centennial, CO Cannot Ignore in 2026

Emerald Ash Borer, or EAB, is present in Centennial, so homeowners with ash trees should not wait for severe canopy loss before asking for help. The insect’s larvae feed beneath the bark and disrupt the movement of water and nutrients, eventually killing the tree.

The City of Centennial’s Emerald Ash Borer guidance says EAB was confirmed on the west side of Centennial in June 2024. The City estimates that an infested ash tree may die within 3 to 5 years. Colorado State University Extension’s EAB resource notes that death may occur within 2 to 4 years after symptoms first appear.

The threat is significant because ash trees make up about 15% of Colorado’s urban forest, and the Denver metro area has an estimated 1.45 million ash trees, according to CSU Extension.

Watch for:

• Thinning near the top of the canopy
• D-shaped exit holes in the bark
• Vertical bark splits
• S-shaped galleries beneath loose bark
• New shoots growing from the lower trunk
• Increased woodpecker activity
• Progressive branch dieback

Other problems can cause similar symptoms, so a visual check may not confirm EAB. A professional evaluation can help determine whether treatment, monitoring, or tree removal is the right next step.



Healthy or lightly affected ash trees may be treatment candidates. Severely declining trees may need removal before the wood becomes brittle and more difficult to handle safely.

The 2026 Centennial Tree Program is complete. The City of Centennial Tree Program page directs residents to check back in early February for 2027 information.

Under the 2026 program, residents could purchase one qualifying tree for $85 plus tax while supplies lasted. Homeowners who had removed an ash tree within the previous year could receive a refund for the full cost of a qualifying program tree after submitting documentation.

Program rules, prices, tree species, and refund requirements may change. Keep removal records and verify the current details before purchasing a replacement tree.

Late winter is one of the best times to prune most deciduous trees in Centennial. Without leaves blocking the view, an arborist can see weak attachments, crossing limbs, deadwood, and overextended branches more clearly.

The Colorado State Forest Service’s pruning guidance explains that late-winter pruning makes structural problems easier to identify and allows cuts to begin closing as spring growth starts. This timing can also help prepare trees for the wet, heavy snow that often arrives along the Front Range in late winter and spring.

During local trimming visits, we often find that the most urgent problems are not the largest branches. They are cracked unions, dead limbs over driveways, or smaller branches rubbing against roofs and siding.

Professional pruning may include:

• Removing dead or broken branches
• Correcting crossing or rubbing limbs
• Reducing the weight on an overextended branch
• Improving young-tree structure
• Providing clearance from a roof or walkway
• Addressing competing leaders or weak attachments

Learn more about the difference between tree pruning and tree trimming before scheduling work.

Pruning should solve a specific problem. Avoid these common mistakes:

1. Do not top a mature tree.
2. Do not remove too much live canopy at once.
3. Do not leave long stubs or make flush cuts against the trunk.
4. Do not assume every species should be pruned on the same schedule.
5. Do not work near overhead utility lines.

Dead, damaged, or hazardous branches may need attention at any time of year. For routine care, professional tree trimming in Centennial can help determine which branches should be removed and which should remain.

Check your trees regularly for discoloration, fine webbing, wilted branch tips, premature leaf loss, and unusual bark changes. Spider mites and fire blight can spread before the damage becomes obvious from a distance.

Spider mites are tiny and often difficult to see. Their feeding may cause foliage to look speckled, dull, gray, bronze, or scorched.

Try this quick screening test:

1. Hold a clean sheet of white paper beneath a discolored branch.
2. Tap the branch firmly.
3. Watch for tiny moving specks.
4. Request a professional diagnosis if you see movement or widespread damage.

The University of Minnesota Extension’s spider-mite guide recommends this test as a practical way to detect mites. It is not a final diagnosis because beneficial mites and other small organisms may also fall onto the paper.

Mite activity varies by species. CSU Extension’s spider-mite resource explains that many species become active in warm, dry weather, while spruce spider mites often prefer cooler spring and fall conditions. Some can complete a generation in about 1 week, so populations may increase quickly.

Avoid spraying an unidentified pest. Some broad-spectrum insecticides can kill natural predators and make mite problems worse.

Adequate watering can help drought-stressed trees tolerate pest pressure. Fertilizer should be based on the needs of the tree and soil, not a fixed schedule. Professional tree fertilization can help address identified nutrient or soil concerns.

Fire blight affects apple, crabapple, mountain ash, and pear trees. The Colorado State University PlantTalk fire blight guide lists blackened shoots, wilted blossoms, and branch tips curled into a shepherd’s crook shape as common symptoms.

Infected branches may need to be removed below the visible damage, and pruning tools should be sanitized properly. Good watering, mulching, and plant selection also support long-term resilience. See our guide to eco-friendly tree care practices for more Colorado-friendly ideas.

A mature tree is not dangerous simply because it is large or old. Risk depends on the tree’s condition, the likelihood of failure, and what could be struck if a branch, trunk, or root system fails.

Centennial neighborhoods such as Willow Creek and Southglenn are known for mature canopies. These trees provide shade, privacy, and character, but they should be inspected when large branches extend over homes, driveways, sidewalks, or outdoor living areas.

Schedule an assessment if you notice:

• Dead branches over frequently used areas
• Cracks where major limbs meet the trunk
• Hanging or partly broken branches
• Mushrooms or visible decay near the base
• Soil lifting around the roots
• A new or increasing lean
• Cavities in the trunk or major limbs
• Recent wind, snow, or construction damage

The International Society of Arboriculture’s tree-risk guidance explains that risk may be managed through targeted pruning, routine care, support systems, moving potential targets, or removal when the risk cannot be reduced enough.

Crown thinning is not automatically the best solution. Excessive thinning can remove too much foliage without correcting problems in the trunk, roots, or major branch unions.

A professional recommendation may involve crown cleaning, reduction pruning, clearance pruning, cabling, monitoring, or removal. Before choosing a provider, learn more about the role of certified arborists in maintaining healthy trees.

Whether you are evaluating an ash tree, planning dormant pruning, investigating discolored foliage, or concerned about a large branch near your home, getting the right help early can make all the difference. At Richis Tree Service, we have served Centennial and nearby communities since 2005. We help homeowners assess tree health, reduce safety risks, and choose practical next steps for trimming, removal, stump grinding, and fertilization.

Do not wait for a weakened branch to fall or a declining tree to become an emergency. Call Richis Tree Service at (720) 987-5606 to request a free tree inspection.