Denver’s trees need professional care because almost nothing about the city’s natural conditions is built for them. The air is dry, the soil is alkaline, temperatures can swing wildly in a single day, heavy wet snow tends to arrive when trees are fully leafed out, and emerald ash borer is now inside city limits. Most shade trees in Denver yards were planted, not native, and they depend on people to keep them going. This guide covers each of those pressures, what a trained arborist does about them, and where the line sits between what you can handle yourself and what’s worth calling in.
Quick answer: Denver gets about 14 inches of precipitation a year, according to the National Weather Service. Add alkaline soil, freeze-thaw swings, and snow-load damage, and many urban trees are under stress year-round. Professional care means correct pruning, watering and feeding based on the tree’s actual condition, early pest detection, and knowing when a tree can be saved and when it can’t.
Denver Isn’t Natural Tree Country
Before the city was built, the plains around Denver were mostly grassland. The planners behind Denver’s first Urban Forestry Strategic Plan put it plainly: the area’s “semi-arid climate and limited native tree species” have always made the urban forest “a careful balance of effort and intention.” The same work found that the city’s canopy was lagging behind comparable cities, with many young trees and limited species diversity. That combination leaves the whole urban forest more vulnerable to disease and extreme heat.
For homeowners, this means your maple, linden, or honeylocust is living somewhere it wouldn’t grow on its own. It can do well here, but it needs help.
The Five Pressures Working Against Denver Trees
| Pressure | What it does to trees | What professional care does |
|---|---|---|
| Low precipitation and dry air | Chronic drought stress, weaker defenses against pests and disease | Watering plans sized to the tree, deep-root feeding |
| Alkaline soil | Iron gets locked up, so leaves yellow (iron chlorosis) | Diagnosis, targeted treatment, better species choices |
| Temperature swings | Freeze damage before trees are ready for winter or after spring buds open | Assessing damage before pruning or removing anything |
| Heavy wet snow | Broken limbs and split trunks, especially on leafed-out trees | Structural pruning, cabling and bracing |
| Pests, especially emerald ash borer | Can kill untreated ash trees within a few years | Early detection, trunk injections, timed treatment |
Alkaline Soil and Yellowing Leaves
This is one of the most common problems Denver homeowners notice without knowing what it is. According to Colorado State University Extension, Colorado soils usually have plenty of iron, but they’re mostly alkaline, which keeps that iron “in an insoluble form not usable by plants.” The result is iron chlorosis: the newest leaves toward the ends of branches turn yellow while the veins stay green.
Maples (including silver, red, and Amur), red and swamp white oaks, aspen, and crabapples are among the most affected. The fixes aren’t simple. CSU notes that soil treatments have mixed results in high-lime soils and that trunk injections work but carry their own risks and should be done by a certified arborist. The tricky part is that yellow leaves can also point to overwatering, root damage, or pests, so the treatment depends on getting the diagnosis right first.
Wild Temperature Swings
Denver weather doesn’t ease trees into a new season. Ross Tree has seen widespread tree damage across the city from exactly this pattern. One October brought a roughly 70-degree drop, from the eighties to the low teens in a single day, before trees had hardened off for winter. That was followed by a nearly snowless, bone-dry winter and then a hard April freeze that hit new leaves and buds.
Damage like that often looks worse than it is, and sometimes it’s the other way around. A tree with brown foliage in spring may push new leaves a few weeks later. Another that leafs out normally may have dieback that shows up by midsummer. An arborist’s job is to tell the difference before anyone starts cutting.
Wet Snow, Broken Limbs, and Structural Pruning
Denver’s heaviest, wettest snow often shows up in spring, after trees have leafed out and are catching far more weight than a bare branch would. Cottonwoods, with soft wood and long limbs, break easily. Multi-stemmed ash trees collect snow in their crotches. Dense spruces and pines can snap under the load.
Cleaning up after a storm handles the immediate hazard, but it doesn’t fix why the tree failed. That’s what structural pruning is for: thinning and shaping the canopy to industry standards (ANSI A300) so it sheds snow and wind better. Most mature Denver trees benefit from it every three to four years, with fast growers needing it more often. For trees with weak unions that are worth keeping, cabling and bracing adds support without taking the tree down.
Water: More Than Most Homeowners Think
Lawn sprinklers don’t water trees well. Established trees need slow, deep watering that reaches the root zone. CSU’s general guideline is about 10 gallons per inch of trunk diameter, repeated every one to two weeks when it’s hot and dry. For a mature shade tree, that’s a lot of water, and most yard setups can’t deliver it properly.
Winter matters, too. Colorado often doesn’t get enough snow to keep soils moist, and Davey Tree recommends watering one to two times a month from October through March during dry spells. When Denver Water tightens lawn restrictions, trees and shrubs can generally still be watered by hand or with drip irrigation. Ross Tree covers the details in its guide to Denver water restrictions and your trees.
Emerald Ash Borer Raised the Stakes
Roughly one in six trees in Denver is an ash, according to Be a Smart Ash. Emerald ash borer was confirmed in Denver in 2025, and the city expects property owners to deal with ash trees on their own land. Denver doesn’t pay for treatment or removal on private property.
This is where professional care makes the biggest difference. A healthy ash can often be protected with trunk injections, which must be applied by someone licensed through the Colorado Department of Agriculture. Timing matters. Ross Tree explains why May 15 to June 15 is the critical treatment window. Once an ash has lost more than about 30% of its canopy, treatment usually stops being worth it, and removal becomes the safer option. Our 2026 homeowner guide to EAB in Denver walks through how to check your tree.
What You Can Do Yourself vs. When to Call an Arborist
Not every tree task needs a professional. Here’s a practical split:
| Usually fine to DIY | Worth calling a professional |
|---|---|
| Deep watering young and established trees | Pruning anything you can’t reach from the ground |
| Mulching (kept a few inches off the trunk) | Any work near power lines |
| Pruning small, low branches on young trees | Yellowing leaves, dieback, or thinning canopy you can’t explain |
| Keeping lawn equipment away from trunks | Ash trees, whether to treat or remove |
| Watching for changes season to season | Storm damage, cracks, or leaning trunks |
The rule of thumb: if the job involves a ladder, a chainsaw above shoulder height, a diagnosis, or a pesticide, it’s time for a professional.
Signs Your Tree Needs Professional Attention Now
- Thinning canopy or leaves that are smaller than usual
- Yellow leaves with green veins, or scorched leaf edges
- Leaves dropping early in summer
- Dead or dying branches, especially near the top
- Cracks, cavities, or holes in the trunk
- D-shaped exit holes or bark splitting on an ash tree
- A new lean, or soil heaving at the base after a storm
Catching these early is usually the difference between a treatment plan and a removal.
Why Denver Homeowners Trust Ross Tree
Ross Tree has been caring for Denver trees since 1978. The team includes two ISA Certified Arborists, and our Qualified Supervisors are licensed by the Colorado Department of Agriculture for pesticide and injection work. The company holds an A+ BBB rating and is a member of the Tree Care Industry Association. Services cover the full range Denver trees tend to need: pruning, plant health care, deep-root fertilization, insect control, and removal when there’s no better option.
Request a tree assessment and a certified arborist will tell you what your trees actually need, and what they don’t.
FAQ
Why is it hard to grow trees in Denver?
Denver is semi-arid, with about 14 inches of precipitation a year, alkaline soils that lock up iron, large temperature swings, and heavy spring snow. Most shade trees in the city aren’t native to these conditions and need supplemental water, correct pruning, and monitoring to stay healthy.
How often should Denver trees be professionally pruned?
Most mature trees in Denver benefit from structural pruning every three to four years. Fast-growing species like cottonwoods and silver maples may need it more often. Young trees benefit from early structural pruning to build strong branch structure.
Why are the leaves on my Denver tree turning yellow?
A common cause is iron chlorosis, where alkaline soil keeps iron from reaching the tree. It shows up as yellow leaves with green veins, usually on the newest growth. Overwatering, root damage, and pests can cause similar symptoms, so a proper diagnosis matters before treating.
Do trees in Denver need watering in winter?
Yes, during dry spells. Colorado winters often don’t provide enough snow to keep soil moist. A common recommendation is to water one to two times a month from October through March when the ground isn’t frozen and there’s been little moisture.
Should I treat or remove my ash tree in Denver?
It depends on its condition. Ash trees that have lost less than about 30% of their canopy are often good candidates for trunk injection treatment, applied by a licensed professional. Trees in worse condition are usually safer to remove before the wood becomes brittle.
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