Tree Chlorosis in Colorado: What It Is, Why It Happens, and How to Fix It

Tree chlorosis is one of the most common and frustrating tree health problems Colorado homeowners face. If you’ve noticed your maple, oak, or shade tree turning yellow instead of staying lush green, you’re looking at more than a cosmetic issue. You’re seeing a warning sign of stress.

Colorado’s unique soil chemistry, climate, and urban environments create the perfect storm for chlorosis… but the good news is: with the right professional treatment, most chlorotic trees can recover.

This guide explains everything Colorado homeowners should know about chlorosis, including causes, early warning signs, treatment options, and how to keep trees healthy long-term.

What Is Tree Chlorosis?

Chlorosis is the yellowing of leaves caused by insufficient chlorophyll. Chlorophyll is what gives leaves their green color and allows trees to photosynthesize (convert sunlight into food). When a tree cannot produce enough chlorophyll, it becomes weak, stressed, and vulnerable to insects, disease, and decline.

In maple trees especially, chlorosis commonly affects the interveinal areas (the space between the veins). The veins stay dark green while the rest of the leaf turns pale and is a hallmark symptom homeowners notice first.

Chlorosis is not a condition by itself it’s a symptom telling you something deeper is wrong.

Why Is Chlorosis So Common in Colorado?

Colorado is a chlorosis hotspot, especially along the Front Range (Fort Collins, Greeley, Loveland, and surrounding communities). There are three main reasons:

Colorado’s Soil Is Highly Alkaline

Most Colorado soils have a naturally high pH (7.5–8.5+). Iron is often present in the soil, but at high pH levels, trees cannot absorb it. This leads to functional iron deficiency which is the #1 driver of chlorosis in Colorado.

Clay & Compacted Soil Conditions

Much of Colorado’s soil is:

• Dense
• Hard-packed
• Poorly aerated

This restricts root growth and limits nutrient absorption, especially in newer subdivisions where native soils were disturbed during construction.

Colorado Climate Stress

Colorado trees endure:

• Intense summer heat
• Bitter winter cold
• Rapid freeze-thaw cycles
• Frequent drought conditions
• Limited rainfall
• High elevation UV exposure

All of these stress the tree’s ability to sustain chlorophyll production.

Trees in Colorado Most Commonly Affected by Chlorosis

While ANY tree can develop chlorosis, these Colorado species are most at risk:

Many of these species were not naturally adapted to Colorado soils, which is why they struggle here without supplemental care.

Early Warning Signs of Chlorosis Homeowners Should Watch For

Many homeowners don’t realize they’re seeing early chlorosis until the tree is severely declining. Catching it early is critical.

Common symptoms include:

If your tree’s leaves are yellow but veins remain green, that is a strong indicator of nutrient-related chlorosis.

Is Chlorosis Dangerous for Trees?

Yes, when ignored.

Chlorosis isn’t “just ugly.” Without intervention, chlorotic trees experience:

• Reduced energy production
• Increased vulnerability to insects & disease
• Structural weakness
• Decline and die-back
• Premature death

We regularly see untreated chlorosis kill large shade trees in Colorado trees that could have been saved with timely treatment. Considering the cost of tree removal and replacement can reach thousands of dollars, early chlorosis treatment is almost always the smarter investment.

Diagnosing Chlorosis: What Professionals Look For

A professional tree care evaluation typically includes:

• Visual inspection of leaf color and pattern
• Species-specific susceptibility analysis
• Soil condition assessment
• Irrigation review
• Health history and environmental stress factors

In some severe or unclear cases, soil or tissue testing may be recommended to confirm nutrient levels.

How Is Tree Chlorosis Treated in Colorado?

Effective chlorosis treatment focuses on correcting nutrient deficiency and improving long-term soil health. The best solution depends on severity.

Deep Root Fertilization

Nutrient-rich liquid fertilizer is injected directly into the root zone.

Benefits include:

• Improved nutrient uptake
• Stronger, healthier root development
• Thicker, greener foliage
• Improved drought resistance

Iron Treatments (Including Iron Injections)

For chlorotic maples and oaks, iron supplementation is often essential. Depending on the situation, professionals may recommend:

• Soil iron amendments
• Iron chelate applications
• Tree trunk iron injections for severe cases

Trunk injections provide fast, direct nutrient delivery and are often the best solution for trees with significant chlorosis.

Pest & Disease Protection

Stressed trees attract pests. Seasonal protection helps safeguard recovering trees and prevent additional decline.

Soil Aeration & Root Zone Improvement

Relieving soil compaction improves oxygen flow and allows roots to function more efficiently.

How Long Does It Take to See Improvement?

Many Colorado homeowners begin seeing noticeable improvement within a season and dramatic transformation within a year.

For example:

• Before: Pale yellow canopy, thinning foliage, weak appearance.
• After: Full, vibrant green canopy with restored health and stronger growth.

However, severe chlorosis cases may require ongoing care to prevent relapse especially in species that naturally struggle in Colorado soils.

Can Chlorosis Fix Itself?

Almost never in Colorado because the underlying problem is our soil chemistry, chlorosis rarely resolves without intervention. In fact, it almost always worsens over time.

Preventing Chlorosis in Colorado Trees

The best strategy is proactive care:

Healthy trees cost far less to maintain than sick ones cost to save.

Protect Your Colorado Trees from Chlorosis

If your tree is yellowing, thinning, or showing signs of stress, now is the best time to act. Chlorosis is highly treatable in Colorado as long as it’s handled correctly.

Professional Tree Chlorosis Services in Colorado

Here at American Turf & Tree Care, we offer free tree care quotes and our service looks like this:

Your trees are one of the most valuable parts of your landscape. Let’s keep them strong, green, and thriving year after year. Contact us today to learn more about our tree care services.