Why Your Plants Are Turning Yellow in Colorado: A Complete Guide to Chlorosis

Rachel Arnold
Mar 2
3 min read

What Chlorosis Is and Why It Happens

When we talk about chlorosis we’re talking about leaves that turn yellow instead of green. The word literally means a lack of chlorophyll, which is the green pigment in leaves that allows plants to make their own food from sunlight in a process called photosynthesis. Without enough chlorophyll the plant can’t make the energy it needs to grow.

Many things can lead to chlorosis, but for most garden plants the root cause is a nutrient problem in the soil. Plants need nutrients like iron, nitrogen, magnesium, and manganese to produce chlorophyll. If those nutrients are missing or can’t be absorbed by the roots, the leaves go yellow.

A special kind of chlorosis we see a lot here is iron chlorosis. Iron is a micronutrient, meaning the plant needs just a little of it, but it is critical for making chlorophyll. Even if there’s plenty of iron in the soil, if it’s in a chemical form the plant can’t absorb, the plant still acts like it’s deficient.

What Chlorosis Looks Like in the Garden

Here are some typical signs:

Leaves are yellow or pale green instead of deep green.
Often the veins (the lines in the leaves) stay greener than the rest of the leaf. This pattern is called interveinal chlorosis.
Young leaves are usually the first to show symptoms with iron chlorosis because iron doesn’t move easily from old leaves to new ones.

If chlorosis is left unattended the plant will grow poorly, may drop leaves, and in severe cases the stems or limbs can weaken.

Why Colorado Soils Make Chlorosis More Common

Colorado gardeners know our soils are different from places with rich, dark, acidic garden soil.

Most Front Range soils are alkaline, which means they have a high pH (above 7.0). When soil is alkaline, even if minerals like iron are physically present, they chemically bond into forms plant roots can’t absorb. That’s why iron chlorosis is very common in Colorado landscapes.

You’ll notice evidence of high iron in Colorado soils if you’ve ever seen rust-colored rocks and dirt. There’s plenty of iron in the soil, but in alkaline soil it becomes insoluble – the roots can’t latch onto it and pull it into the plant.

Other common local factors that make chlorosis worse are:

Soil compaction or poor soil oxygen around roots
Overwatering or poorly drained soil
Competing plants or turf taking up nutrients
High levels of phosphorus or other nutrients interfering with iron uptake

What You Can Do in Your Yard

Because chlorosis is really about nutrients that the plant can’t absorb, starting with a soil test is the best first step. A soil test will tell you your soil’s pH and whether nutrients like iron are available to plants.

Some practical steps include:

Select plants suited to alkaline soil. Some species just handle high pH better than others.
Improve soil structure with organic matter to help roots explore and absorb nutrients.
Avoid excess watering, especially in spring when Colorado soils stay moist from snowmelt.
For established plants with chlorosis, iron chelates or foliar iron sprays can help. These special forms of iron stay soluble long enough for roots to take them up or leaves to absorb them.

Just remember that there isn’t a single quick fix for chlorosis in high pH soil; it’s often about caring for the soil and selecting plants that thrive in Colorado conditions.

A Few Helpful Terms to Know

Chlorophyll: The green molecule in leaves that lets plants convert sunlight into food. Without it leaves turn yellow.
Photosynthesis: The way plants use sunlight, water, and nutrients to make their own energy.
pH: A scale of how acidic or alkaline soil is. Below 7.0 is acidic, above 7.0 is alkaline. Most garden plants prefer slightly acidic to neutral soil.
Interveinal chlorosis: Yellowing of leaf tissue while the veins stay green. This often points to iron or manganese issues.

If you’re seeing yellowing in your plants and you’re gardening here on the Front Range, chlorosis is one of the first problems I would consider. Getting to know your soil and planting the right varieties for Colorado soil and climate will save you a lot of headaches and keep plants greener and happier.

Thanks so much for reading! Every yard in Colorado is a little different, and chlorosis can have more than one cause. If you have questions, stop by and talk with our Highland Garden Center experts. We will help you diagnose the issue and recommend the right solution for your specific plants and soil.

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