The Root Of The Problem Is The Roots

In 1978, the owner of Ross Tree noticed that visible tree-health problems above ground are actually symptoms of what is happening below the soil surface. He would say, “The root of the problem is the roots.” Front Range soils are great for growing grass, not trees, because they are naturally compacted, alkaline, and low in organic matter. Add our arid climate, and no wonder most of the trees seen in Denver are planted. Common issues such as thinning canopies, chlorosis (yellowing leaves), dieback, poor growth, and increased insect or disease pressure often trace back to compromised roots.

Human error is the primary cause of most tree root system issues. The most common is improper planting, when root collars or flares are below grade. Another planting mistake is forgetting that trees compete for water and space. Planting trees too close together leads to winners and losers as the trees mature. Some will thrive at others’ expense. Property owners need to fix any root issues first before addressing the canopy. Otherwise, the canopy problems will probably recur. When trees struggle, the real problem usually begins below ground.

Silver Maple Tree Root Problems

A hundred years ago, Denverites planted Silver Maples across the city to shade their homes because these trees grew fast and tall. However, the Silver Maple is no longer on the Denver Forester’s Approved Street Tree List because the trees hollow out and become unstable in their later years. Silver Maples, also known as Water Maples, naturally grow in river floodplains, stream banks, and swamps. Not a particularly good match considering our arid climate and heavy clay soils. Here, their roots tend to be shallow and exposed, spreading aggressively, damaging sidewalks and driveways, making them vulnerable to heat and drought. Mechanical damage exposes them to wood-decay fungi that can hollow out trees as they mature. What appear to be canopy or branch problems are usually delayed symptoms of long-term root stress, making root failure the actual underlying cause of decline. Call Ross Tree immediately if a large Silver Maple starts to lean.

Red Oak Tree Root Problems

Red Oaks are especially intolerant of buried root flares. Tree root flares are the part of the tree where the trunk transitions into roots. Root flares become buried by improper planting, covering the trunk with dirt, or over-mulching. Improper planting leads to girdling roots, gradually restricting water and nutrient movement. Denver’s alkaline, clay-dominated soils further exacerbate root stress by limiting nutrient availability, particularly iron, resulting in chlorosis. These Oaks respond poorly to soil compaction, construction disturbance, and inconsistent watering. In most cases, the visible health problems seen in these trees are the delayed outcome of long-term root failure rather than above-ground crown issues.

Honey Locust Tree Root Problems

Honey Locust trees in Denver are generally resilient and well-adapted to urban conditions, but are highly susceptible to drought stress, which weakens their ability to ward off disease. Thyronectria cankers are notorious for harming and killing Honey Locust trees. Cankers are dried-up areas on the stems and trunks that differ in color from the rest of the tree. The cankers are elongated and can occur on young or old wood. They become bumpy when the fruiting bodies of a fungus break through the bark. Disease symptoms include branch dieback, reduced foliage, premature fall coloration, and early leaf drop. Once abscesses appear on trunks, it is just a matter of time before the trees die. We are experiencing one of the driest winters in memory. Homeowners with Honey Locust trees should water their trees now. Click here for more information about tree cankers.

Colorado Blue Spruce Tree Root Problems

Like the Silver Maple, Colorado Blue Spruce are ubiquitous in Denver’s older neighborhoods. In the wild, Blue Spruces grow in cool, moist, well-drained soils with abundant organic matter and good air exchange. In Denver, they are typically planted in compacted, clay-heavy, alkaline soils that hold water, leading to oxygen deprivation. Over-saturated soils lead to rot and exposure to fungal pathogens such as Phytophthora. Affected trees wilt, their needles turn yellow/brown, branches die back, and the trees die, with symptoms that ironically mimic drought. Blue Spruces develop shallow, constrained root systems in urban settings. Big winds or heavy snowstorms can blow down Blue Spruces with compromised root systems. Root stress—not insects or foliage disease—is usually the primary driver of Blue Spruce decline in Denver.

Ponderosa Pine Tree Root Problems

Ponderosa Pines in Denver often struggle because our compacted clay soils restrict root penetration and air exchange, forcing roots to grow shallow and laterally, which reduces stability. Ponderosa pine prefers infrequent, deep watering and dry soil between irrigation cycles. In irrigated landscapes, frequent shallow watering keeps surface soils wet while depriving deeper roots of oxygen, increasing the risk of root decline and fungal issues. Over time, weakened roots reduce water uptake efficiency, leaving trees vulnerable during extended heat or drought despite regular irrigation.

Hackberry Tree Root Problems

Hackberry commonly suffers from buried root flares, often originating in the nursery or during planting. These trees tolerate this condition better than Red Oaks. Still, over time, it leads to reduced trunk taper, chronic stress, and slow canopy thinning as water and nutrient flow become restricted. Improperly planted Hackberries planted near sidewalks, streets, and driveways develop shallow, laterally confined root systems that can damage these hardscapes. Shallow roots are more vulnerable to heat, drought, and mechanical injury, reducing long-term vigor. Click here to find out more about Hackberry tree issues.

Ash Tree Root Problems

Ash trees make up about 15 percent of Denver’s urban forest. They develop several root-related problems caused by drought stress, compaction, and improper planting practices. Ash trees with compromised root systems decline faster when attacked by Emerald Ash Borer (EAB). Click here for more information about EAB and treatment options. Denver’s clay-heavy soils limit pore space and oxygen availability, which Ash roots need for healthy function. Ash trees are also sensitive to inconsistent or shallow irrigation. Frequent light watering encourages surface roots and discourages deeper structural rooting. During hot or dry periods, these shallow roots dry out quickly, causing feeder root loss and chronic water stress even when irrigation appears adequate.

Since most trees growing in Denver yards are not native, it makes sense that these plants need extra care throughout the year. Got a tree problem? Call 303-871-9121 or click here to complete a service request form.