The Modesto ash was one of the most popular street and landscape trees planted across the Sacramento valley from the 1960s through the 1990s. It grew fast, provided good shade, and tolerated the valley heat. For decades, neighborhoods in Carmichael, Citrus Heights, Fair Oaks, and Sacramento were full of them.
Today, most of the mature Modesto ash trees we encounter are in serious structural decline — and in our professional opinion, the majority of them should be removed rather than maintained.
Here's why.
A History of Topping
The single biggest factor in the decline of Modesto ash trees across Sacramento is topping — the practice of cutting the main trunk and major limbs back to stubs.
Topping was widespread from the 1970s through the 2000s, often done by utility crews to clear power lines or by well-meaning homeowners and landscapers trying to reduce a tree's size. The problem is that topping is one of the most damaging things you can do to a tree.
When a tree is topped:
- Large wounds are left that the tree cannot properly close
- The tree responds by pushing out clusters of fast-growing, weakly attached sprouts from the cut sites
- Those sprouts grow into co-dominant stems — multiple leaders competing for dominance, attached at the surface rather than deeply integrated into the wood
- Decay sets in at the original cut wounds and spreads inward
In a Modesto ash, this process plays out over decades. The tree maintains a full, green canopy — it looks alive and healthy from the street — while the internal structure quietly deteriorates.
Included Bark and Hidden Decay
Co-dominant stems — the multiple leaders that develop after topping — frequently form with included bark. This is where bark tissue gets trapped between two stems as they grow together, creating a wedge that prevents the union from forming solid wood-to-wood contact.
Included bark unions are inherently weak. Unlike a proper branch union that becomes stronger as the tree grows, an included bark union can actually become more likely to fail over time as the stems grow larger and heavier. The bark wedge acts almost like a crack running through the joint.
In a topped Modesto ash, you often have multiple included bark unions throughout the canopy — each one a potential failure point.
Compounding this, the original topping wounds that never fully closed become entry points for fungal decay. That decay doesn't stay at the wound. It travels — down through the limbs, into the trunk, sometimes all the way to the root system. We regularly remove Modesto ash trees that have a full green canopy above and significant rot at the base and throughout the trunk below.
The Deceptive Green Canopy
This is the part that catches homeowners off guard: a structurally compromised Modesto ash can look perfectly healthy.
The tree is still producing leaves. The canopy fills out each spring. Nothing looks obviously wrong from the ground.
But structural failure in trees is rarely announced in advance. A stem with an included bark union can hold for years and then fail on a calm day — not during a storm, not under obvious stress, just because the wood finally gave way. When a major stem in a mature ash fails, it doesn't fall gently. It comes down with significant force, and it often takes fencing, vehicles, or structures with it.
The green canopy is not evidence that a tree is structurally sound. It only tells you the tree is still alive.
Signs Your Modesto Ash May Need to Come Down
If you have a mature Modesto ash on your property, look for:
- A flat or squared-off canopy — the telltale sign of past topping, even if it happened 20+ years ago
- Multiple stems of similar size originating from the same point — especially if they form tight V-shaped unions
- Visible cracks or splits at stem unions
- Fungal growth (mushrooms or shelf fungi) at the base or on the trunk
- Soft or spongy wood at the base of the trunk
- Dieback in the upper canopy — sections that don't leaf out in spring
- Previous limb failures — old wound sites where large branches have already come down
Any one of these warrants a closer look. Multiple together is a serious warning.
Can a Modesto Ash Be Saved?
In some cases — yes. A younger tree that was never topped, or a tree with good original structure and minimal decay, may have a reasonable lifespan ahead of it with proper care.
But for the majority of mature Modesto ash trees we see in the Sacramento area — the ones that were topped one or more times, that have been growing their replacement stems for 20 or 30 years, that have visible decay or included bark throughout — honest structural pruning will not fix the underlying problems. You can remove the most obvious hazard limbs, but you cannot undo decades of internal decay or restructure a union that formed with included bark.
In those cases, removal and replacement with a better-suited species is the right long-term decision for the property.
What to Replace It With
If you remove a Modesto ash, consider replacing it with a native or well-adapted species that won't create the same problems:
- Valley oak — the best large shade tree for the Sacramento valley, long-lived and structurally excellent when properly maintained from a young age
- Blue oak — drought tolerant, well-adapted to the valley, smaller scale than valley oak
- Interior live oak — evergreen, well-adapted, good structure
- Chinese pistache — not native, but widely planted, excellent fall color, good structure
Avoid fast-growing species that are commonly topped — the cycle tends to repeat.
TreeMax Can Assess Your Tree
If you have a Modesto ash and you're not sure what you're dealing with, we can take a look. We'll give you an honest evaluation — not a sales pitch for removal. If the tree has good structure and is worth maintaining, we'll tell you. If it's a liability, we'll tell you that too.