NORWAY MAPLE: THE SILENT BULLY BENEATH THE SURFACE

On the Hamilton-Wenham Regional High School campus, there is a silent bully at work: the Norway maple.

At first glance, the campus seems balanced—a manicured lawn, tall trees and bicycles lined outside the school. At the front of the building stands a Norway maple, its canopy wide and heavy, casting deep shade across the grass. Adjacent to it is a sugar maple, slightly smaller but nearly identical in shape. They look almost interchangeable. That similarity masks what is happening beneath the surface: below ground, one consistently outcompetes the other.

The Norway maple, an invasive species, was planted for a reason. It is fast-growing, resilient, and tolerant of compacted soil and urban conditions. It makes a campus feel complete—full, established, controlled. It looks like it belongs.

Ashley Keiser, a professor of soil and ecosystem ecology at the University of Massachusetts Amherst, said, “Norway maples are good as ornamentals because they are a fast-growing, early successional species.” But that appearance only tells part of the story, something I learned this year in my environmental science class as a junior at the high school.

In class, we came to understand that native species, like the sugar maple, matter because they are part of long-standing ecological relationships—trees, insects, soil, and wildlife all linked together in a system that has developed over time. When those native species are replaced with invasive species, like the Norway maple, it is not just a tree that disappears, but part of a network that keeps the ecosystem balanced and stable.

In an independent field study for my environmental science class, I compared data drawn from soil samples collected near both the Norway maple and the sugar maple trees. I took five samples around each tree, combined them into composite samples, and repeated the process twice a week over one month this spring. Soil test kits provide field estimates of pH and nutrient levels—low, medium, and high—rather than full laboratory analyses.

Across every sample, the pattern was consistent.

Nitrogen, essential for plant growth and chlorophyll production, was medium around the Norway maple but low around the sugar maple.

Phosphorus, which supports root development and energy transfer, showed the same divide: medium in the Norway maple’s soil, low in the sugar maple’s.

Potassium widened the gap—high around the Norway maple and low around the sugar maple—affecting how efficiently trees regulate water and withstand stress.

Even pH favored the Norway maple, measuring pH 6, or near neutral and nutrient-friendly. The sugar maple registered pH 5, a more acidic level at which nutrient uptake becomes more limited.

On the same campus, in the same soil system, one tree consistently holds the advantage while the other falls behind.

There is no single explanation for this.

Jennifer Forman Orth, an environmental biologist at the Massachusetts Department of Agricultural Resources, said the Norway maple’s success likely stems from a combination of factors, including competition, shading, and below-ground interactions.

But one mechanism stands out.

“There has been some research done that suggests allelopathy... may be a factor,” Orth said—referring to a phenomenon by which an organism—in this case the Norway maple—releases chemicals into the soil that can suppress nearby plant growth.

She also pointed to “antifungal chemicals that Norway maples release into the soil,” which may further shape what is able to grow in the surrounding area.

In other words, the tree may not only compete for resources—it may also be altering the conditions that determine what can survive beside it.

That ability to influence surrounding growth is one reason Norway maple is widely considered invasive.

Ken Druse, a garden writer who has studied the species, calls “the dreaded” Norway maples “terrible trees,” pointing to their ability to dominate both planted and natural landscapes.

Even without a single cause, the outcome is consistent. One tree thrives. The other struggles.

The imbalance builds over time. “Over time, soil conditions will reflect the properties of the plant species growing there,” Keiser said. Acer platanoides [Norway maple] would have different litter chemistry and plant-soil interactions compared to Acer saccharum [sugar maple].”

Put simply, the soil is not neutral. It is shaped by what dominates it.

Through the annual decomposition of leaf litter, Norway maples gradually shift soil conditions to resemble their own chemistry.

This dominance extends below ground as well. Norway maples develop shallow, aggressive root systems that spread through upper soil layers, absorbing water and nutrients before nearby plants can access them. They take resources first—leaving less behind over time.

“Unfortunately, this means that Norway maples can outcompete our native sugar maples by establishing themselves quickly and not allowing space for the sugar maples,” Keiser said.

That competitive advantage is part of why the species was added to the state’s Prohibited Plant List in 2005, a designation reflecting its ability to spread beyond cultivation and form dense stands that displace native trees.

Jacob Ahern, an environmental science teacher at HWRHS, said the Norway maples at the front and side of the building were planted decades ago—well before the species was placed on the state’s prohibited list. He said he is aware that the tree is considered invasive. There are currently no plans to remove or replace it.

What appears to be a balanced landscape is, in reality, uneven at nearly every level—light, nutrients, space, and soil chemistry.

What emerges is not a sudden collapse, but a slow, accumulating disadvantage that builds without notice.

The imbalance is already measurable.

The only question is whether anyone is paying attention—and why a tree known to outcompete native species remains in place at all.

NORWAY MAPLE: THE SILENT BULLY BENEATH THE SURFACE

Photograph taken by Cassi Sullivan