A foliage forecaster for Yankee Magazine recently noted, “There are threats on all sides to what we consider a beautiful New England forest.” In an interview with WCVB 5 News, three major drivers were identified: climate change, invasive insects, and invasive plants.

Peer-reviewed research supports this concern. Science is showing how, as invasive plant species expand beyond their native ranges, they can alter ecosystem structure and competitive dynamics, contributing to long-term changes in forest composition. Together, scientific evidence and regional reporting point to a measurable shift in the composition and resilience of New England’s forests.

In New England, invasive plants most often threaten forest regeneration and canopy stability. While mature trees may survive for years, invasive vegetation suppresses seedling growth, smothers young trees, girdles trunks, and alters soil conditions, gradually shifting the future composition of New England forests. 

New England’s fall foliage industry generates billions of dollars annually in tourism revenue, and the vibrant autumn colors are also one of the reasons so many people choose to live here. Invasive vegetation threatens not only biodiversity but also the regeneration of the very tree species that define the region’s forests, landscapes, and economy.

Unchecked invasive growth does not simply crowd out native New England plants, they prevent new ones from germinating, gradually reshaping the future tree canopy of Massachusetts.

Native Horizons exists to help maintain New England’s native landscapes by helping people and native vegetation thrive together. Through responsible vegetation management, we aim to give people and native vegetation a brand-new horizon. For other impacts of invasive plants on New England, read further.

Below is a list of most vulnerable trees.

If you are considering planting a tree, consider planting one of these.

1. Sugar Maple

Fall Color: Brilliant orange, red, and gold
Economic Contribution: Foundation of New England’s maple syrup industry and a major driver of fall foliage tourism

Most Harmed By:

• Garlic mustard (disrupts mycorrhizal fungi critical to seedlings)

• Porcelain berry (overwhelms young trees and shades seedlings and saplings)

• Norway maple (direct canopy competitor)

• Japanese barberry (dense understory suppression)

• Japanese knotweed (threatens riparian corridors where regeneration occurs)

Sugar maple regeneration is highly sensitive to soil chemistry disruption and light competition, making it one of the most vulnerable long-term canopy species.

2. Northern Red Oak

Fall Color: Deep red to russet
Economic Contribution: High-value hardwood used in flooring, cabinetry, and construction

Most Harmed By:

• Japanese barberry (takes necessary resources like light and moisture from seedlings)

• Multiflora rose (crowds out and physically blocks seedlings) 

• Porcelain berry (overwhelms young tress and shades seedlings and saplings)

• Garlic mustard (alters forest soils making them less hospitable to seedlings)

• Oriental bittersweet (girdles trees, creates canopy stress and suppresses seedlings)

Oak seedlings require light and space; dense invasive thickets dramatically reduce successful regeneration.

3. White Oak

Fall Color: Redish-brown to purple-red
Economic Contribution: Premium hardwood used in furniture and cooperage

Most Harmed By:

• Japanese barberry (takes necessary resources like light and moisture from seedlings)

• Glossy Buckthorn (takes necessary resources like light and moisture from seedlings)

• Multiflora rose (thorny colonies that crowd out young seedlings)

• Porcelain berry (overwhelms young tress and shades seedlings and saplings)

• Garlic mustard (damages soils and creates dense spring groundcover)

• Oriental bittersweet (girdles trees, creates canopy stress and suppresses seedlings)

White oak regeneration declines significantly under invasive shrub dominance.

4. Eastern Hemlock

Fall Color: Evergreen (deep green year-round)
Economic Contribution: Essential for watershed protection and cold-water fisheries habitat

Most Harmed By:

• Japanese barberry (takes necessary resources like light and moisture from seedlings)

• Multiflora rose (thorny colonies that crowd out young seedlings)

• Porcelain berry (overwhelms young tress and shades seedlings and saplings)

• Oriental bittersweet (girdles trees, creates canopy stress and suppresses seedlings)

• Japanese knotweed (largely streamside stands and regeneration suppression)

Hemlock seedlings struggle in dense understory conditions created by invasive shrubs and vines.

5. Red Maple

Fall Color: Bright red to scarlet
Economic Contribution: Important hardwood species and contributor to foliage tourism

Most Harmed By:

• Norway maple (direct competitor)

• Porcelain berry (overwhelms young tress and shades seedlings and saplings)

• Japanese barberry (takes necessary resources like light and moisture from seedlings)
• Garlic mustard (damages soils and creates dense spring groundcover)

• Oriental bittersweet (girdles trees, creates canopy stress and suppresses seedlings)

• Japanese knotweed (regeneration suppression and riparian areas)

Red maple is more adaptable but still suppressed under dense invasive competition.

6. American Beech

Fall Color: Golden bronze
Economic Contribution: Important wildlife mast producer and native forest component

Most Harmed By:

• Japanese barberry (takes necessary resources like light and moisture from seedlings)

• Porcelain berry (overwhelms young tress and shades seedlings and saplings)

• Garlic mustard (damages soils and creates dense spring groundcover)

• Oriental bittersweet (girdles trees, creates canopy stress and suppresses seedlings)

• Multiflora rose (crowds out and physically blocks seedlings)

Beech seedlings are easily suppressed by invasive groundcover and shrub layers.

7. Eastern White Pine

Fall Color: Evergreen
Economic Contribution: Keystone species which acts as the physical and biological anchor of the northern mixed-wood forest.

Most Harmed By:

• Japanese barberry (takes necessary resources like light and moisture from seedlings)

• Glossy Buckthorn (takes necessary resources like light and moisture from seedlings)

• Porcelain berry (overwhelms young tress and shades seedlings and saplings)

• Garlic mustard (damages soils and creates dense spring groundcover)

• Oriental bittersweet (girdles trees, creates canopy stress, encourages canopy failure and shades seedlings)

• Multiflora rose (crowds out and takes space and resources from seedlings)

One of the most sensitive native conifers to understory competition from invasive plants. Seedlings require part-sun to part-shade to grow.

Invasive plants can cause serious problems for local landscapes. They can:

• Crowd out native plants by taking the light, nutrients, and space they need to grow

• A single type of plant, such as garlic mustard or Japanese knotweed, can form large dense patches that push out other vegetation, reducing plant diversity

• Change the health of the soil, making it harder for native plants to grow

• The loss of native plants disrupts food sources for native insects, birds, and native animals that depend on native plants

• Invasive plants increase erosion, especially along streambanks and slopes

Healthy watersheds are critically valuable because they:

• filter and clean water
• reduce flooding and erosion
• recharge groundwater
• stabilize streambanks
• support fisheries and wildlife
• regulate water temperature
• store carbon
• and sustain forests, agriculture, and drinking water supplies

Invasive plants can severely damage watersheds by displacing deep-rooted native vegetation, reducing biodiversity, destabilizing soils and streambanks, altering water flow and nutrient cycling, increase erosion and sedimentation, degrade wildlife habitat, and reduce the ecological resilience of forests and wetlands.

In New England especially, healthy native vegetation within watersheds helps protect cold-water streams, forest health, flood resilience, water purity for all organisms (including human), and overall ecosystem stability. 

When plant diversity declines, the health of the entire landscape declines with it, plants, insects and animals. And, though slowly overtime, us with it!

Native plants support complex food webs that insects, birds, and wildlife rely on. Invasive plants do not.

Some invasive species cause direct physical damage:

• • Japanese knotweed forms dense rhizome networks that can exploit cracks in pavement, home foundations, and retaining walls. We have had to climb into basements to eradicate Japanese knotweed. 
  • Oriental bittersweet climbs and girdles trees, increasing windthrow risk and canopy collapse potentially damaging homes or buildings.
  • Aggressive vines and shrubs can also add weight to tree canopies, increasing storm vulnerability.

Over time, unmanaged infestations can lead to tree loss, slope destabilization, drainage disruption, prooperty damage, and increased long-term maintenance costs. As infestations spread, they increase maintenance costs, damage trees and structures, reduce property value, and require more intensive long-term management.

Aggressive vines such as bittersweet and porcelain berry can girdle and weaken mature trees, raising storm-failure risk, costly removal expenses and property damage. Dense invasive shrubs, like multiflora rose and Japanese barberry, crowd out lawns and garden beds, block sightlines, restrict access to portions of the property, and create ideal conditions for ticks and other pests.

Local municipalities and conservation groups also bear rising control and restoration expenses, which ultimately affect local budgets and taxpayers. Addressing invasive vegetation early protects both environmental health and financial investment.

Invasive species, including plants, cost the United States an estimated $20 billion or more annually in management expenses, infrastructure damage, agricultural losses, and ecological restoration efforts. These costs include public land management, reduced crop and timber productivity, damage to roads and foundations, and long-term environmental degradation.

These invasive species alter forests, wetlands, and agricultural lands, weaken native plant communities, and increase long-term restoration costs.

What begins as a localized infestation can contribute to broader environmental and economic strain across the country.