The recent wildfires in California were horrific and devastating to homeowners and the economy. Many of the factors leading to this tragedy were beyond prevention: Climate change likely led to an unusually dry season, and a unique combination of wind events made the fires nearly impossible to control. These winds not only facilitated the fire’s rapid spread but also grounded aircraft that could have been used to suppress the flames.
One lesser-known and rarely discussed contributor to these fires is the presence of invasive plant species. Non-native plants, particularly grasses, have transformed California’s landscape into a virtual tinderbox. These deciduous grasses leave a layer of dead brush that enables fires to spread faster and farther than native vegetation would allow. “They have such a high surface area to volume and are very flat and thin, so they maintain a lot of dead standing material, almost all year round,” according to one professor at UC Santa Barbara. Another expert, commenting on the blanket of dead brush left behind said, “It’s so flammable that it takes any ignition—a cigarette, a spark from someone dragging a chain on the highway, or lightning.”
While wildfires are occurring at an increasing rate here in Connecticut, invasive plants are not a factor. That said, invasive plants can still harm our ecosystems, gardens, and local economy. Understanding the risks of invasive plants and how to stay ahead of them is important if we want to protect our environment and cultivate thriving landscapes.
The problem with invasive plants in Connecticut
Invasive plants are non-native species that spread aggressively, outcompeting native plants and disrupting ecosystems. As mentioned, invasive grasses facilitated the spread of wildfires in California, but other non-native plants contributed. Highly flammable Eucalyptus trees also created problems, so much so that there is talk of removing them from the state entirely.
Connecticut maintains a list of known invasive plants, and this past year several new species were added, including the callery pear tree, porcelain berry, mugwort, quackgrass, Japanese angelica tree, Japanese wisteria and Chinese wisteria. These plants thrive because they lack natural predators or controls, allowing them to dominate landscapes and crowd out native flora. While they may be popular because they’re pretty and easy to grow, the risks they pose far outweigh their benefits.

Because they thrive in our climate, these plants tend to choke out native plants. Why is that a problem? Our state’s wildlife depends on native plants for survival. In contrast, invasive plants may harm them. The black and pale swallow-wort, for example, is toxic to butterfly larvae and could reduce the population of these important pollinators.
Even more concerning is that some invasive plants can stifle the success of native plants through allelopathy. “That is the ability of a plant to give off a substance, either through its roots or through its leaves, that inhibits other plants — except its own kind — from growing near it,” Michael Nadeau, of Wholistic Land Care Consulting told NPR last year.
Invasive garlic mustard, which has become a problem in our area, has this ability. The Nature Conservancy reports that “garlic mustard’s roots release chemicals that alter the important underground network of fungi that connect nutrients between native plants, inhibiting the growth of important species like trees.”
Damaging biodiversity
Invasive plants have a destructive impact on biodiversity. Our native plants provide necessary food and shelter for Connecticut’s wildlife, from pollinators like bees and butterflies to birds and mammals. When invasive species take over, they disrupt these food webs, leaving native animals and helpful insects without critical resources. For example, oriental bittersweet and kudzu–both common invasives–are vines that can smother and kill trees, depriving birds of nesting sites and reducing the availability of native fruits and seeds. These vines can add so much additional weight to branches that it increases the risk of toppling trees during storms or heavy winds. Kudzu can grow up to a foot per day.

Invasive plants also degrade soil quality and alter water availability. Japanese knotweed can outcompete native plants along riverbanks, increasing soil erosion and degrading aquatic habitats. This can lead to poor water quality, affecting fish populations and other aquatic life. Knotweed is a particularly nasty invasive. As Estuary Magazine reports:
Despite its rapid and aggressive growth, knotweed fuels few food webs and displaces the native plants that can. There is some evidence that in addition to bullying existing vegetation in these areas, Knotweed also employs allelopathy—it releases chemicals that suppress the growth of would-be competitors. And the location next to moving water in riparian areas means that Knotweed—a plant capable of regenerating from a fingernail-sized sliver of stem or root—will readily ride the current to establish new plants further downstream.
Economic impact of invasive plants
Invasive plants are also costly. Homeowners, municipalities, and environmental organizations pay for removal and control efforts. By damaging trees and landscapes, these plants can also impact property values. (Japanese knotweed, which can infiltrate weak foundations and walkways, has been reported to reduce home values by up to 15% by one municipality in the Toronto area.)
Managing invasive plants on a broader scale, along highways or in public parks, may create a financial burden for taxpayers. Spotted knapweed, a common invasive in the US, is projected to cost more than $42 million annually to control.
An Oregon study assessed the potential economic impact of noxious invasive weeds and arrived at a total loss to the state of $83.5 million in a single year:
“We did predictive modeling in this study showing that if these noxious weeds were left to go everywhere they might go– if we did nothing to control them at their current levels– we could have a potential loss to the state of about $1.8 billion,” says Butler.
The economists who conducted the study used a variety of factors to derive a dollar amount, which is equated to personal income. Factors include livestock losses due to noxious weeds, reduced cattle foraging, reduced wildlife grazing, crop yields, decreased quality of seed and crop, potential impact on marketing and export of agricultural commodities, and even the loss of available fishing and hunting opportunities because of invasive weeds. The $83.5 million is the equivalent to the loss of 1,900 jobs and the $1.8 billion in potential losses if these weeds are unchecked is the equivalent to 40,800 jobs lost.
How to Identify and Address Invasive Plants
If invasive plants have taken root in your yard, acting quickly is essential to prevent them from spreading. Here are some tips:
Recognize common invaders:
- Japanese knotweed: Tall, bamboo-like stems with heart-shaped leaves; often found near water.
- Oriental bittersweet: Woody vine with bright orange and red berries that strangles trees and shrubs.
- Multiflora rose: A thorny shrub with arching stems and clusters of small white flowers in spring.
- Burning bush (Euonymus alatus): Popular–and historically purchased–as an ornamental plant, it turns a vivid red in the fall but, sadly, it also spreads aggressively in forests.

Download this poster of the most common invasives from the Connecticut Invasive Plant Working Group.
Safely remove invasive plants:
- Hand-pulling smaller infestations is often effective, but be sure to remove the entire root system to prevent regrowth.
- For larger infestations, you’ll probably need professional assistance, especially for species like Japanese knotweed, which can resprout from even the tiniest root fragments.
- Avoid composting invasive plants, as their seeds and roots may survive and spread further.
Prevent the spread:
- Inspect new plants carefully before adding them to your garden, and avoid purchasing known invasive species. (Most of these are now illegal to purchase.) Choose native plants where possible.
- Carefully clean your tools, boots, and even vehicles after working in areas with invasive plants to avoid transporting seeds to new locations.
Embrace native plants
Probably the best way to combat invasive plants is to replace them with native species. Native plants, by definition, are well-adapted to Connecticut’s climate and soil, so they naturally require less maintenance and benefit our local ecosystems. Here are some popular options:
Trees
- Eastern redbud (Cercis canadensis): This small ornamental tree grows stunning pink flowers in spring.
- Sugar maple (Acer saccharum): This robust tree is known for its vibrant fall foliage and value to wildlife.
Shrubs
- Highbush blueberry (Vaccinium corymbosum): Grow your own edible berries and enjoy beautiful foliage.
- Winterberry (Ilex verticillata): This deciduous holly boasts bright red berries that attract birds.
Perennials
- Purple coneflower (Echinacea purpurea): This striking purple bloom is popular with pollinators.
- Bee balm (Monarda didyma): Support your local pollinators! Bee balm attracts bees, butterflies, and hummingbirds with its vibrant red flowers.
Grasses
- Little bluestem (Schizachyrium scoparium): A drought-tolerant ornamental grass with lovely blue-green foliage.
- Switchgrass (Panicum virgatum): This grass adds texture and movement to gardens and provides habitat for wildlife.
Tips for Starting a Native Garden
- Assess your site
- Observe sunlight, soil type, and moisture levels to choose plants that will thrive in your yard. (We can help with this!)
- Plan for diversity
- Make it a goal to include a variety of trees, shrubs, and perennials to support a wide range of pollinators and wildlife.
- Source native plants responsibly
- Purchase plants from reputable nurseries that specialize in native species. Please don’t just dig up plants from the wild. This can harm natural ecosystems. (We know it’s tempting to grab your own milkweed.)
- Incorporate natural mulch
- Use organic mulch like shredded bark or leaf litter to suppress weeds, retain moisture, and improve soil quality.
- Fertilize naturally
- Feed your native garden with compost or compost tea to support growth.
A Greener Future for Connecticut
Invasive plants are a growing challenge (see what we did there?), but with awareness and action, we can protect Connecticut’s natural beauty and biodiversity. By removing invasive species and embracing native plants, homeowners can create landscapes that are both environmentally friendly and beautiful.
As we support our friends and families in California, we can also work together to preserve our local ecosystems—one garden at a time.
Support California Wildfire Victims: Donate to the Red Cross
Learn more about invasive plants in Connecticut from the Connecticut Invasive Plant Working Group