Invasive Plants in CT for Spring – CT Post Article

CT Post article by Jayden Nguyen, from April 29, 2025. Title: "Invasive plants pop up in CT for spring. Here's what to look for in your garden." with a picture of Japanese knotweed.

Invasive plants pop up in CT for spring. Here’s what to look for in your garden.

By Jayden Nguyen, Staff Writer

April 29, 2025

Guide to invasive plants in Connecticut

As spring flowers begin to emerge for the season, less desirable invasive plants are also starting to grow throughout Connecticut.

An invasive plant is a species of plant that is not native to the area and can cause environmental harm in “habitats that are not intensely managed,” according to Victoria Wallace, a sustainability, turf and landscape extension educator at UConn.

“In minimally-managed areas, invasive plants crowd out native plants,” Wallace said. “The presence of invasive plants alters the way plants, animals, soil and water interact within native ecosystems, often causing harm to other species.”

In Connecticut, there are some invasive plant species that are more common:

Herbaceous plants:

  • garlic mustard
  • Japanese knotweed
  • common reed
  • purple loosestrife
  • spotted knapweed

Woody plants (trees, shrubs and vines):

  • Japanese honeysuckle
  • tree-of-heaven (which attracts spotted lanternflies)
  • black locust
  • autumn olive
  • multiflora rose
  • Morrow’s honeysuckle
  • Japanese barberry

Wallace said that invasive plants typically have a high reproductive rate, the ability to disperse at wide distances and grow rapidly “under a wide variety of conditions.”

“Some invasive plants spread by seed, some by asexual reproduction,” Wallace said. “Invasive plants are often accidentally introduced to new locations through improperly treated mulch or compost, or seeds stuck on mowing (equipment) or other equipment.”

Wallace said that invasive plants’ seeds can also be dispersed via wind, water, vehicles, boats and birds or other wildlife.

Garlic mustard is one of the annual invasive plants that frequently comes up in the spring in Connecticut, Wallace said. The Connecticut Invasive Plant Working Group, or CIPWG, provides a calendar for invasive plant management, so that gardeners can identify when certain types of invasive plant species are more likely to grow and the best methods for removing them.

Wallace said that once gardeners identify the invasive plant species growing in their gardens, there are several ways that they can be removed.

Removing and controlling invasive plants from a garden

“Invasive removal can be done via a combination of mechanical and chemical controls,” Wallace said. “The best control methods depend on the species, time of year and the site.”

If dealt with early enough, Wallace and UConn’s CIPWG said that most invasive plant species should be able to be removed with non-chemical methods. Herbicides, or weed killers, may be necessary to remove infestations of invasive plants that have become well established or widespread.

Wallace said that flame weeding can help remove invasive plants, although she does not recommend using flame weeding in windy or dry weather conditions. Biocontrol, or biological control, is another method that Wallace recommended. Biocontrol involves using certain insects or pathogens, such as fungi and viruses, to control unwanted insects, weeds or diseases, according to UConn’s College of Agriculture, Health and Natural Resources.

Gardeners can also grow plants that are native to Connecticut to help remove and replace non-native invasive plants.

“Every plant is native to some location. When a plant is grown outside of its original location, it is usually classified as a non-native plant,” Wallace said. “Some people really try to focus on plants native to Connecticut, however, it’s perfectly okay to mix native and non-native plants in the landscape, as long as the non-natives are not invasive.”

There are several types of plants that are native to Connecticut that gardeners can grow to remove invasive plants, including perennial plants — which grow and bloom each spring and summer — and woody plants, Wallace said.

“Some great options for perennials include goldenrods, asters, Joe Pye Weed, bee balm, mountain mint – these all are easy to grow and great for pollinators,” Wallace said. “Some woody natives that are easy to grow and beneficial for pollinators include maples and oaks, summersweet, blueberry, northern bush honeysuckle and spicebush.”

Wallace and CIPWG said that controlling invasive plant species is important to prevent “biological pollution” and “reduce negative impacts” on natural ecosystems in Connecticut and throughout the U.S. Wallace said that she suggests for Connecticut gardeners to “increase the number of native species” of plants in their gardens to help decrease the spread of invasive plants.

“Choose plants native to Connecticut to allow native pollinators greater access to and more diversity in their source of food throughout the growing season,” Wallace said. “A healthy and landscape provides both protection and a diversity of food sources for our beneficial insects.”

Guide to invasive plants in Connecticut

Here are some of the invasive plants you may find in your garden this season.

Herbaceous Plants

  • Garlic mustard
  • Common reed
  • Purple loosestrife
  • Spotted knapweed
  • Japanese knotweed

 

Woody Plants (trees, shrubs, vines)

  • Japanese honeysuckle
  • Morrow’s honeysuckle
  • Multiflora rose
  • Japanese barberry
  • Autumn olive
  • Tree-of-heaven
  • Black locust
  • Norway maple
  • Black swallow-wort
  • Winged euonymus (burning bush)

Read more at CT Post

CIPWG in the News: Article in The Day

An article by Kathy Connolly was published in The Day entitled: Your Turn: Invasive-plant symposium gets in the weeds, literally.

“Warm weather and above-average rainfall made our 2024 gardens grow but also encouraged invasive plants. Invasives are not just any weeds. They are non-native plants that take advantage of landscape disturbances such as excavation, movement of soil, overpopulation of deer, or the spread of invasive worms. Though the initial disturbances may seem inconsequential, these plants gain a toehold and then quickly change landscapes for the worse. Familiar examples include Japanese knotweed, stiltgrass, and bittersweet.”

Read more at: https://www.theday.com/columns/20241008/your-turn-invasive-plant-symposium-gets-in-the-weeds-literally/

You can also access a pdf of this article at: Your Turn_ Invasive-plant symposium gets in the weeds literally

Good News on Recent Invasive Plant Legislation

Over the past year, a CIPWG subcommittee reviewed the CIPWG research list (plants that were being studied to determine invasive potential) and made recommendations to the Invasive Plants Council (IPC) regarding plants that should be moved to the invasive plant list. The IPC is the state-mandated body that recommends changes or updates in invasive species legislation to the CT legislature through the Environment Committee (EC).

In the IPC annual report, the IPC made recommendations to the EC. The EC followed the suggestions of the IPC and submitted a bill (HB 5225) to the legislature. It passed through the house and senate and the governor signed the bill into law this Tuesday (5/14).

The bill includes:

  • Callery pear (Pyrus calleryana) will be added to the CT invasive plant list with a 3-year phase out period; it will be prohibited from sale as of October 2027.
  • Quackgrass (Elymus repens) and Japanese angelica tree (Aralia elata) will be added to the invasive plant list and prohibited from sale as of October 2024.
  • Japanese wisteria (Wisteria floribunda) and Chinese wisteria (Wisteria sinensis) will be added to the potentially invasive plant list and prohibited from sale as of October 2024.
  • Porcelainberry (Ampelopsis brevipedunculata) and Mugwort (Artemisia vulgaris), which are already on the invasive plant list, will be added to the prohibited from sale list as of October 2024.

You can read the text of the bill, view testimony, votes of CT legislators, and more at cga.ct.gov.

We, the CIPWG co-chairs, are thrilled to see CIPWG, the IPC, and the Environment Committee work together in such an effective way to make progress on regulation of invasive plant species in CT.

We are grateful for the efforts of CIPWG members, the IPC, and the Environment Committee for the continued effort to take meaningful steps to regulate invasive plant species in our state.

We are in the process of updating the Invasive Species list with the changing regulations and will keep posted on those updates as they are completed.

Vickie Wallace, Rose Hiskes, and Emmett Varricchio, CIPWG Co-chairs
info@cipwg.org

Read CIPWG’s 2023 Annual Report

Thank you for reporting your 2023 Invasive Plant Activity!

The CIPWG 2023 Annual Report is a compilation of reported invasive plant management and education activity for the 2023 year.

Read the 2023 CIPWG report HERE

 

The report details the invasive plant management and educational activities that occurred in over 60 CT towns throughout the year. At least 5,345 citizens directly and actively participated in the activities reported. Many (at least 4,670) were reached indirectly through articles, YouTube videos, social media, fact sheets, signs, and other educational mediums. A minimum of 30,765 hours were directly invested in invasive plant management, during intensive invasive plant training sessions and management activities, as well as educational outreach. A minimum of 5,300 hours were provided indirectly as citizens engaged in educational efforts and learned from videos, articles, and fact sheets.

The Connecticut Invasive Plant Working Group maintains the following subcommittees:

  • Education and Outreach (educational outreach about invasive species and their alternatives)
    • CIPWG display was used at 5 events around the state in 2023.
    • Outdoor Educators held 6 free “Walk, Talk and Cut” events in 5 of Connecticut’s counties. 74 people attended these events.
  • Management (develop and disseminate information on invasive plant control options)
  • Native Alternatives (explore and promote use of native plant species as alternatives to invasives)
  • Research List Review
    • Met 5 times in 2023 to review CIPWG’s Research Plant List.
    • Made recommendations to the CIPWG Steering Committee regarding plants that should be recommended to the Invasive Plant Council for addition to the CT Invasive Plant list.
    • Developed protocol for annual review of the Research List.

CIPWG provides a List of Speakers who are available to give presentations on many invasive plant-related topics, including identification, control, and non-invasive alternatives. Since 2002, CIPWG has hosted biennial invasive plant symposia. Symposium 2022 information is available on the CIPWG website.  Planning for the 2024 biennial CIPWG symposium has begun.

FALL 2019 CIPWG General Meeting- Oct 24 2019

CIPWG Fall General Meeting, October 24, 2019, 1:00 – 3:00 pm

– free and open to all interested individuals

– Tolland County Agricultural Center, 24 Hyde Ave., Vernon, CT

Come hear updates on invasive plants and native alternatives in Connecticut.

Special Guest Speaker, Annise Dobson,   Asian Jumping Worms 101: 

Identification, Impacts on Plants and Ecosystems, and Steps Toward Solutions

Full Agenda    Driving Directions

 

2018 CIPWG Symposium Podcasts

To listen to recent podcasts about the upcoming CIPWG Symposium, click the links below:

  1. Donna Ellis interviewed with John Voket from Connoisseur Media:

 

https://audioboom.com/posts/6992071-invasive-plants-symposium-protecting-the-sound-informct-consumer-survey-q2

 

  1.  Charlotte Pyle and Judy Preston were interviewed by Suzanne Thompson with CT Outdoors:

 

http://www.wliswmrd.net/ – click on “On Demand” and scroll through Podcasts to 8//28/18 podcast.