Invasive Phragmites

Phragmites australis subsp. australis

Invasive Phragmites (European strain) is a tall, aggressive grass that can take over wetlands and shorelines, push out native vegetation, and reduce habitat quality for wildlife. The aggressive invader can also impact infrastructure such as roads, stormwater ponds, and agricultural ditches.


MAISRC findings

  • To date, more than 980 populations have been documented. Although that number is large, and has increased since the program began, the extent of invasive Phragmites is still relatively small, encompassing <100 acres.
  • Seed viability tests demonstrated that some populations in the southern two thirds of the state are sexually reproductive. The presence of viable seed increases the potential for further spread. Evidence from genetic testing has shown that there are a small number of hybrid populations in Minnesota. The presence of seed producing and hybrid populations is further reason to implement an effective control program as soon as possible.

Research

Developing a genomic method to detect hybridization between native and invasive Phragmites australis (common reed)

This project will develop a new method for detecting Phragmites hybrids by leveraging (1) genomic approaches developed for reed canary grass and invasive knotweeds and (2) native and invasive Phragmites samples already collected throughout the state and analyzed using microsatellite markers. 

Led by Dr. Daniel Larkin

Evaluating native Phragmites as a wastewater treatment alternative

The goal of the project is to support wastewater treatment facilities’ transition away from invasive Phragmites by systematically seeking native Phragmites strains with high dewatering ability.

Led by Dr. Daniel Larkin

Building scientific and management capacity to respond to invasive Phragmites (common reed) in Minnesota

This project mapped invasive Phragmites statewide, assessed its reproductive potential, and developed management protocols for responding to different invasion scenarios.

Led by Dr. Daniel Larkin


About Phragmites

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Description

Phragmites australis subsp. australis, also known as European common reed, is a tall, densely growing perennial grass that can take over large areas, push out native vegetation, and reduce habitat quality for wildlife. It can be found in wetlands, riparian areas, shorelines, and other wet areas such as roadside ditches. 

Both native and non-native genotypes of Phragmites are present in Minnesota. The native and non-native types can be difficult to distinguish from one another. For this reason, non-native Phragmites has been dubbed a “cryptic” invader. Without coordinated effort to distinguish and map native and non-native forms, the true distribution of invasive Phragmites in the state cannot be determined. This gap poses two risks: lack of action in response to new invasions or indiscriminate treatment that damages the native subspecies.

MAISRC has created a detailed identification guide to help you distinguish between native and invasive Phragmites

Management recommendations

Multiple years of treatment will be needed to achieve effective control of non-native Phragmites. Timely treatment with appropriate management techniques can be expensive, but will be more effective and save money in the long run compared to poorly timed and/or ineffective techniques. The following is an overview of a best practices management plan for non-native Phragmites control:

Summer mow (optional) —> Fall herbicide —> Winter mow —> Evaluate —> Follow-up treatment

View detailed management recommendations.

Impacts

Invasive Phragmites is an ecosystem engineer that benefits from human-caused disturbances on the landscape. Invasive populations in North America have been shown to alter the hydrology of wetland systems, lower plant diversity, impact food webs, and reduce diversity and abundance of invertebrates, fish, and waterbirds. 

Distribution

Phragmites has a global distribution, being found on all continents except Antarctica. The lineage that is invasive in North America – from the Atlantic coast westward to Minnesota and beyond – is native to Europe. This form has spread across North America over the past 150 years, almost entirely displacing native Phragmites in regions where it has long been established.

In 2017, more than 150 professionals and citizen observers requested kits to participate in the MNPhrag Early Detection Project. From its beginning in 2017 through 2020, the MNPhrag project has resulted in the documentation of over 550 unique populations of invasive Phragmites throughout Minnesota. See a map of verified populations in Minnesota documented by MAISRC researchers and their collaborators. 

How it spreads

Invasive Phragmites can spread both sexually (by seed) and asexually (clonally, including by stolon, rhizome, and stem fragments). When populations are producing large amounts of viable seed, spread across the landscape is more rapid and control is more difficult and expensive. The extent of sexual reproduction in Minnesota was investigated via viability studies, which showed that viable seed is being developed in several populations in approximately the southern two-thirds of the state. 

Targeted control of invasive Phragmites

The Minnesota Department of Natural Resources (MNDNR) and the University of Minnesota (U of M) are working to facilitate control of invasive, nonnative Phragmites throughout Minnesota, which is also home to a widespread native subspecies of this grass that is an important component of the state’s wetlands and shorelines. This effort relies on collaboration with state, county, and local municipalities and contractors who conduct the treatments. Private landowners play an important role when they recognize invasive Phragmites, report it, and permit access for treatment. To date, more than 980 populations have been documented. Although that number is large, and has increased since the program began, the extent of invasive Phragmites is still relatively small, encompassing <100 acres. Populations in some regions were already being managed by local authorities, while management in other regions is benefiting from this coordinated treatment program. 

To date, approximately 71% of known populations in the state have been treated at least once. Work in 2022 will include monitoring previously treated populations and conducting follow-up treatments as needed, along with implementing first-time treatments on additional populations. The goal is to ensure that all populations are under management to prevent further spread and protect Minnesota’s aquatic resources (and transportation and agricultural infrastructure) from this invasive subspecies.

If you have questions about the invasive Phragmites control program, please contact Julia Bohnen (U of M) or Wendy Crowell (MNDNR).

Project Team

U of M: Dan Larkin, Julia Bohnen
MNDNR: Heidi Wolf, Wendy Crowell

Funded by: Great Lakes Restoration Initiative (GLRI)

Project start date: 2020
Project end date: 2024