Hennepin Marsh Gateway Remediation Project
The Hennepin Marsh Gateway, owned by the Grosse Ile Nature and Land Conservancy (GINLC), has become overrun by non-native invasive plants. These plants have a significant negative impact on the environment, including reducing habitat for native plants and animals and decreasing native biodiversity. They also tend to grow thick and tall, reducing visibility for Grosse Ile residents.
The non-native invasive plants at the Hennepin Marsh Gateway include Common Reed (Phragmites australis) and Bush Honeysuckle (Lonicera spp.). The abundance of Phragmites has been particularly concerning because it has grown so thick and tall that it has reduced habitat for native plants to grow and it has blocked the visibility of the Detroit River.
In addition to the presence of invasive species, we needed to remove approximately 20 trees that died during the high water that we experienced in the past few years. The most noticeable were the five large cottonwood trees that died. All of these trees were removed for safety reasons.
Removing Phragmites from the wetland.
The Monday Morning Stewardship Crew has been able to work most Mondays for the past several months. They have made great progress on the restoration work at Hennepin Marsh Gateway Preserve. Most of the dead trees and invasive plants, mainly phragmites and honeysuckle, have been removed. It will be interesting to see how the preserve comes alive in the Spring when the trees leaf out and the marsh grasses return. It will be several years, however, before the restoration work at the preserve is completed.
​
We are executing a plan to control invasive plants at the Hennepin Marsh Gateway. This will be a multi-year effort, as invasive plants are persistent and require several years of control. After initial control is achieved, ongoing yearly control will be required to ensure that the invasive plants do not return and dominate the site once again.
The plan involves repeated mowing and cutting of invasive plants followed by herbicide treatment. Mowing/cutting will improve views for visitors and will enable easier control of invasives in the future. The herbicide will be applied to the leaves of herbaceous and woody invasive plants and to cut woody stumps. Only herbicides approved for aquatic environments will be used. Herbicides will be applied by professionals with a Commercial Pesticide Applicator License.​
Cutting Phragmites
The invasive species control measures will be implemented as follows:
2022: Initial control period
-
Summer: Mow or cut invasive plants.
-
Late-summer/fall: Initial herbicide treatment. At least two treatments/year.
-
Fall: Continued cutting of invasive woody invasive plants.
2023:
-
Winter/spring/summer: Mowing/cutting of invasives, as needed.
-
Summer/fall: At least two herbicide treatments/year.
2023 - and beyond:
This process will continue yearly until the abundance of non-native invasive plants has been significantly reduced. Once control has been achieved, we anticipate limited cutting and herbicide treatments (approx. once per year) to keep the invasive plants from returning.
​
After these control measures have taken effect, we anticipate native plants will once again germinate at the site. Depending on the abundance of native plants, we may consider seeding or planting herbaceous or woody native plants to improve native plant diversity and wildlife habitat.
One of the preserve's residents
We are committed to protecting the Hennepin Marsh Gateway and restoring it to its natural state. We appreciate your support as we work to implement this project.
Most invasive plants cut down and removed. Spring 2023
Invasive plants awaiting chipping. Spring 2023