September 16, 2015
Kimberly Bourke, U.S. Geological Survey, Contractor
Non-native Phragmites australis dominates inland and coastal wetlands as well as other wet areas, such as roadside ditches, throughout the Great Lakes region. Management of non-native Phragmites regularly includes herbicide application, which will successfully kill this plant. However, many management resources do not address the abundance of aboveground biomass left after herbicide treatment and the question remains: what should be done with all of the dead non-native Phragmites biomass? There are several options, and individual managers should chose options that work best for them, depending on the situation at hand, the size of the stand, and the resources and tools available. This blog summarizes pros and cons of a few possible options, as well as links for more information:
- Pros: Little time, energy, and resources needed.
- Cons: The standing dead non-native Phragmites plants shade the soil and create a physical barrier, which makes the environment less suitable for colonization and regrowth of desirable plants. Leaving the standing dead plants can also make herbicide spot treatments less efficient in the following years (See Bob Williams’ webinar for more information on this side effect). These same standing dead Phragmites may also become a fire hazard.
- Pros: Mowing stands that have been sprayed with herbicide will help to make future spot treatments easier (see above option).
- Cons: Depending on conditions, accessing some areas with a mower can be difficult, if not dangerous. Also, mowing does not actually remove any biomass, which continues to shade the soil and make it difficult for more desirable plants to establish. Dried out biomass left onsite may also become a fire hazard.
Pros: Burning standing dead non-native Phragmites plants is a commonly used technique, especially after herbicide application. It is a fast and effective way to remove this Phragmites biomass and clear the soil surface to allow for seed germination of other desirable plants. Professional agencies frequently use burning as part of their management plans (See Lee Osterland’s two part webinar on burning non-native Phragmites: Part 1, Part 2).
- Cons: Burning non-native Phragmites creates an extremely hot and smoky fire that produces greenhouse gas emissions and particulate matter. As a result, some places do not allow burning of these Phragmites stands by law or ordinance. Special equipment, extensive training and a permit are all typically required to complete the work.
Bag & Trash
- Pros: Easily used for small patches of non-native Phragmites. Leaving the bags of plants out in the sun will kill the plants, and reduces the risk of further spreading.
- Cons: Adding plastic bags full of plant material increases inputs to landfills. This strategy is infeasible for large stands of non-native Phragmites, and takes significant time and energy even on small stands.
Roll it flat/Crush it
- Pros: This technique is used to allow easier access to spray non-native Phragmites at a later time. Flattening the stems before burning can also help maintain safe flame and smoke conditions. Even without burning, laying the stems flat will allow for easier herbicide treatments in future seasons. (See the PDF from Janice Gilbert’s webinar on managing non-native Phragmites in Ontario for more details).
- Cons: If flattened regularly, stems build up over time and block the sunlight from reaching the soil resulting in reduced germination of other desirable plants. This option also does not remove any biomass from the site. Dried out fallen stems and leaves may also become a fire hazard.
- Pros: One of the more environmentally friendly options, however it is not currently recommended by any organization.
- Cons: Composting is not recommended for non-native Phragmites, as the seeds and rhizomes may be capable of surviving all but the hottest of compost piles. Segments of these non-native plants (stems, rhizomes, seeds) that are not completely composted before being spread on fields might only help this aggressive non-native plant spread. There are a few resources online addressing composting invasive plant species (Compost With Care, Composting Concerns).
The use of non-native Phragmites as a bioenergy product is being explored as a sustainable option for managing the overabundance of non-native Phragmites biomass produced in North America. There are many forms of potential bioenergy products including biogas, char, ethanol, pellets, etc. (Check out a great video on using non-native Phragmites for bioenergy production)
The University of New Hampshire Cooperative Extension also put together a document that explores options to dispose of invasive plant species properly, including non-native Phragmites.