The Fight Against Phragmites

The fight against invasive plants is a difficult one, as a matter of fact, it is a battle you shouldn't necessarily expect to win.

Removing invasive plants is not an easy enterprise, especially when it has to be done in a wetland, a rather muddy, wet and messy habitat to deal with. Our first Phragmites removal project started in 2010, and even though we made great strides for a couple of years, the effort fell apart when we left the site unattended for a growing season due to lack of funding, and, we were also busy with other ventures. One growing season, then another growing season… and then, you guessed it! Phragmites took over again. Ironically, Phragmites had previously encroached upon the same site after a previous wetland revegetation effort (which we still don’t know who did) was left unmaintained and the Phragmites literally took the whole site over. So, Phragmites = 2, people = ZERO. Ouch!!

This really comes to show the importance of follow up when it comes to invasive plant management projects. Everybody wants to do invasive plant removal, with good intentions, but poor long term planning is unfortunately the norm and not the exception when it comes to fighting invasives. A lot of invasive plant removal efforts don’t achieve much, goals are poorly established, projects are not monitored. It seems that a lot of folks are removing invasives just for the sake of removing invasives without clear ecosystem restoration goals.  

Watching native plants come back after an invasive plant removal is why we do this hard work in the river's wetlands! In the picture you can see cattails, Duck potato and a sedge growing between dead Phragmites biomass. 

The fight against invasive plants is a difficult one, as a matter of fact, it is a battle you shouldn't necessarily expect to win. In the last decade or so we have undertook a number of other invasive plant projects targeting as much as two dozen other invasive plant species, here’s what we have learned when it comes to removing invasives:

  • Prioritize on one or a few highly invasive species: we all have a blacklist of invasive plants we hate and want to nuke, but you shouldn’t bite more than you can chew! These plant species have become invasive for good reasons, they are biologically very successful organisms, they are highly adaptable, they reproduce a lot, they tolerate a wide range of soil types (including our nasty urban soils!) and microhabitat conditions; they don’t have a lot of natural enemies, among many other reasons. Therefore, removing even just one species is in itself an uphill battle, so, pick your battles! Assess the species at your site and use the national I-Rank system developed by NatureServe, it will help you make your decisions. Is the target species listed as an early detection species? Is it patchy and scarce or overabundant? What natural resources is it affecting? What functions or ecosystem services do you want to restore by removing the species? What native plant species/communities do you intend to establish at the site?    
  • Choose one site and focus on it: it's all about quality over quantity, plus, few organizations have enough money to effectively cover many sites when it comes to invasive plant management. Choose one site, determine your restoration goals and focus on it. Have a list of native plants you want to propagate once removal efforts are satisfactory. Most importantly, choose a site that is manageable for your budget, you don’t want to take a 20-acre Phragmites jungle with a 2 people crew!
  • Be consistent: invasive plant removal takes several years, a lot of people say five years at least. If you have worked controlling invasives for more than five years, you know it takes more than that. Work diligently every growing season for several years. It is better to deal with smaller patchy regrowth than leaving the site unattended for one or two years and then having to come back later and deal with an awakened sleeping giant! (don’t learn the hard way like we did!).
  • Use all the removal techniques at your disposal: three words Integrated Pest Management (IPM). When planning your invasive plant control effort, think IPM. The IPM approach entails utilizing all the appropriate pest management strategies available, endeavouring to make a sensible use of pesticides, when needed. Too many invasive plant removal efforts out there are way too “addicted” to herbicides and they forget that the target plants can become ‘superweeds’ and that pesticides have their own drawbacks, they do have other environmental impacts and they pose occupational health hazards. Use chemical control techniques rationally and try to use different non-chemical removal techniques as part of the “attack plan”.

The Gateway wetlands Phragmites removal project has been one of our biggest success stories when it comes to removing invasives. The site is located in northeast DC and is part of Anacostia Park and the National Capital Parks-East (National Park Service). We started removing the invasive grass in the fall of 2014 with a herbicide treatment (foliar applications) using Rodeo. Then, during the winter, we cut down the dead reeds using brush cutters. For that we contracted our friends from Environmental Quality Resources. What popped up in the following growing season was astonishing. A lot of native plants, presumably from the soil’s seed bank resurged from the dead Phragmites mess. Species like Soft Rush, Woolgrass, Fireweed and Rusty Flat Sedge came a remarkable resurgence and the Phragmites regrowth was surprisingly low and manageable. The invasive plant removal warrior’s paradise!

The Gateway wetlands site in 2014 (left picture) prior to the invasive plant removal efforts and 2016 (right picture) after the ongoing removal efforts. 

We have been monitoring the vegetation at the site since the pre-removal phase. In September of 2014, prior to the initial Phragmites removal actions the average Phragmites cover class was 5 (51% to 75% Phragmites cover). This was recorded using randomly placed 1 m x 2 m plots. Almost two years later, in August of 2016, the average Phragmites cover class was down to 1 (1% to 5% Phragmites cover). On the other hand, the non-Phragmites cover, which includes any other plant that is not Phragmites went up inversely from an average cover class of 1 to cover class 5! However, this non-Phragmites cover included invasive species like Mile-a-minute and Purple loosestrife, especially for the plots on the eastern portion of the wetland.

The same monitoring plot before (2014) and after (2016). The site was subject to a herbicide application and then the dead Phragmites reeds were mowed to allow faster organic matter decomposition and more efficient sunlight penetration on the soil to foster native plant germination. The native plants in the after photo are mostly Rusty flat sdges and Fireweed. 

As of last year (2016) we estimated the total area of Phragmites regrowth to be of only  between 2-3 acres. From being an 8-acre Phragmites ‘jungle’ to 2-3 acres of patchy growth, that’s over 60% reduction in the area covered by Phragmites! We have been removing Phragmites consistently for the last three years at the site, we can say that persistence has paid off so far.

We love to see wildlife using our restored habitats like this nice Great Blue Heron! Note the dead Phragmites stumps and the healthy rushes thriving at the edge of this pond at the Gateway wetlands. 



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