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Invasive Plant Management

What is the invasive plant strike team and why/when did Cleveland Metroparks create it?

The invasive plant strike team was created as part of the Invasive Plant Management Program (IPMP) in early 2009. The project was designed to expand the ongoing invasive plant removal work done by the Natural Resource Managers at Cleveland Metroparks. The goal of this six-year capital project is to protect the biological heritage of the Park District by preventing the establishment and spread of invasive plants. This team of seasonal employees is trained to identify target plant species, use herbicides and application equipment safely, keep accurate records for daily treatments, maintain the Weed Information Management System data base (WIMS), and map the location of invasive species.

How and where does the invasive plant team operate? Is Cleveland Metroparks the only park with an invasive plant strike team?

Bags of garlic mustard (Alliaria petiolata)
pulled from areas in Cleveland Meteroparks await disposal.

The invasive plant strike team typically works in targeted areas where native plant biodiversity is most threatened by invasive plants. The team is very selective about how it removes the invasive plants and does so in a way that is safest to adjacent plant populations. Contractors applying herbicides typically work in monoculture areas where invasive plant populations comprise over 80% of the total plant population.

Across Cleveland Metroparks and other park systems, area managers have been removing invasive plants for many years. Each park system has its own unique challenges and solutions with invasive plants and formulates invasive plant teams accordingly. Cleveland Metroparks created the invasive plant strike team in order to centralize knowledge and coordinate priorities for dealing with invasive plants in our park system.

What are invasive plants? How did they get here? Do they look like native plants? How can I tell an invasive plant from a native plant?

One of these pretty wildflowers is an invasive plant species. Read the paragraph below to find out which one.

   
wild hyacinth (Camassia scilloides wild geranium (Geranium maculatum)  

 Dame’s-rocket (Hesperis matronalis)

Non-native (or exotic) plants are species that are introduced to an area where they do not, or historically have not, occurred naturally. Some exotic plants were transported by early explorers, who brought plants with them from their home countries to serve as sources of food or fiber. The same tradition continues today as exotic plants are often introduced to an area for ornamental, soil stabilization, or other reasons. Non-native ornamental plants are bred for pest and disease resistance, fast growth, and abundant flowers or fruit. A very small fraction of non-native plants become invasive in their regions, often because they have escaped from the threats posed by insects, diseases or mammals in their native range. This imbalance can lead to a competitive advantage that allows these plants to spread aggressively. This, in turn, displaces other organisms that depend upon native plant species. Invasive plant species can severely disrupt an ecosystem’s cycles and ability to function.

There is no magical or easy way to tell an invasive plant from a native plant. Invasive plants can and often do look like native plants in appearance, contrary to what many people may expect. Can you guess which species pictured above is the invasive species? It is Dame’s-rocket, a common late spring wildflower found along roadsides, located on the far right. Be sure you don’t mistake it for a similar looking native plant with five petals, Wild blue phlox (Phlox divaricata). To see a list of invasive plants that are in Ohio, visit the Ohio Invasive Plant Council by clicking here.

What invasive plants are in Cleveland Metroparks? Which cause the most harm? (What plants we are focusing on)

   

 Lesser celandine (Ranunculus ficaria)    
  Garlic mustard (Alliaria petiolata) 

 

Unfortunately, there are many invasive plants found in Cleveland Metroparks. The 12 species that are of highest priority to the IPMP are:

Norway maple (Acer platanoides), garlic mustard (Alliaria petiolata), Japanese barberry (Berberis thunbergii), Japanese honeysuckle (Lonicera japonica), Asian bush honeysuckles (Lonicera maackii, L. morrowii, and L. tatarica), purple loosestrife (Lythrum salicaria), reed canary grass (Phalaris arundinacea), phragmites (Phragmites australis ssp. australis), Japanese knotweed (Polygonum cuspidatum), lesser celandine (Ranunculus ficaria), glossy and European buckthorn (Frangulus alnus and Rhamnus. cathartica), multiflora rose (Rosa multiflora), and narrow-leaved and hybrid cattail (Typha angustifolia and T. x glauca).

These plants have been identified as causing the most harm to the biological integrity of the Park District. What plant or plants the invasive plant strike team focuses on at any given time depends on the seasonality (phenology) of each species and when they are most susceptible to removal. Another 18 species are secondary targets, and new species may be found and added to the list as the invasive plant strike team continues to work in the field.

Can wildlife in the park adapt to coexist with invasive species?

   
Red-winged Blackbird 
(
Agelaius phoeniceus)
 A honey bee on invasive
Canada thistle (
Cirsium arvense)

Not always. Many species have a very specific niche in the ecosystem, which is the complex relationship of a species’ specialized diet, habitat, breeding strategy, and other roles that a species plays in nature in order to survive. Niches are disturbed where invasive plants have displaced native plants, which cause a reduction in species diversity. When an invasive species comes to an area, it doesn’t just take the niche of one native species. Invasive plants can out-compete multiple native species to form a monoculture, which is an area dominated by a single species. Monocultures cannot sustain plant and animal diversity the way a community of native plants, animals, and microscopic organisms can. It is important that invasive species are controlled so monocultures do not form.

Why does the Cleveland Metroparks use herbicide? Is it harmful?

   
glyphosate-treated Lesser celandine 
(
Ranunculus ficaria)
An invasive plant strike team member 
sprays herbicide on Lesser celandine

Plants that can be removed without herbicide, such as garlic mustard, are pulled by the invasive plant strike team. However, some of the well-established and widespread invasive plants in Cleveland Metroparks have extensive roots systems that make mechanical removal ineffective. Cleveland Metroparks uses glyphosate as an herbicide to remove upland and wetland plants. Toxicity levels are low for mammals, birds, and fish, and because of its water-based nature, it is readily absorbed on its target and leaches or spreads very little. Most plants are treated prior to fruiting, which decreases herbicide-treated plant consumption by other species. The invasive plant strike team is very selective about where and when herbicide is used, and it is applied in the most targeted way possible. 

   
teasel (Dipsacus sylvestris)      narrow-leaved cattail (Typha angustifolia)

Treatments near water require an herbicide registered for aquatic use. It is important to keep our wetlands healthy because they are ecosystems with high species diversity and aid in the absorption of rainwater. Wetlands are highly productive and diverse ecosystems which are vulnerable to invasion by phragmites, non-native cattails, and purple loosestrife.

What happens to all of the plants that are pulled?

The plants that are pulled are collected, recorded, and disposed of. Unfortunately, the pulled invasive plants cannot be composted at a temperature high enough to sterilize their seed. It is important to ensure invasive plant seeds do not germinate and continue spreading the species.


Dame’s-rocket and Garlic mustard
collected by the invasive plant strike team

 

What happens to areas after the invasive plants are removed?

The recovery of native plant diversity after invasive plants are removed will vary from site to site. The park will continue to take measures to minimize re-infestation. Based on the quality of the area, native plant communities may return naturally, however, some sites may require restoration using plants native to our region.

How can we keep invasive plants from coming back the next year?

Many plants are sprayed or removed just before flowering. Because plants allocate a lot of energy into producing reproductive materials, such as flowers and seeds, it is more vulnerable at this time because less energy is contributed to the plant’s normal survival functions. However, because some invasive plant species are difficult to kill, the invasive plant strike team fully expects to revisit areas to ensure these populations are minimized.


The invasive plant strike team uses the Argo, 
a vehicle used to deploy herbicide on plants difficult to reach on foot.

What progress has Cleveland Metroparks made so far? What is the future of the Invasive Plant Strike Team?

While it is not possible to completely remove all invasive species from the park, the invasive plant strike team has had success in controlling invasive plant populations in its first year. Progress can be difficult to measure precisely, without expensive and time-consuming plant community monitoring. It is the goal of the team to reduce populations of invasive plants until they can be managed sustainably with existing park resources. The team will be at the height of its work in the next couple years, as it progresses through its targeted treatment areas.


These pink flags indicate an area in the park where
invasive plants are being treated

What can I do to help?

You can spread awareness about invasive plant species to other people. Many invasive species have been transported by human activity. It is important that the invasive species in the park are not dispersed elsewhere. Purchase native plants for your home and garden and support nurseries growing these plants. Let nurseries know that some of the plants they are distributing are spreading into and threatening natural areas. Replace aggressive, invasive species such as barberry, lesser celandine, Norway maple, honeysuckle, burning bush, and English ivy with native trees, shrubs and ground covers. You can also volunteer or join invasive plant removal events that occur throughout northeast Ohio.


Crown vetch (Coronilla varia L.
Some invasive plants may be beautiful, but native plants are better suited for a garden.