Salem Maritime National Historic Site
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  • Taking Care

    Common Invasive Plants

    • Purple loosestrife (Lythrum salicaria)
    • Multiflora rose (Rosa multiflora)
    • Chinese bittersweet (Celastrus orbiculatus)
    • Common reed (Phragmites australis)
    • Burdock (Arctium)
    • Curly dock (Rumex crispus)
    • Japanese knotweed (Reynoutria japonica)
    • Garlic mustard (Alliaria petiolata)

    *This is not a complete list, only a list of common invasive plants at Saugus Iron Works.

    Image Descriptions

    1. Biological Science Technician, L Yates, removes multiflora rose at the beginning of the Nature Trail.
    2. Biological Science Technician, J Lampley, treats the common reed with a tropical herbicide, using the cut and stump treatment, in the Saugus River.
    3. Common invasive species at Saugus Iron Works include: purple loosestrife (Lythrum salicaria), multiflora rose (Rosa multiflora), and Chinese bittersweet (Celastrus orbiculatus).
    4. Common native species at Saugus Iron Works include: goldenrod (Solidago spp.), cattails (Typha angustifolia), and joe pye weed (Eupatorium purpureum)


    Overstory: the upper canopy portion of a forest, made up of trees' upper branches.

    Understory: the portion of a forest's vegetation that is close to the ground.

    Herbicide: a substance used to kill or stop the growth of a targeted plant.

    Audio Transcript

    Saugus Iron Works became a National Park Service site in 1968. For many years, across the national parks, ecosystems were left alone to maintain themselves.  So when the invasive Norway maple, along with several other nonnative plant species, began to establish along the Nature Trail, the National Park Service left the ecosystem alone to take care of itself, because no one understood that the ecosystem didn’t have the tools to combat a problem humans had created. Eventually, scientific knowledge advanced. In the year 2000, the National Park Service launched a multi-year action plan called, “The Natural Resource Challenge.” One of the key initiatives focused on invasive species management.  

    Norway maples slowly began to be removed from the Nature Trail. As the tree canopy began to open, there was more room for native species. But, this also meant more sunlight for other invasive species, like multiflora rose, that thrived closer to the ground, in the understudy.  

    Now that the National Park Service understood how damaging invasive species were to the ecosystem, the agency had to learn how to remove them.  

    The obvious answer is to cut invasive plants. But then they can just grow back. Another solution is to spray herbicides that kill plant roots, so they can't grow back. But it’s hard to use this method without spraying and killing native plant species too. 


    Today at Saugus Iron Works, Biological Science Technicians use a combination of these two methods - the cut and stump treatment. They cut back plants and then apply a little bit of herbicide to the stem or stump, so the invasive plant won't grow any further.  

    As you travel down the Nature Trail, you may come across natural resource management staff, who continue to look after the wetlands and forest, and treat invasive plants. The goal is not to kill plants, but to restore a native dominant habitat that can support biodiversity and complex food chains. The Nature Trail used to be a monoculture of Norway maples. They still pop up sometimes, but the forest is now mostly composed of native species like the shagbark hickory. 


    And across the National Park Service, managing invasive species has become one of the most important ways of reducing human impact on the environment.