Invasive Plants

Oak smothered and broken by Oriental bittersweet

Invasive plants earn their label by growing and reproducing faster than native species in the same growing conditions. Free from the predators, diseases, and other plants that keep them in check in their native ranges, they monopolize the light, water, and other nutrients all plants need. Sometimes these dense colonies even alter the air temperature and soil chemistry around them, further squeezing out other plants and the animals that depend on them.

(Definition by the Massachusetts Invasive Plant Advisory Group, quoted by the Native Plant Trust)

Invasive plants are a huge threat to biodiversity and sustainable ecosystems. Steps you can take to control them.

Know Invasive Plants

Fortunately, there are relatively few plant species that are causing the most damage. Below is a list of the most egregious thugs. The Rhode Island Invasive Species Council  lead by the Rhode Island Natural History Survey has compiled the most official full list organized by type of plant for 2020.

The information below comes from the Center for Invasive Species and Ecosystem Health. It has posted most of the plants on RINHS list with links to a wealth of information and large sized images of each of the plants including  information about removing them. The Center for Invasive Species and Ecosystems is invaluable, offering  comprehensive information about thousands of invasive plants, insects, pathogens and other species.

(Note: There are some native plants that are aggressive and can spread easily. While they are not recommended for small areas, they are not considered invasive because they do not usurp the ecological functions of other native plants.)

Prefer a downloadable pamphlet with some of the most invasive species? See Invasive Plants: The Threat They Pose from Friends of Canonchet Farm

Trees/ Shrubs

Herbaceous Plants

Vines

If you see a plant that is super aggressive figure out what it is. (Apps such as iNaturalist make it easy to identify plants.) Consider joining a volunteer effort, such as those of your local land trusts, to combat invasives on public land. You can learn how to remove them, and meet others who share an interest in habitat restoration.

Don’t Grow Invasives

You might find that you have some of these invasives in your yard. You may have even planted some. That is understandable. When these plants were first brought to this area many were grown for their hardiness and ability to grow quickly. But these plants in particular are very aggressive and take over either in the area where they are planted or the seeds are spread by birds and these plants come to  overpopulate our larger landscapes. 

Don’t plant them, divide them or give them to friends. (Rhode Island is one of the few states that does not restrict the sale of invasive plants so some of these such as barberry, multifora rose and burning bush are available and promoted for sale.) 

Control Invasives

Be vigilant. The best time to control invasive plants is when the are just getting started. If you see a new plant on property you maintain and know it is an invasive, remove it as soon as possible. Once established they are much harder to control. The Native Plant Trust has recommendations for how to remove common invasives.

The most ecologically sound method is preventing new growth by pulling them out and removing all growth above the ground. Since all plants survive by photosynthesis, they will eventually starve with repeated removal of all the above ground portion of the plant.  Other methods include, depriving the plant of light or using the sun to super heat the soil (solarizing).  Herbicides should always be used as a last resort as they can and do cause environmental harm. Also make sure to dispose of the plant waste in a way that does not allow them to spread. Ideally this waste should be burned or composted at high heat to kill the plant entirely. 

Replace Invasives with Natives

Once you remove the plants you need to replant or the invasives are likely to come right back. Any disturbed uncovered soil is a magnet for invasives. The Native Plant Trust has a brochure suggesting specific native plants of New England  to use in place of their invasive counterparts.  Find the native plants that are most appropriate for your growing conditions. 

Native Plant Trust Garden Plant Finder is comprehensive and regularly updated. Plants can be searched by ecoregion, types, growing conditions, a host of plant characteristics including specific its specific ecological value. Images of plants are very helpful. When searching we urge you to select plants native to our ecoregion (Northeast Coastal Zone) and species vs. cultivars or specimen in order to maximize the ecological contribution of the plant to your landscape. 

URI, RI Native Plant Guide focuses on a subset of the 1,300 species listed in 1998 edition of Vascular Flora of Rhode Island. Selected for their ornamental value, potential in restoration projects and ease of propagation plants can be searched by type, characteristics, ecological value as well as growing conditions.