We're being invaded by these common invasive species at our wetland sites!
In September, we will be heading out to our monitoring sites once again to look for those dreaded invasive, non-native plants! In preparation for our invasive species mapping, this Plant of the Month Blog is a 3 for 1, looking at some of the most prevalent invasives we see at our monitoring sites!
Why should you care about invasive, non-native species?
Invasive, non-native species are those that evolved in another part of the world but are introduced into a new habitat and able to reproduce, grow quickly and often disrupt native ecosystems. They are frequently introduced as ornamental plants in gardens or accidentally through the global movement of people and goods. Not all non-native species pose a risk to our native ecosystems, but invasives can displace native species by outcompeting them for resources, by parasitizing natives, or by choking them out. This can be especially problematic if the non-natives do not provide the same level of functionality to the rest of the ecosystem, such as food and habitat for wildlife. Some invasives will also form a monoculture, reducing biodiversity in the ecosystem and making ecosystems less resilient to change.
Threat levels
The North Carolina Native Plant Society ranks invasive, non-native species with various threat levels based on how likely they are to displace our native plants. Their three rank system is outlined below. All of the invasives that we will look at in this blog are Rank 1: Severe Threat species! In the field we will look for Rank 1 and Rank 2 species.
Rank 1: Severe Threat
“Exotic plant species that have invasive characteristics and spread readily into native plant communities, displacing native vegetation.”
Rank 2: Significant Threat
“Exotic plant species that display some invasive characteristics, but do not appear to present as great a threat to native communities in NC as the species listed in Rank 1.”
Rank 3: Lesser Threat
“Exotic plant species that spread into or around disturbed areas and are presently considered a low threat to native plant communities in NC.”
Japanese stilt grass (Microstegium vimineum)
Japanese stilt grass grows in moist soils and can carpet floodplain wetland sites, with its bright green stems. It can grow up to 2-3 feet tall. Its leaves are lance shaped and have a shiny, silvery, off-center midrib. Its leaf blades can be hairy on both sides. Stems are weak and have distinct non-hairy nodes or joints. Although normally bright green, it turns tan in fall and winter.
Photo credit: Cory Burt
Watch out! It might be confused with white grass (Leersia virginica), which it often grows alongside. However, white grass has hairy nodes and no shiny mid-rib.
Japanese stilt grass may have been introduced as packing material used for shipping from Asia. This grass can grow thickly and shade out other native species. Its many seeds can spread quickly by wind or flood waters. Unlike many other plants, it is not readily browsed by deer. All these factors lead to a very problematic invasive!
Japanese honeysuckle (Lonicera japonica)
Many people have fond memories of honeysuckle plants... the sweet aroma of its flowers and the sweet taste of nectar sucked out of the flowers during the summertime.
However, Japanese honeysuckle can be highly invasive, outcompeting native plants and girdling young trees.
Japanese honeysuckle was brought over from Asia as an ornamental plant and is still sold and planted in gardens for ornamental value or planted for the browsing of horses. Unfortunately, once planted, this species can quickly spread both by seed and via their root systems. Once it spreads, it can outcompete native plants for nutrients and grow up small trees, blocking out sunlight for the trees and plants below. It will grow in disturbed areas, such as floodplains, which may be one of the reasons we see it at our sites.
When you can’t smell its white and yellow flowers, Japanese honeysuckle can be identified by it’s small (1-2.5 inch), oval, entire (smooth), green, opposite leaves with pale undersides. Younger leaves, may lobe.
The leaves grow along a thin, hairy, reddish to brown vine. The vine can grow along the ground or vertically up small trees. On older plants, the vine can get up to 2 inches in diameter and develop a splintery quality.
In fall it fruits with small, black berries.
Photo By: Paul Winn
Photo By: Will Bennett
Photo By: David Jeffrey Ringer
We also have native honeysuckles that can be distinguished by some of their leaves being fused, rather than separate. They also have reddish fruits and hairless stems.
Japanese honeysuckle can also be confused with yellow jessamine (Gelsemium sempervirens), which has thinner, longer, shiny leaves, and hairless stems.
Chinese privet (Ligustrum sinense)
Chinese privet was originally used in landscaping. However, it has also become an aggressive and far-reaching invasive.
It can be a small to large shrub and it does particularly well in floodplains, due to its affinity for moist soils and few native shrubs to compete with. However, it can quickly grow into dense thickets that outcompete natives and block sunlight from other plants. It spreads by both root and seed. Its small, dark purple drupes are popular among birds who spread its seeds quickly.
Similarly to Japanese honeysuckle, Chinese privet has small, entire (smooth), oval, opposite, green leaves. However, leaves tend to be smaller and shinier than honeysuckle. This plant also grows as a many-stemmed, bushy shrub, not a vine. It has small white flowers and is frequently evergreen in North Carolina. It has smooth tan/grey bark.
Photo By: Annabelle Corboy
While many invasive species are difficult to combat and there is debate about what their role should be in an ever-changing world, identifying where they are and trying to control or stop their spread can be very important in protecting our wetland resources.
Where can I learn more?
NC Native Plant Society Non-native Invasive list: https://ncwildflower.org/invasive-exotic-species-list/
NCDOT Invasive Exotic Plant Guide: https://connect.ncdot.gov/resources/Environmental/Compliance%20Guides%20and%20Procedures/Invasive_Exotic_Plants_Manual_May_2012.pdf
A field guide for the identification of invasive plants in southern forests: https://www.fs.usda.gov/research/treesearch/35292
Mistaken Identity? Invasive plants and their native look alikes: https://www.nybg.org/files/scientists/rnaczi/Mistaken_Identity_Final.pdf
