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Invasive Species at Whiterock Conservancy




Land management efforts at Whiterock Conservancy supports a multitude of ecosystems and sensitive species across its 5,500 acres. However, many invasive species found throughout Whiterock have also made their home here, threatening efforts to restore native ecosystems. Whiterock’s Experiential Learning Coordinator, Susan Hill, recently sat down with the Director of Land Stewardship, Carissa Shoemaker, to learn about the Conservancy’s approach on invasive species.



Leafy green bush with white flowers
Honeysuckle

“We have had different invasive pressures throughout the years, but I think the biggest threat to Whiterock’s native plant communities right now are the noxious woodies, including bush honeysuckle and multiflora rose, but especially honeysuckle,” says Carissa. Honeysuckle is invading both the woodlands and prairies of Whiterock. It’s very difficult to eradicate as it spreads easily and has a long growing season. As one of the first plants to leaf out in the spring, honeysuckle shades out native plant species before they have the chance to grow. Honeysuckle is also one of the last plants to lose its leaves in the fall. This extended growing season allows it to grow larger and outcompete natives. “When it’s young, we can clear it with fire, which is a really efficient tool that encourages native plants and suppresses invasives,” Carissa notes. However, once honeysuckle reaches a certain size it becomes more resistant to fire. Manual removal, goat browsing, and herbicides can also be used to fight honeysuckle infestation.


line of fire along the edge of a woodland
Prescribed Burn

Invasive species often thrive in areas of disturbance, such as highly trafficked areas, erosion-prone hillsides, or even zones of ecological restoration. There are several areas at Whiterock where red cedars were removed in order to allow more prairie species to grow (although native, red cedars are very aggressive and can colonize large areas, shading out native species). “Once we did that, honeysuckle shot up in its place, capitalizing on the open canopy and disturbance from the clear cutting,” Carissa explained. “Instead of all these natives growing up from the seed bank, we had honeysuckle grow up.” That area remains one of the worst infestations on the property.


Another invasive at Whiterock is reed canary grass. Reed canary invades wetlands and floodplains, including Whiterock’s remnant seeps along the Middle Raccoon River. However, we currently do not focus on reed canary as much as the woody invasives. There is a very narrow timeframe in which reed canary can be burned. If you burn too early in the spring season, the reed canary likely has not greened enough for the fire to have an impact on growth, burn too late in the season and you risk harming ground-nesting birds and endangered Blanding’s turtles. Prescribed (RX) Fires are the main practice used to remove reed canary at Whiterock, but new research could change the way reed canary is managed. “We have heard good things about new herbicide mixes for reed canary and the potential for natives that are parasitic to reed canary, like swamp betony, to loosen its grip, which is really exciting,” Carissa shares. She hopes to test different methods of invasive species removal here at Whiterock, since there are so many approaches that can be put to practice.



Other invasive species, like oriental bittersweet, black locust, Japanese barberry, buckthorn, autumn olive, tree of heaven, and Sericea lespedeza have only been spotted in a few occurrences, and are not well documented. “We can use citizen science to get a better idea of where some of the other invasives are located,” suggested Carissa. “We are bound to have some of them across these 5,500 dynamic acres.” The use of citizen science tools, such as iNaturalist, to document locations of these additional invasive species could help inform the land management team on where to focus future efforts and research. Help support Whiterock in fighting invasive species by recording locations on our iNaturalist page, or become a land management volunteer.



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