You're probably familiar with some of Iowa's most invasive species and have even helped to remove or control them. Buckthorn is a problem in several areas of Ames, including the Pohl Memorial State Preserve (a.k.a High School Prairie), and honeysuckle is nearly everywhere!
But there are a couple lesser-known invasives that are uniquely suited to riparian corridors, to our floodways and floodplains. And guess what? We have both on the South Skunk.
Japanese Knotweed:
In a 2016 ISU Extension news article, Another one bites the dust, or, City of Ames beats Japanese knotweed, Dr. Bob Hartzler (ISU professor of agronomy) describes a colony of knotweed that had once grown next to the footbridge at Carr Park. Bob writes that he reported it to the city sometime around 2001, but there was still a very large and healthy colony when it was reported again in 2011 - and when reported a third time in 2014!
Loren Lown (Natural Resource Specialist at Polk County Conservation, retired) battled Knotweed at Chichaqua Bottoms for years "with limited success." Others are attempting to eradicate it along Paint Creek in Allamakee County (you can see on their map how it spreads downstream) and there are large colonies along the bank of the Des Moines River in Des Moines, on the Middle Raccoon in Dallas County and on the Upper Iowa River in Winnishiek County.
Knotweed rhizomes can grow up to 6-9 ft deep and are known to spread laterally 60 ft (as they did at Carr). They can survive for years with little or no top growth, and new stands are established when rhizomes (or even stem nodes, apparently) break off (imagine eroding streambanks) and are transported downstream.
The stand at Carr Park has been reduced largely through the efforts of a volunteer who cut and treated new growth weekly every summer for several years. But you can still find knotweed at that location, and you can't miss a new colony downstream at East Lincoln Way (north side). If not aggressively treated, it will spread downstream!
Japanese Knotweed:
In a 2016 ISU Extension news article, Another one bites the dust, or, City of Ames beats Japanese knotweed, Dr. Bob Hartzler (ISU professor of agronomy) describes a colony of knotweed that had once grown next to the footbridge at Carr Park. Bob writes that he reported it to the city sometime around 2001, but there was still a very large and healthy colony when it was reported again in 2011 - and when reported a third time in 2014!
Loren Lown (Natural Resource Specialist at Polk County Conservation, retired) battled Knotweed at Chichaqua Bottoms for years "with limited success." Others are attempting to eradicate it along Paint Creek in Allamakee County (you can see on their map how it spreads downstream) and there are large colonies along the bank of the Des Moines River in Des Moines, on the Middle Raccoon in Dallas County and on the Upper Iowa River in Winnishiek County.
Knotweed rhizomes can grow up to 6-9 ft deep and are known to spread laterally 60 ft (as they did at Carr). They can survive for years with little or no top growth, and new stands are established when rhizomes (or even stem nodes, apparently) break off (imagine eroding streambanks) and are transported downstream.
The stand at Carr Park has been reduced largely through the efforts of a volunteer who cut and treated new growth weekly every summer for several years. But you can still find knotweed at that location, and you can't miss a new colony downstream at East Lincoln Way (north side). If not aggressively treated, it will spread downstream!
Photo: Japanese Knotweed on the Skunk at East Lincoln Way (July 2020)
Japanese Hops:
In October 2014 few of the Skunks volunteered to help remove Japanese Hops from the banks of West Indian Creek at Robison Wildlife Acres (SE Story County). It's known to be on West Indian as far upstream as Nevada, but we weren't aware of it being on the Skunk until a couple years ago when two Story County Conservation Naturalists noticed it near Ken Maril Road. And it has since been found north of Ames, a bit downstream of the Anderson Access.
In October 2014 few of the Skunks volunteered to help remove Japanese Hops from the banks of West Indian Creek at Robison Wildlife Acres (SE Story County). It's known to be on West Indian as far upstream as Nevada, but we weren't aware of it being on the Skunk until a couple years ago when two Story County Conservation Naturalists noticed it near Ken Maril Road. And it has since been found north of Ames, a bit downstream of the Anderson Access.
The tiny seeds of Japanese Hops are dispersed by wind and water, and can remain viable in the soil for several years.
So please Be On the Look Out (BOLO) for these two invasive species. We'll want to stop them if we can, before they begin to take over as they have on other streams.
So please Be On the Look Out (BOLO) for these two invasive species. We'll want to stop them if we can, before they begin to take over as they have on other streams.
Photo: Japanese Hops below the Anderson Access
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