Garlic Mustard, Alliaria petiolata, is a prevalent invasive species in the watershed with alarming impacts on other plants. This weed is known to be allelopathic. The garlic mustard roots produce chemicals that are toxic to other plants, which aids its rapid spread. This can prevent the establishment of other plants and allows garlic mustard to completely dominate the understory.
Johnson Creek Watershed Council has been combating this weed since 2009 and continues every year to remove it from the watershed. Recently, JCWC has been the only organization in Portland solely hand pulling the weed.
Now, 11 years later, we are seeing a huge decline in its numbers from repeatedly removing it.
The map and chart show garlic mustard infestations aggregated by stream reach; most of the data are from private property, not including public spaces managed by government agencies. These areas are dropping drastically in numbers: One reach had over 1000 square meters infested in 2010 and it dropped below 50 square meters in 2020. That is a twentieth of its original infestation! 8 out of 9 reaches saw a decrease in garlic mustard since 2010 and all of those decreased to at least a tenth of their original infestation.
Garlic mustard can spread quickly by seed when the creek carries it downstream; so it is paramount that garlic mustard is not left unchecked and that JCWC continues this work along its riparian areas.
We want to give a big shout to all of our interns that have helped the council remove garlic mustard from the watershed. This has been a huge effort and we are extremely grateful for your work!
In 2016 interns pulled garlic mustard for 172 hours, in 2017 for 233.25 hours, in 2018 for 166.75 hours, in 2019 for 184 hours, and in 2020 for a whopping 285.5 hours. This is a grand total of 1041.5 hours from dedicated interns!
So much time, effort, and passion have been put into this project and we wouldn’t see the numbers we have today without you. Thank you!
In total, 52.13 acres of land (or 39.49 football fields) have been surveyed for garlic mustard and 4.67 acres (3.53 football fields) of pure garlic mustard have been removed along Johnson Creek’s riparian zones from 2009 to 2020.
This work couldn’t have been done without Noah Jenkins, JCWC’s Riparian Program Manager, who started this project in 2009 and has put in thousands of hours reducing this weed. Thank you so much for your commitment to the JC watershed and your dedication to this work!