by Michelle Delepine, invasive program coordinator and conservationist
Each year our early detection, rapid response (EDRR) program conducts outreach and expands the geographic area surveyed for priority invasive weeds. This past year (July 2024 – June 2025) we surveyed about 4,000 acres of private land and shorelines. Our surveys were conducted on private properties as well as along the shores of the Multnomah Channel and in the Linnton neighborhood of northwest Portland. We also partnered with Scappoose Bay Watershedwatershed an area of land that channels rainfall, snowmelt, and runoff into a common body of water, such as a nearby lake or river. Multiple streams can be part of the same watershed area, such as the Tryon Creek Watershed which is fed by Oak Creek, Park Creek, Falling Creek, and others. Council to continue surveying the entirety of Scappoose Bay from the water. On private property, our top priority weeds were garlic mustard, knotweed, and spurge laurel. Along shorelines, we looked for aquatic weeds such as common reed, water primrose, and purple loosestrife.
This map shows all of the patches of EDRR weeds that our staff treated in 2024-2025. Bigger circles signify larger patches. The key shows how many total patches of each type of plant were treated.
We found sixteen different priority species from our EDRR list (see Figure 1.). Not all of these species were controlled (controlling by means of manual removal or herbicide application) throughout our district . Lesser celandine, for instance, is considered an “EDRR species” on Sauvie Island, but generally not elsewhere in our district. The table below (Figure 1.) lists the weed species we found and controlled during our surveys. In all, we found just 8.9 acres of weeds. While this is a low number in comparison to the acreage we surveyed, it isn’t too surprising since we are only targeting weeds that are not yet abundant on the landscape, in order to keep them from becoming too abundant and impossible to control.
Figure 1. EDRR Species Found (July 2024 – June 2025)
| Name of Weed | # of Patches | Total Size of Patches (sq ft) |
| Garlic mustard | 1805 | 157,170 |
| Knotweed | 131 | 35,603 |
| Lesser celandine | 69 | 32,216 |
| Purple loosestrife | 31 | 79,685 |
| Pokeweed | 17 | 6,109 |
| Wild chervil | 13 | 6,175 |
| Phragmites | 13 | 16,755 |
| Spurge laurel | 94 | 49,670 |
| Indigo bush | 5 | 800 |
| Ludwigia spp | 8 | 385 |
| Oblong spurge | 13 | 513 |
| False brome | 3 | 17,50 |
| Orange hawkweed | 26 | 1,817 |
Our top EDRR weed species include the seven species listed in Figure 2. below. Garlic mustard is one of our most targeted species. While we found 1,805 individual patches of garlic mustard, we also returned to 1,580 patch locations that previously had garlic mustard and found none! Some 99 properties that used to have several infested patches now have none at all. That is due to the continued success of our previous control measures, which in some cases exceeds over 15 years of work! This year was notable for observing far less garlic mustard overall on the landscape than in years previous. Garlic mustard seed is thought to be viable for 12-15 years, so it makes sense that our years of dedicated work are starting to make a noticeable difference across our District.
We were excited to be approached for a news story about our work on garlic mustard control, which featured Michelle Delepine. The segment aired on Portland’s KGW TV station on May 6.
Additionally, we controlled 131 patches of knotweed and 13 patches of common reed (phragmites australis ssp. australis). In the coming year we will continue to look for and control priority weeds found in our EDRR list.
Figure 2. Total area of priority weed species controlled for our top target weeds
Special thanks to the Oregon State Weed Board (OSWB) grant program which partially funds our garlic mustard effort, along with the efforts of several land stewardship partners across the Portland area. We were awarded $57,551 in funding from the OSWB grant program to support this ongoing, important work in 2024-2025 to contain and decrease the presence of garlic mustard in Portland to prevent the spread of garlic mustard to areas outside the Metro area.