Invasive Arum - Ask Extension
Hello, I have the dreaded invasive Italian Arum. I've tried to dig it out over the last couple years - disposing of rootlets, bulbs, and surrounding s...
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Invasive Arum #823674
Asked March 27, 2023, 10:58 PM EDT
Hello, I have the dreaded invasive Italian Arum. I've tried to dig it out over the last couple years - disposing of rootlets, bulbs, and surrounding soil - but despite my efforts it's coming back year after year and continuing to spread. I never use chemicals to control weeds but the extreme invasiveness of the arum is making me consider an exception to this rule... I would love to hear any strategies you have to eradicate this plant. Boiling water, blowtorch, less toxic/highly targeted herbicide...? Thanks in advance for any ideas!
Multnomah County Oregon
Expert Response
Abigail: Arum is a very difficult plant to get free of as you have already noticed. Between root pieces, seed from the berries, and small tubers, it is considered one of the most challenging garden weeds to completely eliminate. My sense is that you may have inherited quite a reserve of seed and vegetative pieces.
I could find nothing on the efficacy of 20% vinegar (not the 5% in the grocery store) on arum which can be purchased at garden centers but I am not sure that it would have a significant impact on the below ground plant pieces. The soil can be a tremendous buffer and in reacting to the acetic acid in vinegar, denature it fairly quickly. But it might be worth a try to compare it with other treatments. Just mark the places you have done it and see the impact a year later.
The herbicide that is most effective (and also available to home gardeners) is probably glyphosate (Roundup and other trade names). Leaf application is challenging since the leaf is so waxy. A fine spray that doesn't run off the leaf works best. But with a fine spray, you need to make sure it isn't drifting onto plants you care about. It can be tricky. I have worked with several people that have cut the leaves from the stems and then painted or sprayed the cut surfaces of the stems. They felt that was more effective. But, that is also a challenging project.
As with the vinegar, mark the area that you used glyphosate and check it for a year after application to see how well it did.
With herbicides, including the herbicidal vinegar, read and follow the label instructions and personal safety concerns.
The other is the infamous carbohydrate starvation technique which requires a stern focus and a gleam in your eye that guides you almost daily to all the new leaves that has emerged and that you will remove promptly. It means no summer vacations and lots of very time wearing the plants out. It does get easier as you keep them from capturing sunlight to make carbohydrates for their future survival. This has worked on some very tough weeds but have yet to have someone really try it with arum.
Hope this helps. Feel free to call or email me directly if you have questions. Chip Bubl OSU Extension Agent/Columbia County <personal data hidden> or <personal data hidden>
I could find nothing on the efficacy of 20% vinegar (not the 5% in the grocery store) on arum which can be purchased at garden centers but I am not sure that it would have a significant impact on the below ground plant pieces. The soil can be a tremendous buffer and in reacting to the acetic acid in vinegar, denature it fairly quickly. But it might be worth a try to compare it with other treatments. Just mark the places you have done it and see the impact a year later.
The herbicide that is most effective (and also available to home gardeners) is probably glyphosate (Roundup and other trade names). Leaf application is challenging since the leaf is so waxy. A fine spray that doesn't run off the leaf works best. But with a fine spray, you need to make sure it isn't drifting onto plants you care about. It can be tricky. I have worked with several people that have cut the leaves from the stems and then painted or sprayed the cut surfaces of the stems. They felt that was more effective. But, that is also a challenging project.
As with the vinegar, mark the area that you used glyphosate and check it for a year after application to see how well it did.
With herbicides, including the herbicidal vinegar, read and follow the label instructions and personal safety concerns.
The other is the infamous carbohydrate starvation technique which requires a stern focus and a gleam in your eye that guides you almost daily to all the new leaves that has emerged and that you will remove promptly. It means no summer vacations and lots of very time wearing the plants out. It does get easier as you keep them from capturing sunlight to make carbohydrates for their future survival. This has worked on some very tough weeds but have yet to have someone really try it with arum.
Hope this helps. Feel free to call or email me directly if you have questions. Chip Bubl OSU Extension Agent/Columbia County <personal data hidden> or <personal data hidden>
