How to eradicate aggresive plant

Asked March 26, 2017, 6:32 PM EDT

Hi - can you tell me what this plant is and if there is anything I can do to eradicate it and keep it from spreading. It had taken over a bed. I dug all the plants out by hand, put the plants and roots in the garbage, not the compost, and covered the worst area with weed cloth and cardboard for a season. It is re-emerging. Thanks for any ideas.

Polk County Oregon

2 Responses

Thanks for your question about your plant. I believe it is a winter caladium, which is a hardy plant that grows from an underground structure called a tuber (and erroneously called a bulb.) Under mild winter conditions such as we have in the Valley, they are perennial. They are technically not invasive, and have over 1000 cultivars. Because they are valued, I could find no eradication resources. But if they're a weed to you, then they're a weed! The only reliable way to get rid of them is to dig up every bit of tuber because, like potatoes, any part of the fleshy tissue can generate a new plant. Covering the soil won't work. You might want to consider a small tractor to remove the soil and replace it with some no-tuber containing topsoil. Good luck!

My fellow M.G., Jean Natter, has corrected my identification of your plant. It is Arum italicum, common name lords and ladies, and is listed as invasive in parts of Washington, California and Oregon (especially the Willamette Valley). It's also toxic, its toxic component being calcium oxalate. I apologize for the misidentification.

As for eradication, I'm going to copy an answer given on this site 2 years ago by an OSU staff member, Pukhraj Deol, on this topic:

"As a new invasive weed the information for effective control of Italian Arum is still developing. Please see below a link to the detailed information about Italian Arum. Please read the plant identification details and see pictures to confirm the plant ID. Overall there has been limited success with different control methods under trial. No herbicides have been found effective to kill its tubers. One positive result that i found in this report is:

"Vern Holm with the Western Invasives Network has tried many different control methods on Arum italicum and so far the only way he has found to control them is to pour boiling water on roots. He notes that trying to dig them up seems to only spread them around more and damage other plants that may be providing competition"

If you have only a few plants then you can try digging around each plant carefully to completely remove the main and daughter tubers. Please bag and dispose off in garbage. Note: "Please wear gloves as many people have reported having poison oak-like symptoms from touching the sap of this plant."-Jordan Kim, Hood River SWCD
Here is the link to complete report

Here is link to website where public can report invasive weeds. I found two recent reports from Clackamas county and Hood River. Please scroll down to read the responses to both reports."

Here's an excerpt from the 3/16 King County "Noxious Weeds News" article:

"Unfortunately, controlling Italian arum is proving to be as big a challenge as Doug Ewing [former manager of the University of Washington Botany Greenhouse] discovered so many years ago. Digging it out or spraying it with herbicide are both just temporary measures because of the difficulty in eliminating all the tubers. Burning it may be satisfying but is equally short-term. Covering with tarping or sheet mulch may eventually work, but it isn’t known how long the covering needs to be in place (several years of tarping did not control it for one person). As with all invasive plants, prevention is the only sure way to avoid problems. Don’t plant Italian arum in the first place and watch for yard waste dumping on your property where it might get introduced. If it is already present, make sure you don’t move the contaminated soil around. Containment might be the only realistic goal for established populations, although I always hold out hope that with enough persistence any plant can be eradicated."

I have found only one person who felt s/he could control it by removing the red
berries (which are also toxic). Everyone else who's commented on it at the Missouri Botanical Garden website shares your distaste.

Sorry I can't offer you more helpful information,