Thank you for contacting the Ask Extension for the State of Ohio.

I’m sorry to hear that you are having problems with Italian Arum. This plant is notoriously difficult to control because it spreads both by seed and by numerous small underground tubers/bulblets which you have mentioned. It keeps coming back because any of the bulblets remaining in the soil after you remove the plants, can produce new plants. Disturbing the soil often separates and spreads these bulblets. Birds can also disperse the bright orange-red berries introducing new plants to the area. 

All parts of Italian arum contain calcium oxalate crystals and are toxic. Wear gloves, long sleeves, and avoid contact with sap. Keep children and pets away from plants and berries.

The recommendations I would make to you include:

Continue digging but be more aggressive and in a bigger circle. Dig more widely around each plant and as deeply as practical. Digging is effective only if nearly all tubers and bulblets are removed. Carefully sift the soil to remove all visible tuber and bulblets. Expect to do this several years as any missed bulblets can sprout later. You have mentioned you are already doing this, but you will need to continue to do it every year.

Prevent seed production. Remove and bag all berry stalks before berries are dispersed. Do not compost any of the material. From your response you are also doing this as well.

Minimize soil disturbance as the bulblets can break off and start new plants in this manner.

Continue to Monitor and remove new shoots promptly. Inspect the area several times each year.

Herbicide use: A greenhouse study cited by the Washinton State Noxious Weed Control Board (this is a very prolific problem in the State of Washington) gives some information. The products most readily available to homeowners are usually those containing glyphosate, metsulfuron, 2,4-D, or combinations that include dicamba. However, based on research conducted on Italian arum, these products may kill the leaves but have not been shown to consistently eradicate the underground tubers and bulblets that allow the plant to persist and spread.

Please NOTE: Always read and follow the label instructions before applying any herbicides for proper rate, treatment sites, and timing. Always wear gloves and protective clothing when applying herbicides.

So, in summation, the most successful approach is integrated management: removal of berry stalks before seed dispersal, careful excavation of tubers, disposal in the trash, and repeated monitoring and treatment of regrowth over multiple years.  

It is also important to note that Ohioline does not have any publications on Arum italicum. It is not currently listed on the Ohio Department of Agriculture’s invasive plant list. However, there is an increasing presence of this plant in Southwestern Ohio suggesting that Ohio gardeners are beginning to encounter it more frequently.

Thank you for contacting Ask Extension. The answer to your question was researched and answered using AI information. All references were verified.