Eliminate new infestations by de-veging; cut the green leaves when they pop up, preventing the plant from producing foliage. If you do this, the storage organ will eventually run out of steam and the plant will not return. It may take two years or more of de-veging. This invasive, prolific plant is only visible above ground late Winter through Spring.

If it’s already bloomed, hoe off all the flowers and foliage, and hoe again when it comes back. Or, cover the patch with plastic or cardboard which will stay in place for a couple of years. Smothering should be combined with regularly checking for and de-veging escapees that have the strength to grow beneath the plastic until it reaches open ground.

In late Winter go back to the known infestation and start de-veging (hoeing off the foliage) as soon as leaves appear and rinse and repeat until it is gone.

Reportedly, herbicides do not work. Digging may be propagating not eliminating, and since you have to remove and dispose of all of the soil in the garbage, digging is a totally impractical method for large infestations. Read more about this “Undesirable Beauty” at Clackamas SWCD and West Multnomah Soil & Water.