It is a tough one. Pulling is not effective because the roots tend to run sideways then down. Which herbicide and when was it applied? Burning could work but only if done repeatedly at the first signs of new growth.

Nope...one year I burned weekly throughout the summer..all that happened was that it got thicker.....smaller leaf but that didn’t last long...by autumn it was larger and taller than ever...also new growth usually reverts from the pink/white/green version I bought to a taller, all green version....

Somewhere out there is a site that says "You could try painting the glyphosate on the Houttuynia with a small foam paint brush. " I have done this successfully with a pesky weed called a bindweed. Just paint some leaves with the undiluted stuff. Wait and paint the survivors. It's a pain in the a..ah back but it works.

Not only have I done the paintbrush thing many years - I’ve also snipped the leaves at the base and injected concentrated round-up into the stem/root with a syringe.....both painting and injection work on the plant above ground...but in 2-3 weeks the houttuynia is back three-fold or more....I’ve had many invasive plants including running bamboo that grew 20’ tall...they have been easy to treat compared to houttuynia..and much less invasive...houttuynia will creep and root, it will spring up from underground roots 4’ away..and it also flowers and spreads seed...it should never been permitted into garden centers.....I bought a single pot about 18 years ago...it’s now in every one of my 30 beds (I hybridize daylilies for fun- well, not fun any more)....first year it looked like it barely survived...second year-so-so—-3rd year it sprang up in all directions 5’ around the mother plant....it only takes a 1/2” piece of root to begin a new plant so you try not to break it when digging it...but you will...and it only makes it proliferate more...when I asked a county extension agent what to do I was given only one solution that works....move!