Woken a sleeping beast.....

History - New build garden. the first owner was very much a gardener. The second owner was really not. I'm keen to learn and have been working hard to get my knowledge up.

The garden is south facing it is very shaded by a tree and has dry stony poor quality soil.

I've been working on the soil with lots of organic matter, sifting, regular watering and slowly all the original planting is recovering. Current planting is astilbes, hostas, heuchera, hellebores and roses - all doing really well

Today I noticed a stray unrelated leaf poking out of the hellebore mound - Chinese lantern

I had noticed a lone clump last year (under the fence from next door) but the ground was so poor it was strangled and I hadn't realised at that point how invasive they were. After doing my last round of soil conditioning in the last week or so its spread like wildfire along the back fence line and has now moved forwards into my planting! so by improving the beds and planting Ive let the beast in!

On reading up on the treatment it seems the only solution to go full nuclear or it will strangle everything - which will undo two years work to get the garden back up to speed.

And thoughts from the more knowledgable?

Ps - next door dug up their lawn, beds and patios as they were having a full overhaul and landscaping done - however, they ran out of money then split up so the house is now rented to students 'as is'- so its a huge rubble and bin bag filled weed patch. So they are not going to treat any origin plant so it is going to be a defensive action only.