I'm no gardener, so please excuse my lack of plant/garden knowledge!
We rent a first floor flat with a garden. A completely independent garden with 4 edges against 3 other gardens.
It is a total jungle. We have cut back everything that grows, I don't know what's weeds or plants so I cut back everything. We have 3 huge trees, flower beds line 3 edges with one edge lined in bark and potted plants. We don't spend a lot of time out there to be honest as we aren't green fingered, its hard to maintain as everything in there grows crazy fast.
However, we have Japanese Knotweed. I noticed the other week, one of the few plants I do recognise! And in DP's efforts last summer, he chopped down a lot of it and chucked it on the compost heap (not knowing what it was). Now its, well, uncontrollable. Its killing off all the plants I put in the flowerbed in April. Its grown to astronomical proportions in the last few weeks. Looking at other gardens, its not just ours.
What do we do?? Thing is, we rent privately and the landlords own the property on a leasehold from our local HA - they deal with external stuff and since we're still waiting for them to fix our downstairs porch damaged in the winter storms, I don't see it being sorted any time soon...