There seems to be confusion in this thread between "invasive" (aggressive proliferation causing significant displacement or harm to native populations of plants and/or animals) and "aggressive" (rapidly spreading growth in a localized area). Just because you don't see a plant colonizing the area near where you planted a specimen, doesn't in any way mean it's not invasive and causing problems. Also, just because you do, doesn't mean it is invasive. One reasonable way to make a decision about whether, in regards to potential for invasiveness, a plant should be planted in a particular area (state, part of the country, etc) is to review reports from appropriate state agencies or organizations like Exotic Pest Plant Councils. If a plant is reported to be an invasive problem in your area, then planting it is probably not an an environmentally responsible thing to do. If, on the other hand, there is no issue anywhere around your (in your part of the country), then plant away and enjoy.

Getting rid of Japanese knotweed [aka Japanese Bamboo] is do-able; doing so requires persistence. I got rid of a patch somewhat bigger than yours by digging out the plants as best I could and then by assiduously cutting back new growth as soon as it appeared. [This starves the plant for light and interrupts photosynthesis.] After the initial digging out of individual plants, the maintenanceÂclipping new growthÂwas pretty easy. Even mowing works; it just takes near-daily diligence. The patch never recovered and within two years was 100% knotweed-free, and has remained so for the past 15 years. Herbicides work, too, but they will kill the juniper as well and will not completely kill the knotweed's underground root system, so you're still left with clipping. If you do choose the chemical route, spray the knotweed when it is in flower (late summer). But try the non-chemical method; it repays efforts with a lot of personal gratification.

Check with your local community government regarding ordances which require control of noxious plants; also contact your State forestry or wildlife department. I understand that Japanese Knotweed is on the PA list of invasive weeds. Your neighborhood may not have a specific regulation which would apply, but it would probably be worthwhile to contact a Pennsylvania law school or university to learn if there are state laws governing the knotweed invasion. I'm not a PA resident and not familiar with PA laws or regs, however I would consider it unlikely for you to be breaking any sort of regulation by removing the plant's branches and/or roots from your property, but there may be some regulation that would require the neighbor to keep the JK under control. I strongly suggest that you do NOT apply salt to your soil as it can take many years to rinse sufficiently for *any* plant to grow, and [of course] the salt will leach and re-distribute whenever it rains, snows, or is irrigated, which will increase the potential dead area. Here is a link that might be useful: Japanese knotweed

Hi - we managed to get rid of knotweed completely - will tell you how I did it. I'm here because of a BBC article and got me remembering and thinking. I don't understand why everyone says this is so difficult to get rid of it seemed really easy to me anyway. 4 years ago we bought a flat - it had knotweed noted on the survey, it was pretty big area of huge tall weeds, but we haggled the price and bought for cash. Told we wouldn't get a mortgage because of the knotweed. Neighbours told us it was a nightmare they had battled for years and told us all the stories of council officials coming out to look at it and trying to apply for grant funding etc etc to get it dug out with JCB's and burned. Anyway, we decided ourselves to get an estimate from a professional company - priced in the £000's. I did some reading and research about the plant and controlling it. Went to b and q and bought a large quantity of the strongest glyphosate I could find, it said it could treat like 500m/sq. this patch was maybe 20 metres by 5 metres - pretty big for me anyway. It was supposed to be pretty diluted but I only used about 10% water maybe. I also bought a £15 manual spray pump and some gloves and some sponges. I went with some ladders on a Saturday morning in August, it was about 15 degrees C, cloud cover and dry. i coated every single leaf I could with the stuff - several times during the day and again after it dried off or was absorbed. I then found all the thickest stems and bunches and cut them down about halfway, and poured the stuff into the stems - filled right to the top. Then topped them off later that evening - and used the last of the strong spray solution I had made for another final spray coating. Over the next few weeks they starting visibly dying. The winter came and went and by July the following year everything was completely dead. I took plenty of before, during and after photos which I still have. That was 4 years ago I did that and not one single sign of it has returned. It cost me like £80 of materials and maybe 12 hours of my time. I knew nothing whatsoever about Japanese knotweed or plants and gardening and still don't. I was later told that national rail and the local council had actually sent 'a man' every season for 'several years' previous to our buying the place to 'spray the plants' to try and get rid of them. With little success apparently. What I find totally and utterly bizarre is that someone like me, completely clueless about horticulture and plants, was able to completely kill - permanently - a pretty substantial bank of this stuff in like 1 day, with stuff bought from the local hardware shop - and yet the Internet is full of stories and news reports of people spending fortunes and despairing in heartache over it. Was I lucky somehow? Genuinely I've always been curious about this and would welcome input from those more experienced.