Knotweed control treatment in a 3-pack kit for the eradication of Japanese knotweed, hogweed and other invasive plants. Powerful herbicides for use by professionals only. Japanese Knotweed is a hardy and invasive bamboo-like plant that can cause costly problems on construction sites and in residential gardens. Effective knotweed control requires high strength herbicidal spray treatments and excavation of the extensive root system. Due to the hardy nature of Japanese knotweed, hogweed and other invasive plants, it can often take several rounds of herbicidal treatment to fully control and erradicate the knotweeds outbreak. Roundup Pro-Biactive herbicide concentrate contains Glyphosate and is sold for qualified professional use only. Users must wear suitable clothing (coveralls), rubber boots and suitable protective gloves (not provided). Dilute at the rate of 1 part herbicide to 40 parts of water for treatment of most prenial weeds and 1 to 40 for treatment of hardy invasive plants like Japanese Knotweed and 1:20 for Ivy Here is a link that might be useful: A PRODUCT

Allelopathy is not the main issue with Japanese knotweed. This is a plant which can grow 6 to 8 feet tall, root down twice that depth and spread to cover acres of allowed. It is the number 1 worst possible invasive species in th UK. I would stop even trying to grow vegetables until the JK has been totally eradicated. If necessary dig up the entire garden! I had it in my woods and it took 3 years to remove by a professional company applying industrial herbicides 3x per year. Unfortunately if it's coming from the neighbour's you are pretty much scuppered unless they control theirs too. This stuff is so awful that it affects property prices over here and there are criminal charges brought against those transporting or dumping it.

Looks like Japanese Knotweed. From the descriptions I have read on the web, it is indeed hard to get rid of once established. Digging up and burning the plant, stems, roots and all is the best course of action. So jump on it right away!

Neither photo is Japanese knotweed. But the first IS a knotweed (aka smartweed, jumpweed) and looks like Persicaria virginiana.