I sent this e-mail to the environmental agency and received the answer, both below. I am now even more confused,
Are my concerns unfounded?
This may be of little or no importance, but I thought there was some sort of problem with Japanese knotweed, and looked it up on the internet.
I volunteer at a hospice one day a week, my job is to arrange flowers for areas of the hospice. We receive a lot of floral tributes from various florists, which we dismantle and rearrange. A lot of the tributes contain Japanese Knotweed , and this has make me question if, by putting it in the household waste, is in fact doing harm to the environment? If this is the case, then maybe we as a country should not be encouraging the use of this plant as a general foliage, used in the Florist industry.
Regards Carol West
Thank you for your email regarding the use of Japanese Knotweed in floral arrangements.
Japanese Knotweed is not reportable to the Environment Agency and we have no regulatory powers regarding the management of this weed. The Environmental Protection Act 1990 lists the plant as a 'controlled waste' and it must be disposed of properly. The Environment Agency regulates these activities. It is an offence to plant or cause Japanese knotweed to spread in the wild under the Wildlife and Countryside Act 1981.
The plant is mainly spread through the fly tipping of green waste containing Japanese knotweed and by vehicles transporting contaminated soil and waste between sites. However, if the plant is being spread by the incorrect methods of removal (i.e using a strimmer and spreading the plant) this is reportable to your local police Wildlife Liaison Officer. You can find contact details of your local police station on the UK Police Service website.
Our website has guidance and clear pictures of Japanese Knotweed, if this plant is being used in the floral arrangements as you suspect please contact your local Wildlife Liaison Officer.