For some time I’ve been very concerned about the damage caused by the pretty, bee friendly but highly invasive plant, buddleia. I was going to ask my City Council if they had policies on this topic but decided to start with the national authorities I thought might be responsible.
Here are links to my questions and answers. The Environment Agency does not deal with these plants unless they are causing a blockage within a watercourse.
“Invasive and injurious plants are not reportable to the Environment
Agency.
Only if weeds are causing a blockage within a watercourse and flooding is
imminent would be reportable to our incident communication service on 0800 807060.”
They then posted useful information on harmful weeds and invasive non-native plants.
https://www.whatdotheyknow.com/request/policies_for_dealing_with_buddle_2#incoming-1221226

The Department for Environment, Food and Rural Affairs (DEFRA) does not have the information at present because “Defra is currently developing a rapid risk assessment for Buddleia which will assess the associated risks and impacts of the species to GB.” So it looks like they are taking this problem seriously, which is good.
https://www.whatdotheyknow.com/request/policies_for_dealing_with_buddle#incoming-1252253 (a couple of the initial acknowledgements were obviously meant for someone else and attached to my request by mistake).

Thanks to the WhatDoTheyKnow site for making it easy to submit public Freedom of Information requests.

Buddleia-DEFRA-FOI2018-18546-Response.pdf (6 downloads)