In article , Kay Easton
writes
A reply from DeFRA:

"Giant hogweed was imported into the UK at the end of the 19th century
as a large striking garden ornamental. It originated in the Caucasus
mountains of south west Asia and has become naturalised in Britain as a
garden escape. It is a vigorous weed which is found on waste ground,
along railways and in areas of damp soils such as river banks.

Due to the potential harm that its presence can cause other species,
giant hogweed is listed on Schedule 9 and subject to section 14 of the
Wildlife and Countryside Act 1981, which makes it an offence to plant
it, or cause it to grow, in the wild. It would be a matter for the
Courts to determine what constitutes "the wild".

You asked if it would be illegal to grow giant hogweed, under the
existing legislation this would not be an offence, but as you have
indicated whether this is technically feasible without causing it to
spread is another matter.

Giant hogweed is not "notifiable" and there is no requirement for the
public to report this species to Defra."

Well done, Kay. Useful to have a definitive answer.

--
Malcolm Ogilvie