Network Rail has been ordered to pay £15,000 compensation for damage caused to homes by the invasive weed spreading from its land.
Property experts warned the outcome of the case had the potential to alter the legal landscape for owners of public land and are calling on them to be aware of the issue.
Neighbours in South Wales sued Network Rail after claiming knotweed growing on a railway embankment had spread to the foundations of their nearby homes.
They said the value of their properties has been hit by the knotweed's roots.
It is now reviewing the judgement but the Property Care Association - which represents professionals in the invasive weed control industry – has said the ruling is likely to have implications across the UK.
Steve Hodgson, chief executive of the PCA, said: "This landmark ruling is one that could change the landscape for those responsible for tracts of public land.
"Japanese knotweed is a destructive plant that can have a hugely damaging effect on the urban environment and any knotweed or other invasive species growing on their land could potentially spread to neighbouring properties.
"Homeowners living adjacent to public land could now be emboldened to take action too, so this puts the onus on squarely on landowners to control and remediate any issues, particularly near houses, as soon as they come to light."
Hodgson added: "The species can be identified and treated with minimal impact, but its effective eradication is a job for the experts and I’d urge anyone who thinks they might have an issue to seek professional advice."
The PCA set up the Invasive Weed Control group in 2012 to act as a source of competent and trained contractors and consultants.
Claimant Robin Waistell told courts he was unable to sell because the rail body had ignored requests to tackle the invasive weed on the bank behind his home in Maesteg, south Wales.
It is understood the rail infrastructure body was refused immediate leave to appeal against the ruling.
Network Rail faces potential legal costs running into six figures after losing the case in Cardiff bought by Waistell and a neighbour.
He wanted £60,000 compensation for loss of value and was awarded £15,000, with a third of that to pay for an insurance-backed guarantee on a herbicide programme to tackle the knotweed.
A spokesperson for Network Rail said: "We are aware of the outcome in this case and we are currently reviewing the judgement in detail."
In 2015 UK ministers accepted a national eradication programme would be "prohibitively expensive" at £1.5bn.