IT is, by the discoverer's own admission, "a scruffy-looking weed" - but when it's at the cutting edge of the evolutionary chain, looks just do not matter.

Britain's newest species of plant has been discovered in the unlikeliest spot, on neglected waste ground next to the busy railway station car park in the centre of York.

Excited botanists are cock-a-hoop over the find, which may help shed new light on the development of plants.

Scientist Dr Richard Abbott, of the School of Biology at St Andrew's University in Scotland made the discovery almost by chance while looking for seeds when he stopped off in the city.

Now known as York groundsel, or Senecio Eboracensis, it is one of only five new plant species found in Britain and the US in the past 100 years.

Genetic analysis has shown it is the product of natural hybridisation between the common groundsel, a native British plant, and the Oxford ragwort, which was introduced to Britain from Sicily 300 years ago.

The weed sets seed only three months after germinating and is reproductively isolated from both parents - the essential criterion for a new species.

Dr Abbott is a plant evolutionary biologist who has been researching his subject for the past three decades.

"At a time in Earth's history when animal and plant species are becoming extinct at an alarming rate, the discovery of the origin of a new plant species in Britain calls for a celebration as well as being of great scientific interest," he said.

The plant is believed to have originated in York within the past 30 years.

It is only found in the city and always as a weed on disturbed ground.

Dr Abbott was helped in his research by former post-graduate student Andrew Lowe, now a lecturer in plant biology at the University of Queensland, Australia.

"I made the initial discovery a few years ago and have taken a few more years to research and write up the findings," Dr Abbott said yesterday.

"The plant is a scruffy-looking weed and its discovery is not going to set the world on fire - but it is important from a scientific point of view.

"It is going to help us understand how this process works because we have caught it in action.

"Evolution is happening all around us all the time so new species are being formed, but they normally take a very long time.

"Hybridisation can occur relatively suddenly, but even then examples like this are extremely rare."

He said: "The next few years will be critical as to whether it becomes a fully established component of the British flora or a temporary curiosity."

The research is reported in the latest issue of Watsonia, the journal of the Botanical Society of the British Isles.