IT may not look like much, but this little green shoot is one of Oxfordshire's most precious treasures.

Greater water parsnip, once common across the UK, has all but vanished over the past 200 years and now struggles on at just a few dozen sites.

In Oxfordshire, it grows at just two places in Marston and Headington, and last year the Marston population had its worst year since monitoring started, when all three mature plants – which should have flowered – were eaten to the ground by deer.

Despite being two metres tall when fully grown, this waterside giant is at risk of disappearing in the county.

Now the green icon of tenacity has been given a lifeline by volunteers who have increased its growing sites in Oxfordshire by 50 per cent in one day.

Last Thursday, Oxford ecologist Judy Webb – best known to many as chairman of the Friends of Lye Valley in Headington – led an expedition to plant a set of greater water parsnip seedlings at Pinkhill Meadow by Farmoor Reservoir.

The project has been co-ordinated by the Freshwater Habitats Trust, a national conservation charity which happens to be based in north Oxford.

Trust regional officer Pete Case said: "Freshwater Habitats Trust has carefully created ideal conditions on Pinkhill Meadow Flagship Pond site.

"Greater water-parsnip is very particular, requiring just the right amount of disturbance from grazing animals.

"Too little and other plants overpower it; too much disturbance and the flowers are grazed and trampled, unable to set seed.

"The hope is that Pinkhill Meadow, sandwiched between Farmoor Reservoir and the River Thames, will be the perfect new home."

Pinkhill Meadow is one of 70 top-quality pond sites – called Flagship Pond sites – that Freshwater Habitats Trust is working to preserve in England and Wales.

Each site is carefully surveyed and cared for to protect the pond plants and animals that make it special.

At Pinkhill Meadow, surveys have shown it to be one the richest pond sites in the country.

Work to clear some of the more vigorous vegetation at Pinkhill, making space for smaller, fragile species, has already been funded by the Trust for Oxfordshire’s Environment (TOE2).

The Greater Water-parsnip seedlings planted out were grown by Oxford Botanic Garden, using seed collected from one of the other Oxfordshire sites.

Mr Case added: "Creating seed banks and introducing plants to new sites is vital when plants are unable to spread themselves because the countryside is no longer suitable for them."