By Alex Kirby
BBC News Online environment correspondent
Botanists in the UK are starting a search for some of the country's best-loved and most threatened plants.
Cornflowers, an evocative British sight (Image: Jane Smart/Plantlife)
They want to find the best sites in Britain for wild flowers that thrive in arable crops.
The botanists are enlisting the help of farmers and agronomists in tracking down the floral hotspots.
They hope landowners will help to save the plants by farming in an environmentally sensitive way.
The project is being launched by Plantlife International and a group of partners which includes English Nature, the Crop Protection Association and the Botanical Society of the British Isles.
Plantlife says: "The 25 wild plants that farmers and agronomists are being asked to look out for are all considered to be 'indicator' species.
EMBLEMS OF A LOST ENGLAND
Modern industrial farming techniques have now pushed many arable "weeds" close to extinction.
"The occurrence of one or more of these plants should indicate the presence of a rich and diverse wild plant community comprising many other important species, such as cornflower, corn buttercup and rough poppy."
Arable wild flowers have been increasingly squeezed out of meadows themselves to survive on the margins, in unploughed headlands or other barrier strips.
Researchers say they are the group of plant species whose numbers have declined most rapidly in recent years.
Rough poppy (Image: Nick Stewart/Plantlife)
This is often because of farming policies "that encourage increased crop yield at the expense of countryside stewardship", Plantlife says.
Threats to the plants' survival include crop-spraying and hedgerow removal.
Martin Harper, Plantlife's conservation director, said: "It's vital that we do all we can to secure the future for this charismatic and threatened group of plants - but first we have to find out exactly where they are.
"That's why we're hoping as many farmers as possible will help us to find out if they have any wild plant treasures hiding in the fields."
Night-flowering catchfly (Image: Andrew Gagg/Plantlife)
He told BBC News Online: "Botanists haven't always been very keen on going into arable fields, often because of access problems, so we don't have a great knowledge base to start out from.
"What's happened to arable wild flowers - the UK's most threatened plant group - is in one sense the old story about increasingly intensive agriculture.
"But we do now accept that they're part of our cultural heritage, and part of our biodiversity.
"We'll be searching only with the permission of the landowners, and we hope to be able to target advice on wild flower management and conservation, and to encourage more people to join agri-environment schemes."
A field guide to rare arable plants, containing information on over 100 species, was recently launched by English Nature.