Wildflower enthusiasts are being encouraged to take part in a citizen science survey of cowslips to help monitor the health of threatened meadows.

Nature charity Plantlife is urging the public to continue the legacy of Charles Darwin by taking a close look at the inside of cowslips to judge the genetic diversity of the flowers and the wider health of their meadow habitat.

The yellow spring flower, whose local names include cowslops, fairy cups and bunch of keys, were once as prolific as buttercups, Plantlife said.

But they suffered marked declines between 1930 and 1980, as their ancient meadow and species-rich grassland habitat was converted to intensively managed pasture and silage fields, or ploughed up for crops.

Traditional meadows and grassland now cover just 1% of the UK’s land area, and they are fragmented and neglected, Plantlife warned.

The charity is launching a UK-wide cowslip survey this April, as part of a European study which started in Estonia, looking at the centre of flowers and recording which of two types of cowslip they are.

The “S-morph” or “thrum” has male parts of the flower visible and the “L-morph” or “pin” has only the top of the female part visible.

This difference promotes cross-pollination between unrelated plants, keeping populations healthy and robust, in a phenomenon found in some flowers which was first understood by Darwin, Plantlife said.

In healthy fields of cowslips there should be a 50:50 ratio of the two types, but it can become imbalanced when populations become small and isolated due to loss of habitat, or because of changes to the way the land is managed.

Knowing the ratio of the cowslips in an area will help experts understand more about the quality of those grasslands, Plantlife said.

Reports from researchers in Estonia suggest greater instances of the S morph than the L morph in cowslip populations, which could indicate pressures from land use change and declining habitat.

Declining genetic diversity within populations could also make cowslips more vulnerable to climate change as they will be less able to adapt.

Cowslips, a familiar sight on verges, by footpaths and in meadows, are not themselves currently threatened because they are still widespread, according to Plantlife’s Dr Trevor Dines.

But, as one of the more delicate wildflowers in meadows, which like limited competition from other plants, they are crowded out once fertiliser is added to pastures.

And Dr Dines warned that 75% of remaining wildflower meadows and pastures are less than three acres in size, and “are in tiny fragments – there is no movement between them, they become genetically isolated”.

He said: “A single healthy wildflower meadow can play home to an unparalleled and concentrated diversity – often with over 100 species of wild flowers from cowslips to red clover, and oxeye daisies to spectacular orchids.

“This floral feast in turn supports thousands of species of insects, as well as being vital for carbon capture.

“This exciting new citizen science study will allow us to examine the health of our meadows simply by focusing in on the inside of cowslip flowers,” he said.

If we get enough people taking part, we will be able to take a real health check of the state of meadows

People are being encouraged to count 100 different plants spread across the area they are surveying and record which of the two types of flower they are, which should take around 30 minutes to an hour.

Dr Dines added: “If we get enough people taking part, we will be able to take a real health check of the state of meadows.”

And he said: “If there’s a set of results that come in that’s very skewed, that will be a red flag to look at what’s going on there.”

Dr Dines said Plantlife also wants to know about populations of cowslips in gardens and sown on road verges, to build up a full picture of what is happening across the landscape.

To get started in the cowslip survey, people can visit https://www.plantlife.org.uk/uk/discover-wild-plants-nature/cowslip-survey