The first update in 20 years to a "red list" of plants found a substantial increase in the number of threatened species. Of the 1,720 examined by the Botanical Society of Britain and Ireland (BSBI), 285 were classed as at greater risk of extinction than the last assessment in 2005. Only 117 were considered less threatened.
The marsh marigold (Caltha palustris), also known as the kingcup for its large golden flowers, is among those at an increased threat. Usually found in wetlands, the flower is now considered vulnerable after its geographical extent shrunk by more than a third in just three generations.
Venus's looking glass (Legousia hybrida), a herb found on chalk arable land and disturbed ground such as chalk pits and disused railway lines, has suffered an even bigger decline in its range. The species is now considered endangered, second only to critically endangered, before it is classed as extinct.
At higher altitudes, the bright-blue flowers of alpine gentian (Gentiana nivalis) are an increasingly rare sight. In 2005 it was found at four sites in the Ben Lawers mountain range in the Scottish Highlands and a fifth at Caenlochan in the Grampian mountains. At Caenlochan, 200 plants had been found in the 1990s, but two surveys last year failed to find any. The species is now counted as endangered.
Overall, 26 per cent of species are now listed as threatened on the vascular plant red list for Great Britain. The last edition of the list, produced in 2005, found 23 per cent were threatened.
There are some reasons for hope amid what botanists said was a bleak picture overall. The fen orchid (Liparis loeselii) has been moved off the threatened list, from "endangered" to "near threatened", after targeted efforts to restore drained and abandoned fens. In 2010 it was growing wild at just three locations in East Anglia and one in Wales. Now it is at seven across England and three in Wales.
Yellow centaury (Cicendia filiformis) and stinking hawk's beard (Crepis foetida) are two other species that have benefited from concentrated conservation projects and are now less threatened.
Nonetheless, the Botanical Society of Britain and Ireland (BSBI) said that the overarching trend was one of decline caused in large part by intensification of agriculture and land lost or fragmented by new homes and roadbuilding. Pollution in waterways was cited as another issue, while climate change is making some parts of the country too warm for certain alpine plants to thrive.
Pete Stroh, scientific officer at the BSBI, described the results as "stark". He said: "Many plants once widespread in our countryside have continued to decline to the point where they are now assessed as threatened."
The report was compiled based on 50 million records collected by thousands of volunteers contributing data to the society between 1930 and 2019. Government agencies such as Natural England will use the findings to inform future action to save the plants.
The updated list came after the government announced that the area between Oxford and Cambridge would be the location for the second of three new national forests promised by Labour, following an initial one slated for Bristol, Wiltshire, Gloucestershire and Somerset. Officials said that the third would be in the Midlands or the north of England, following a competition next year.