Some of the UK’s rarest plants are at risk of extinction unless action is taken to look after the road verges that have become their final refuge, it has been warned.

Species such as fen ragwort and wood calamint are now only found on road verges, with fen ragwort hanging on in just one native spot near a burger van on the A142 in Cambridgeshire, conservation charity Plantlife said.

The charity has unveiled its top 10 list of threatened plants growing on road verges. They are:

A rare Fen Ragwort plant - of which there was thought to be just one in the wild 30 years ago - is tended at a nursery at Flaf Fen, near Peterborough, Cambridgeshire.
Fen Ragwort (Andrew Parsons/PA)

1. Fen ragwort (Senecio paludosus) – critically endangered. Always rare, it once grew in scattered locations in fenland in East Anglia, but its final native site is a roadside drainage ditch beside the A142 near Ely, Cambridgeshire, where a single plant grows.

Despite protection for the site, the plant is often buried in plastic cups from a nearby burger van. In an effort to save it, seeds have been grown and reintroduced to several former fenland sites, and it has survived for 20 years at one.

2. Spiked rampion (Phyteuma spicatum) – endangered. A plant of coppiced woodland in Sussex, it is now restricted to just eight sites, including along several wooded lanes in mid-Sussex where it grows in the verge and along hedgerows. The verges have no special protection.

Undated handout photo issued by Plantlife of crested cow-wheat. Some of the UK's rarest plants are at risk of extinction unless action is taken to look after the road verges that have become their final refuge, it has been warned.
Crested cow-wheat (Plantlife/PA)

3. Crested cow-wheat (Melampyrum cristatum) – endangered. A semi-parasitic plant of woodland rides, edges and hedgebanks in eastern England, whose largest populations are now on road verges, such as the 2,735 flowering spikes counted along a 70-metre stretch of road verge nature reserve in Cambridgeshire.

4. Tower mustard (Turritis glabra) – endangered. A type of cabbage which likes places where the soil has been disturbed. Nearly half of its remaining 30 sites are on road verges, including the M50 near Bromsberrow in Gloucestershire, the Thetford Bypass in Suffolk, and a road verge near Kingsley in Hampshire.

5. Velvet Lady’s-mantle (Alchemilla monticola) – endangered. Six very rare and closely related species grow in upland haw meadows and pasture in northern England and loss of these habitats means they are increasingly restricted to verges.

6. Yarrow broomrape (Orobanche purpurea) – vulnerable. A parasitic plant which grows on the roots of yarrow which is only known in around 40 grassy sites in Britain, and more than a quarter (28%) are roadside verges.

Undated handout photo issued by Plantlife of sulphur clover. Some of the UK's rarest plants are at risk of extinction unless action is taken to look after the road verges that have become their final refuge, it has been warned.
Sulphur Clover(Andrew Gagg/Plantlife/PA)

7. Sulphur clover (Trifolium ochroleucon) – vulnerable. A creamy yellow clover found in grassy pastures in eastern England, but intensive agriculture means two-thirds of sites (68%) are now verges, some of which are threatened by a lack of mowing or road widening.

8. Wood calamint (Clinopodium menthifolium) – vulnerable. It grows in a single valley on the Isle of Wight, where the only plants are found along a narrow road bordering a wood, but conservation has increased the population from five clumps in the late 1950s to nearly 2,000 flowering shoots in 2012.

9. Welsh groundsel (Senecio cambrensis) – near threatened. This “groundsel on steroids” with bigger, brighter flowers, is only found in Wales, including on roads, and is especially abundant along the A5 and B5070 between Chirk and Llangollen.

10. Wood bitter-vetch (Vicia orobus) – near threatened. Sensitive to both overgrazing and undergrazing, this vetch cannot survive in modern intensive silage fields but is now a plant of grassy road verges where abundant populations are found, though they are at risk of being mown.