Invasive native plants such as nettle and bramble are taking over our once flower-rich road verges and putting bees at risk.

Almost 90% of Britain’s wild flowers prefer lower-nutrient soil but they are being crowded out of the countryside as a result of air pollution creating unnaturally rich conditions, particularly on road verges.

Plantlife has identified that road verges are undergoing a dramatic change with plants that enjoy soil rich in nitrogen (much of it deposited from vehicle exhausts) spreading like wildfire including stinging nettle, bramble, rough meadow-grass, cow parsley, Yorkshire fog and creeping buttercup.

The boom of these is crowding out wild flowers that had found a haven on road verges, including some of the UK's rarest and most threatened species such as fen ragwort and wood calamint.

Other victims of the changing verge include wild flowers like tufted vetch, bugle, tormentil, red clover, lady's bedstraw, white campion and greater knapweed.

Air pollution combined with decades of poor management has seen the floral richness of our verges decline by nearly 20%.

So often undervalued, road verges are home to over 700 species of wild flower, nearly 45% of the UK's total flora, – including 29 of 52 species of wild orchid.

As other grassland habitats disappear, verges are a last remaining refuge for many bees, butterflies, birds, bats and bugs.

Red clover and lady's bedstraw, two of the top six verge species that support the highest number of invertebrates - are amongst the plants experiencing the most rapid decline.

Dr Trevor Dines, Plantlife botanical specialist, said: "Vehicle exhausts can result in up to 2.5 kg of nitrogen per mile per year being dumped on our road verges – a rate that only a fraction of our wild flowers can cope with.

"Poor management has combined with pollution to create a perfect storm. Not only have councils adopted an over-eager regime that sees flowers cut down before they can set seed but the mowings left on the verge simply add to the soil richness. Under this management, summer-flowering plants such as eyebright and harebell are disappearing and only the toughest of characters - like nettle and bramble – are prospering."

Plantlife's vision for Britain's road verges is simple: verges remain safe for motorists but are managed for wildlife as a matter of course.

Some simple changes such as cutting less and later in the year and harnessing the power of semi-parasitic yellow rattle to act as nature's own lawnmower can significantly improve the biodiversity on verges, bringing benefits for wildlife and humans.

Plantlife research estimates that if all of the road verges in the UK were managed for nature there would be a spectacular 418.88 billion more flowers, or 6,300 per person in the UK.

Dr Dines said: “If all our verges were managed for nature we would see an area the size of London, Birmingham, Manchester, Cardiff and Edinburgh combined adorned with wildflowers.This surge in pollen and nectar would have a genuinely transformative effect on the prospects of wildlife – half of which we have tragically lost in the past 50 years alone. Re-enlivening our neglected roadside offers us a route away from biodiversity oblivion.”

Plantlife is running a petition calling for councils' management to better benefit flowers and wildlife.