A carpet of bluebells on the woodland floor makes a dazzling sight in springtime - but our most popular native wildflower could be under threat.

The warning comes from the the Worcestershire Wildlife Trust, which says one threat to British bluebells is its popularity in gardens, which leads to wild bulbs being dug up and sold - despite the fact that the bluebell is a protected species and it is illegal to take bulbs from the wild.

Climate change is also a problem. Bluebells flower and grow earlier than most of our wildflowers,but warmer winters could alter this pattern and mean bluebells no longer have the advantage over other species. This could mean bluebells vanishing and could have a knock-on effect on our wildlife - bluebells are an important early food flower for bees, hoverflies and butterflies which feed on nectar.

The Spanish bluebell, widely cultivated in gardens and parks, is another threat to the British bluebell. Hybridisation between the two species can alter its genetic make-up in a way that threatens its long-term survival.

Gill Evans, people and wildlife manager at Worcestershire Wildlife Trust, says gardeners should not plant Spanish or hybrid bluebells in the countryside or near native populations.

There are other ways in which you can help the British bluebell. Ms Evans says: "If you are buying them for your garden, check the bulbs have been cultivated for sale and, if in any doubt, ask the garden centre manager.

"Go and visit the bluebell woods in the Wildlife trusts' reserves for an inspirational sight this spring but stick to footpaths to avoid trampling the plants."

Another way to help is to take part in the online survey Bluebells: Exploring British Wildlife which will be used by scientists at The Natural History Museum to create a map of where bluebells grow in the UK and when they flower. Go to www.nhm.ac.uk/bluebells Ms Evans says: "Worcestershire Wildlife Trust's bluebell woods are stunning just now. There will be plenty of opportunities to visit during Worcestershire Wildlife Week from May 5 to May 13, including Tiddesley Wood open day and Bluebells in Beacon Wood, both tomorrow.

"For details on forthcoming events, visit the trust's website www.worcswildlifetrust.co.uk And remember it is legal to pick but illegal to uproot and sell wild bluebells - and many people believe that it is bad luck to bring bluebells into the house!