Bluebells are Britain’s favourite wildflower and particularly fine carpets attract visitors to well-known sites such as Kew Gardens in London. The appearance of vivid bluebell carpets in British woodlands is a sure and spectacular sign of spring.

The native English bluebell is mostly seen in woodland settings and the larger Spanish bluebell is mostly found in gardens but there is a problem.  Bees will go to both species of bluebell.

Spanish bluebells can hybridise with the native form endangering the survival of the English bluebell.

English bluebells are certainly worth treasuring. It is estimated that Britain is home to half the world’s population of the “English” bluebell (Hyacinthoides non-scripta) and with its unique scent and the very delicate form and structure of the flowers, it is an extremely special flower. But they are now threatened by the introduction of the related Spanish bluebell (Hyacinthoides hispanica), leading to hybridisation and loss of the native, delicate, nodding bluebell. 
There are Spanish bluebells on our allotments and in local gardens.  We can do our bit to help English bluebells by removing their Spanish cousins.  It is best to dig out Spanish bluebells while they are in leaf, as the bulbs are almost impossible to find when the plants are dormant:

• Loosen soil around the bulbs to a good depth and remove all the bulbs and underground runners 
• Where shoots appear from underground runners among clumps of low-growing garden plants, carefully insert a garden fork to its full depth close to the shoot. Work the handle of the fork to loosen the bulb then, grasping the shoot, gently ease the bulb out of the earth 
• Choose moist soil conditions to carry this out and firm in disturbed garden plants

Caution: do not dispose of bulbs by adding them to the garden compost heap and never discard unwanted bulbs in the countryside. Consign them to a black plastic sack and leave for a year before composting.
ref:  RHS website.

Interesting fact:
Bluebells also form carpets without a wooded canopy – for example, on Skomer Island in Pembrokeshire – and point to the locations of ancient forests, long after the trees themselves have vanished. This is because, unlike trees, bluebells have most of their biomass and reproductive organs (the bulb) below ground where they are better protected.

Please do remove Spanish bluebells if you have them on your plot!

How can I tell whether bluebells are native ones or Spanish ones?
The Spanish Bluebell, commonly grown in our gardens, is more vigorous than our native species and can crossbreed with the native to create a fertile hybrid. 

This is a problem, as crossbreeding dilutes the unique characteristics of our native Bluebell.
In a recent study, conducted by Plantlife volunteers across the UK, one in six broadleaved woodlands surveyed were found to contain the hybrid or Spanish Bluebell.
Noticeable differences between the two are as follows: 
Native bluebells…

• have narrow leaves, usually about 1cm or 1.5cm (about half an inch) wide, 
• have deep blue (sometimes white, rarely pink), narrow, tube-like flowers, with the very tips curled right back. 
• have flowers mostly on one side of the stem only, and distinctly drooping, or nodding, at the top
• have a distinct, sweetish scent
• Inside the flowers, the anthers with the pollen are usually cream.

Spanish bluebells… 

• have broad leaves often 3cm (over an inch) wide
• have paler blue (quite often pink and white ones too), conical or bell-shaped flowers that have spread-out tips. 
• have flowers all round the upright stem
• have almost no scent. 
• Inside the flowers, the anthers with the pollen usually blue (although this may vary a little). 

Hybrids between these two are very common, with a whole range of intermediate characters. The hybrids are often abundant in gardens and in woods near to urban areas.
Ref: Plantlife