I understand that native bluebells can sometimes be albinos and therefore have no pigment in their petals. It is more usual to see white bluebells that are hybrids with the Spanish bluebells. To identify native bluebells of what ever colour I look for the following:
- ratio of length of flower to width (4/5 :1 is native, 1/2:1 is Spanish, in between is hybrid)
- droopiness of flower stem (very droopy with flowers seeming to be on one side of the stem is native, upright with flowers all round ( a bit like hyacinth) is Spanish, in between is hybrid)
- colour of pollen ( white/cream is native, blue is Spanish or hybrid)
- width of leaves (less than 0.75 inch is native, 1" or more is Spanish, in between is hybrid)
- how curled back the petals are at the ends (very curled is native, uncurled is Spanish, in between is hybrid)
I find that I need to use most of these indicators to decide which type a particular flower is. On the Commons we have a lot of native ones, mostly well onto the Commons and filling the glades and under the woodland. Nearer to the road there are some hybridswhich I guess have got out of people's gardens where they have Spanish ones. We hope that no-one puts any Spanish ones on the Commons as they are much more successful at reproduction, germinate more easily, grow into bigger clumps more quickly and come to dominate in areas where they are found. It would be such a shame for our native population to die out from competition.
The photo you sent shows, I think, a hybrid bluebell as the bells have a 3:1 ratio, the petals are not very curled and the habit is somewhat upright. The blue bells around it seem to be more native than Spanish but I suspect they are all hybrids. Where did you see these particular ones?
Some people ( including Richard Mabey) seem to think that we should not resist the spread of the Spanish bluebells. He says that plants have moved from place to place over centuries and this is just another one we will have to get used to. Cross-breeding and competition are facts of nature, increasing diversity and a plant's ability to survive. I think he has forgotten that the Spanish bluebells didn't come to Britain on their own but have been imported by us humans so it is not Nature that is making this competition possible, but humans. I'm a bit surprised that he does not think it worth preserving the variety of species that have evolved so far but I think he takes the view now that Nature knows best so let it do whatever happens without interference from us humans. If we followed this advice we would leave the bracken to cover the whole common, not to say the trees, the ponds would fill up with rushes and New Zealand Pygmy Weed, the heather would die out here and many of the wild flowers would disappear under the blanket of dead bracken and dense shade of the woodland. I suspect Richard Mabey would say " What is wrong with that?" . Maybe it all depends whether you are accepting the natural world as it evolves over time or whether you value the wide diversity that it has at the moment. I suppose it may be that we are only holding up the succession to the wild forest that covered the country millennia ago but it seems to me worth trying to preserve the wide diversity of species where we can.
A few years ago we had a couple of working parties digging up some of the hybrids on the Commons verge but we don't have anyone who is keen to lead that at the moment. If you know of anyone who would like to protect the native ones on the Commons from the invasive pollen which undoubtedly is brought in from surrounding hybrids, let me know and we can have another session, perhaps first identifying where the most Spanish ones are and then digging them out. The best thing people can do to stop the spread, without digging them up, is to take the flowers home and put them in a vase to enjoy, thereby stopping the pollen from getting to the natives and stopping the production of seed which can also be spread to other areas by birds and small mammals. I can't say that we have permission to do this on the Commons as most people will have trouble identifying which are which.