We have alien species of wildlife on our Common, a designation dependent upon their history; it is complicated. An alien species covers several subcategories: introduced, exotic, non-indigenous, non-native species, and a species living outside its range which has arrived there by human activity, either deliberate or accidental. Of course we have native species which are deemed such if they have reached Britain before the land bridge divided us from the continent. Species can also be designated as native when they have flown to Britain, as is the case with many bird species. We also have ‘naturalised’ species: some we accept as they are long established like rabbits and pheasants, some we can be wary of like grey squirrels and Himalayan balsam, some are downright pests like the edible dormouse, and some we would be quite surprised to discover were alien since we are so enamoured of them, like snowdrops.
I have chosen 4 plant species which indicate some problems:
SNOWDROPS: Although formally considered "native", snowdrops are actually introduced and now considered naturalised. Their first known cultivation was in 1597 and first recorded in the wild in 1778. They are native to a large area of Europe, from the Pyrenees to as far away as European Turkey.
BLUEBELLS:.jpg/160px-Hyacinthoides_non-scripta_(Common_Bluebell).jpg)
Don’t get alarmed, they are native but one problem is the purity of the bluebells on our Common. I don’t want to disappoint anyone but I don’t think that they are all true bluebells as many are of a range of colours which means that they have probably been hybridizing with the Spanish hyacinth. I wish that we could recover our population of true bluebells somehow but in the meantime we’d better not worry too much.
So, according to Plantlife (www.plantlife.org.uk), which monitors our flora, there are 3 forms of the bluebell:
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Our native bluebell (Hyacinthoides non-scripta), also known as the wild hyacinth, which prefers woods, but is also found on hedge-banks and sea cliffs. The native bluebell’s deep violet-blue flowers have a strong, sweet scent and the flower stems droop or nod distinctly to one side. They flower the length and breadth of the UK. Britain is home to a significant proportion of the world’s total population and we have an international responsibility to protect this charismatic plant, which has been voted the nation’s favourite wild flower.
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The Spanish bluebell (Hyacinthoides hispanica), native to Portugal and western Spain, was first introduced into British gardens as an ornamental plant around 1680. The Spanish bluebell was first recorded in the wild in 1909.
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The Hybrid bluebell (Hyacinthoides hispanica x non-scripta) - also known as the garden bluebell, this species was first recorded in the wild in 1963. It is mainly found in woodlands, but also grows in hedgerows, churchyards, shady roadsides, rough ground and waste places, and is, of course, common in gardens. It is thought to be most frequent in the lowlands, especially in the entrances to public woodland.
The Spanish Invasion: Spanish bluebell and hybrid bluebells are commonly grown in our gardens. Both are more vigorous than our native species and, once out in the wild, can crossbreed with native bluebells. Crossbreeding dilutes the unique characteristics of our native bluebell. In a study conducted by Plantlife volunteers across the UK, one in six broadleaved woodlands surveyed were found to contain the hybrid or Spanish bluebell.
WILD DAFFODIL: I have discovered that the wild daffodil is native to the Chilterns but now very scarce. I have bought some and have begun to plant them in the damper wooded areas of the Common and I hope that they will thrive and we can enjoy the sight, though in a modest profusion unlike the vast swathes that I have seen in a woodland in Worcestershire.
HIMALAYAN BALSAM (Impatiens glandulifera) is a non-native invasive plant and was introduced as a garden plant in 1839. We have had problems with this (and with a small incursion of the dreaded Japanese knotweed, which we managed to destroy by persistent cutting down). There were 3 main sites on the Common which would have become huge if we hadn’t regularly cut it down before it formed its seeds, as it spreads quickly due to the explosive nature of its seed dispersal, projecting its seeds up to four metres. It produces a lot of pollen over a prolonged season and is attractive to pollinating insects. There is concern that its presence may therefore result in decreased pollination for other native plants.
Graham Thorne