Invasive Alien Species in Northern Ireland

Hyacinthoides hispanica, Spanish Bluebell

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Hyacinthoides hispanica
© Fiona Maitland
Hyacinthoides hispanica
© Fiona Maitland
Hyacinthoides hispanica
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Hyacinthoides hispanica (Miller) Rothm., (Miller) Chouard, (Mill.) Chouard, Mill.
Spanish bluebell and its hybrid with the native Irish bluebell, Hyacinthoides non-scripta (L.) Chouard ex Rothm. are both widely grown in gardens. The hybrid is in fact probably far commoner than the true species.
The Spanish bluebell is similar to the native bluebell, but has the flowers arranged all round the stem, not hanging to one side, and has broader leaves, and shorter, 'fatter' flowers. The hybrid Spanish bluebell has combinations of characteristics intermediate between the Spanish and native Irish species. Flower colour in hybrid populations in gardens can vary between blue, lilac, pink and white, but are normally blue in wild populations.
Country of origin
Spanish bluebell is a native of the Iberian countries and North Africa. The common Irish bluebell is native to Ireland, Great Britain and western Europe as far south as central Spain. The hybrid appears to have originated within the British Isles where both species meet in gardens or other plantings.
Location in Ireland
The Spanish and hybrid Spanish bluebells are recorded mainly from County Down and south County Antrim, but with scattered reports from elsewhere. It is probable that most reports of Spanish bluebell are misidentifications, the hybrid being apparently far commoner. The woodlands in Stormont Estate, Belfast, which have both species and the hybrid, are publicly and easily accessible.
Life cycle
Both Spanish bluebell and its hybrid with common bluebell are bulbous species, producing the fresh season's leaves in about December. Flower spikes appear in May and the flowers are insect-pollinated. The hybrid is fully fertile and produces abundant seed. All bluebells retain much of their seed in the papery fruits until well into the winter. Leaves die back completely from about the end of summer.
Wildlife and habitat impacts
There is no known adverse impact on animal wildlife. The principal concern is the contamination of native bluebell populations by the genes of Spanish or hybrid bluebells, and the possibility of 'hybridization out of existence' (introgression) of the native plant. This threat may be overestimated.
Key vectors
Spanish bluebell and its hybrids are mostly found in gardens, demesnes or parkland, where they were deliberately introduced. Their escape into wild situations is probably linked to the careless disposal of garden rubbish containing bulbs. The degree to which natural woodland is contaminated with Spanish and hybrid bluebells is unknown, but is probably not extensive. Seed dispersal is largely by wind over short distances, and the invasion of uncontaminated populations of native bluebells by windblown seed is unlikely to be very great except where they are situated close to gardens or parks containing the non-native plants.
What you can do as an individual
If you purchase bulbs labelled 'Spanish bluebells', you will almost certainly be
buying the hybrid, not the pure species.
If you wish to purchase native bluebell bulbs for a garden, ensure they are from local Irish sources and have been raised in cultivation, not stolen from the wild. Make sure that they are not the Spanish bluebell or its hybrid (the horticultural trade is notoriously inaccurate with naming and labelling plants).
Do not knowingly plant Spanish or hybrid bluebells in or close to any woodland or ground containing native bluebells, and never throw away rubbish containing garden bluebell bulbs, either into your rubbish bins (they could grow on rubbish tips) or 'over the garden fence' or onto outdoor tips or dumps. If you need to get rid of unwanted garden bulbs, kill the bulbs first by drying them off over a period of weeks. Remember that compost heaps may not destroy the bulbs.
Management measures
The complete removal of Spanish or hybrid bluebells from an extensively contaminated site is probably uneconomic and undesirable. The focus of management should be on prevention of further spread into natural woodland or other natural habitats by the removal of garden escapes as and when discovered. More research on the extent of the problem in Northern Ireland is required, as there are suggestions it may have been exaggerated in Great Britain.
Management groups
Plantlife International has carried out a survey of the Spanish bluebell in the UK see their web site.
Further information
Text written by:
Paul Hackney, Keeper of Botany, Ulster Museum