The many threats to native bluebells

A research study carried out on 22 different species by Edinburgh University and the Woodland Trust found four of the 22 species, including native British bluebell (Hyacinthoides non-scripta) and garlic mustard (Alliaria petiolata), may struggle to keep up with ongoing climate change. All 22 species of plants in the study were found to be sensitive to warming temperatures in spring, by changing when their leaves or flowers emerged. 

Researchers found the plants would foliate or flower an average of three to eight days earlier for each 1°C rise in temperature. The study identified some species which may lack the immediate flexibility to keep pace with changes in their optimum timing (for foliation or flowering), and therefore need a much longer period of multiple generations in order to cope with climate change.

Author of the report Christine Tansey (Woodland Trust and Edinburgh University) said: “Plants have an optimum time for developing leaves and flowers – if they get it right, this will maximise their chances for growth and reproduction. As long-term temperatures change, it may alter the optimum timing for plants to develop.”

Britain is blessed with a large number of spring-flowering wild plants including snowdrop, primrose, wood anemone, lesser celandine and sweet violet, but the native bluebell is almost certainly the most iconic and most well-known among the wider population. However, climate warming is not the only thing native bluebell populations have to contend with. Threats from exotic species and theft are more immediate and acutely serious in effect.

SPANISH BLUEBELL ARMADA
First are ongoing ingression and invasion by and hybridization with the more aggressive Spanish bluebell (Hyacinthoides hispanica), which is overwhelming the native bluebell in many locations. Especially inside urban, suburban and peri-urban woodlands where contamination of native bluebell stands by Spanish bluebells in private gardens nearby is increasing.

Native bluebell is at a disadvantage in two respects. Firstly, the Spanish bluebell plant is more robust and vigorous with ability to outgrow, overwhelm and oust the native species. Secondly, the two species will freely hybridize, gradually replacing the native species with much more vigorous stands of hybrid plants. Given the more southerly and inherently warmer natural range (Iberian Peninsula) of the Spanish bluebell, these apparent advantages over the native British bluebell are likely to be exacerbated as the UK climate warms.

The Forestry Commission recently said: “Growth of the hybrid [native x Spanish] bluebell is vigorous, and overtaking the native variety in many places. This means the British bluebell landscape, however beautiful, is changing. Native bluebells may well be much harder to find for the next generation of woodland visitors.”

One in six broadleaf woodlands surveyed by the charity Plantlife was found to contain a Spanish bluebell or a hybrid between native bluebell and Spanish bluebell. Spanish bluebell, with a native distribution across the Iberian Peninsula, was introduced into the UK over 100 years ago as a garden ornamental. Like other alien invasive plants including Rhododendron ponticum and Japanese knotweed, Spanish bluebell is creating an environmental disaster, although introduction apparently seemed like a good idea at the time.

WIDESPREAD THEFT
Native British bluebells are protected under the Wildlife and Countryside Act which says it is an offence to intentionally uproot any wild plant unless authorised to do so. But this is not doing much for commercially sought-after wild plants, including snowdrops, lent lily (wild daffodil), primrose and cowslip, but most of all native British bluebells, which have been uprooted, stolen and sold illegally for many years.

One such large theft occurred at Fakenham in Norfolk in April this year when 8,000 bluebell bulbs were taken from privately owned woodland. The Norfolk constabulary was called to the woodland after reports of strangers in the area acting suspiciously, discovering several large sacks and mail bags filled with bluebell bulbs that had recently been dug up. The police subsequently said four people had been interviewed in connection with the incident and that the woodland owner was in the process of replanting the uprooted bluebell bulbs. Native bluebell is not the only bulbous spring-flowering species to be targeted on a large scale in this way. In 2019 around 13,000 snowdrops with an estimated value of about £1,500 were stolen from the Walsingham Estate in Norfolk.

AUTHOR’S NOTE
How to distinguish the native British bluebell from the exotic Spanish bluebell:

Native bluebell

• Narrower leaves of 1.0 to 1.5 cm in width at the widest point
• Exhibits a distinct droop like the top of a shepherd’s crook
• Individual flowers are deep blue (sometimes white and rarely pink).
• Bears narrow bell-shaped flowers with tips of the corolla tube rolled right back
• Most flowers are borne on one side of the flower stalk and drooping distinctly or ‘nodding’ at the top of the stalk
• Flowers emit a distinctly sweet scent
• Anthers (borne on filaments) producing the pollen are cream-coloured
• Generally comes into flower slightly after the Spanish bluebell.

Spanish bluebell

• Has much broader leaves which are 3.0 cm at their widest point
• Flower stalks are upright
• Flowers are much paler blue in colour (regularly pink and white) and are conical bell-shaped with tips that spread out
• Individual flowers are borne right around the flower stalk
• Flowers unscented or emitting an unpleasant and pungent, onion-like smell
• Anthers bearing pollen are bluish in colour
• Slightly ahead of the native British bluebell in its period of flowering.

Pure-line Spanish bluebell is commonplace in private gardens. However, hybrids between the Spanish bluebell and the native British bluebell are now very common and actually much more abundant than pure Spanish bluebells in the wider woodland.  Observers are thus confronted with a whole range of biotypes displaying a wide range of intermediate characters. Differentiating between the different biotypes of bluebell in such situations is much more difficult.