The past month has been spent surveying for the critically endangered Spreading Bellflower (Campanula patula) which has been declining steadily in England and Wales since the turn of the 19th century (see previous blog post). We spent around two weeks in total, visiting every known site where the flower has been recorded since 2000, prioritising sites with more recent records. Our aim was to repeat the survey conducted in 2011 by the Science Team here at the Garden to see how the species has fared over the last decade. This challenge seemed insurmountable to begin with, but with careful research and organisation, we planned out each field trip and what sites we needed to visit.
During our first trip we travelled south to Somerset and then to Gloucestershire, where we found two relatively large populations of the Spreading Bellflower. We found nearly 50 individuals in the Mendip Hills, North Somerset, on a steep grassy bank and also on the old ramparts of medieval castle. This is now thought to be the furthest south population of Spreading Bellflower found in the UK, as we didn’t find any individuals in Surrey or Sussex.
Our next stop was a visit to Westonbirt Arboretum, where Spreading Bellflower has been popping up in various locations around the site after the ground has been disturbed. Spreading Bellflower has some interesting habitat requirements, and one of them is that it needs a soil disturbance to bring seeds to the surface in order to germinate. At Westonbirt Spreading Bellflower has been consistently found in the hazel coppice coups, where the traditional method of coppicing has created the required disturbance for the flowers to grow. Coppicing has been used for centuries to manage British woodlands, and involves the cyclical cutting of trees down to the stump and allowing new shoots to grow, providing a supply of small-wood a variety of habitats for wildlife. It is thought that the cessation of traditional woodland management techniques, such as coppicing, has contributed to the decline of Spreading Bellflower in many areas of the UK, so it’s encouraging to know that where coppicing practices continue, Spreading Bellflower can thrive!
On our next field trip, we headed north to Gloucestershire, Herefordshire and Worcestershire reaching as far as Birmingham, before heading back south, following the England-Wales border to Shropshire, Powys and Breconshire. This grand five-day road-trip took us to many interesting sites including woodland rides, an abandoned colliery and even a golf course! We visited 27 sites in total, nine of which were positive for Spreading Bellflower.
Many of the sites where we didn’t find any Spreading Bellflower were overgrown field margins or embankments, and we attributed their absence to a lack of management. However, just because we didn’t find any evidence of Spreading Bellflower in a given location, doesn’t mean it’s not there. One of the difficulties when surveying for this species is that it’s biennial, and so only produces flowers during its second year of growth. Therefore, the plant could have been present as a rosette in its first year of growth, which is nearly impossible to find and identify.
Another challenge in determining whether Spreading Bellflower is extinct in an area, but which may offer hope for conservation of the species, is its long-term persistent seed bank. Therefore, it is possible that the species can reappear at sites after long absences if given the correct amount of disturbance and the conditions are right. This means that there is great potential for collaboration with land owners and organisations to manage the sites where Spreading Bellflower has previously been recorded in order to promote its growth in the future.
There were five sites that we visited where Spreading Bellflower was not found during the 2011 survey, but where we succeeded in finding flowers this year, proving that although the plant can be absent from an area for a number of years, it still has the potential to return!
One of the most interesting and unusual sites that we visited was a cottage garden in Monmouthshire which is home to the largest population of Spreading Bellflower in the UK. This year we found 82 individual plants at this site (compared to just 19 in 2011) making up 35% of all plants found during our survey. This is one of only two remaining Welsh sites where Spreading Bellflower is found, the other site being in Powys where we found just one lonely plant. Therefore, the large population of Spreading Bellflower in the cottage garden is of great importance, and the residents are making efforts to conserve the species and promote its growth. We also returned to the garden to collect seed, making sure not to take too many so as not to impact on its regeneration. These precious seeds will be cleaned and dried, before being safely stored here at the Botanic Garden which is home to the National Seed Bank of Wales. Some seeds will also be sent to the Royal Botanic Gardens, Kew as part of the Millennium Seed Bank to ensure that their collection includes seeds from Welsh populations of UK plant species that are adapted to Welsh habitats. These preserved seeds will act as an insurance policy in case Spreading Bellflower populations in the wild should continue to decline and reach a crisis point, where reintroductions are necessary.
In total, we found 236 individuals throughout England and Wales, mostly confined to the Welsh border area, compared to 295 individuals in the 2011 survey. The next stages of this research project will be to extract DNA from the leaf samples that we collected and conduct genetic analysis to look for levels of genetic diversity and inbreeding in isolated populations. These results will help us to understand how Spreading Bellflower has fared over the past ten years, since the last survey was conducted, and could help inform conservation efforts and management strategies.