Saving a species: ‘Living library’ of Britain’s rarest native tree takes root at Killerton

The National Trust is creating a ‘living library’ of trees in east Devon in efforts to help save Britain’s rarest and most threatened native species, the black poplar.

Building on existing efforts up and down the country and with thanks to support from HSBC UK, the conservation charity is forming a living gene bank of black poplar at Killerton, near Exeter, to help save the declining species.

Once as common as oak and beech, drainage of land and demand for faster and straighter growing non-native timber trees has contributed to the gradual decline of the species, leaving the population so fragmented that black poplar has effectively died out in the wild.

Out of an estimated 7,000 [1] black poplar trees left growing wild in Britain, only around 150 of those that have been tested are genetically unique [2]. Many are also male, as historically they were favoured aesthetically over the female trees which produce large amounts of white fluffy seed in spring. Unable to reproduce alone, an urgent effort is needed to form a breeding population of male and female trees to maximise the gene pool and make the species resilient again.

Working in partnership with Forest Research and other community groups to locate and collect a diverse selection of cuttings, rangers at the conservation charity have now planted a total of 80 distinct clones at the Devon site, making it the most diverse population of the species in the country.

Fi Hailstone, National Trust ecologist at Killerton said: “We want to establish a naturally reproducing population of black poplar on the stretch of river we have relinked to the floodplain, the tree’s favoured habitat.

“Black poplars need male and female trees within 200m of each other to pollinate each other. With numbers in huge decline this is not something likely to happen in the wild which is why we are stepping in to create a new breeding population. 

“The trees can live for over 200 years and can grow to 30 metres in height.  Once established, cuttings can be taken from the trees and spread to planting projects elsewhere, acting as a living gene bank, bolstering the resilience of the declining species’ and boosting its chances of survival.”

Over the winter months 27 rooted cuttings of the wetland-loving tree have been planted out, adding to the growing collection already taking root along the 3km of newly restored River Culm floodplain [3].

Initially, Killerton received 43 trees from arborist Jamie Simpson, who works on a similar conservation project in the Borough of Richmond, grown from cuttings from the last wild population of native black poplars situated near the Thames footpath in London.

Further cuttings were collected via the Black Poplar Group [4], which includes the National Trust, Forest Research, The Otter Trust, The Tree Council, Chester Zoo, Suffolk Tree Wardens and groups in Herefordshire and Dorset.

Tom Shuttleworth, Tree and Woodland Advisor for the National Trust adds: “The native black poplar is an iconic tree in the British landscape; arguably our tallest native broadleaf, it features famously in John Constable’s landscape The Hay Wain. Slower growing than hybrids and American poplars, it was a useful timber tree, its wood being strong under flex and temperature and used for cartwheels, brakes, and in mantle pieces.

“It has important biodiversity value to numerous species including the poplar hawk moth, hornets, figure of eight moths and aphids, which in turn support wood ant species.”

At the National Trust’s Plant Conservation Centre in Devon propagation of new native black poplars is already underway and will be expanded using cuttings from the trees at Killerton once they have established.

The propagation of the under-threat trees was kickstarted by donated cuttings from Forest Research who carry out DNA fingerprinting of black poplar, checking to see if they are native, which clone they originate from and if they can be used in the race to create the future generation of the species.

Stuart A’Hara at Forest Research said: “The DNA fingerprinting of black poplars has been very useful in identifying the large-scale clonal (clone) duplication that has taken place with some clones but also highlighting the rarer individuals still in existence.

"The clonal collection at Killerton is a testament to all the good work carried out by the various conservation groups over the years with black poplar at the heart of their work. It will be a tremendous resource going forward.”

Killerton is one of six nature super sites identified by the National Trust for their potential to restore nature across whole landscapes through activities such as planting trees and restoring rivers. For a monthly donation people can ‘Adopt a Plot’ to help to bring nature back, head to nationaltrust/adopt-a-plot to find out more.  

Photo: Fi Hailstone, National Trust ecologist checks black poplar trees planted on the restored floodplain at Killerton, Devon © National Trust Images James Beck.