Before joining Barcham Trees as a sales executive in April this year, Bentley Walls spent the previous decade as senior tree officer for the London Borough of Hackney.
In late June, he joined some of his former colleagues on a visit organised by the London Tree Officers Association (LTOA) to the Swedish University of Agricultural Sciences (SLU) at Alnarp, close to Malmö in southern Sweden. The purpose of the visit was to meet Henrik Sjöman and to discuss his work.
Sjöman graduated from the SLU in 2003 as a landscape engineer with an M.Sc in Landscape Planning. After finishing his master's studies, he worked on research and teaching at the SLU with a focus on plant material and vegetation construction. He began work on his PhD 2008, starting with a year in China, studying the Qinling Mountains in search of potential urban trees. During his PhD, Henrik also conducted several field expeditions in Romania, Moldavia, China and North America in search of future species and genotypes for urban environments. In February 2012 He completed his doctoral work with the thesis "Trees for tough urban sites – learning from nature".
He believes it is important to start by trying to understand the ‘personality’ of trees, such as their tolerances and the type of growth they typically make. He feels we should look for ecological matching in our selection of trees, rather than forcing them into situations which they cannot handle. For example, most Scandinavian street trees come from a meadow system, but they would be better using hornbeams and pines, which originate in the steppes system. A tree needs the right weapons and the right strategy if it is to survive.
Bentley-Walls and the LTOA group were shown round Sjoman's Landscape Laboratory test beds and research fields, where he is experimenting with mixed plantings of species not usually growing together. One plot planted had species variation with Himalayan birch, Nordmann/Caucasian fir, and maple with shrub layer of ferns as a combination together, another plot had Pride of India that had been coppiced and hornbeam grown in close planting matrices, and another with sweet birch and walnut and larch. His 'magnolia forest' is also planted with larch, dawn redwoods and oaks, with a view to testing their resilience "The idea may seem strange at first to the purist, but a mixed planting such as this really does work and gives diversity needed", says Rupert. Henrik is keen to seek genetic variations within a species and feels that with some trees there are many forms in nature which are better than those currently in cultivation. For example, considerable variations occur within Magnolia biondii in central China.
Sjoman also has a 'China forest', where he is growing on species brought back from his travels with the intention of assessing whether such trees and shrubs have a commercial future in Sweden. As part of his studies, he visited the Qinling Mountains in a remote part of central China. There are very many species here, but the climate is mild and so many species are not hardy enough for Sweden. On the other hand, trees from northern China are almost too hardy for Sweden, suitable only for Uppsala northwards.
Qinling was chosen because it is the meeting point for the two types of trees and it has not been studied before. It also the home of the giant panda, resulting in a high level of governmental protection and great difficulty in accessing it. While in the Qinling Mountains, Henrik was on the look-out for trees growing on south-facing, dry slopes as those with potential for becoming street trees in Sweden.
Bentley-Walls said Sjoman's research work is sponsored by the Swedish nursery industry, which has a natural and vested interest: "Henrik's research is valued in Sweden; he looks at the whole tree and flora system from start to finish, not just its separate parts, and appreciates the connectivity. I wish we had a similar approach in the UK, which I feel is far behind Sweden in this respect."
The following day the group was taken on a tour of Malmö by Tim Delshammar, a landscape architect, lecturer at the SLU and the city's tree and greenspace manager. A relatively small city, Malmö has just begun forming a tree policy and its tree cover is still young. While London is a much larger city, it has 33 senior tree managers in the 32 London boroughs and the City of London; Malmö has one senior tree manager - Delshammar - in control of the cities tree management.
A visit to Pildammsparken (Willowpond Park) saw renewal of trees and discussions on what could be done given the high use and management practices in pruning; the area is a neighbourhood and park in Malmö, founded for the Baltic Exhibition of 1914. It covers an area of 45 hectares and was formally laid out with a single species of beech of around 4,500 trees that are pruned as high hedges designed around a central open grassed circle.
Bentley Walls was impressed by how the work of Henrik and the SLU is taken into the city of Malmö and put into practice: "At first I felt this was something we should try and emulate in Britain, but on reflection I realised that we do, but we don't join it up as well as they do in Sweden, and certainly don’t have the same equal borough-level support across London in terms of financial and personnel resources provided. It's more like a football league table."