Urban tree study investigates tree pit reinforcement products.
The Urban Tree Pit Comparative Study is taking place at Hadlow College, in Kent.
The University of Greenwich has announced that the Hadlow College ‘ground crew’, led by head gardener Alex Rennie, have started work on an urban tree pit comparative study. The project is led by landscape architect and senior lecturer Duncan Goodwin, whose research covers the environmental and social benefits of green infrastructure and urban tree establishment.
‘For trees to become functionally useful within our urban landscapes, they need to establish and reach a state of healthy, productive maturity,’ says Duncan. Unfortunately, he adds, tree planting is often seen as a piece of window dressing to assist a design scheme through the planning process. ‘With little thought about their long-term requirements, it is quite common for trees to be planted within insufficient rootable space. As a consequence, tree roots tend to explore moist and less compacted materials close to the surface and along utility excavations, disrupting paved surfaces and other infrastructure.’
The study is investigating different tree pit systems currently available in the marketplace, Duncan explains, ‘which provide suitable root volumes to enable trees to be successfully planted and established within our hard landscapes’.
During the last two weeks of July, 12 tree pits were excavated by groundworks contractor A Eastwood and, to date, GreenBlue Urban’s Stratacell and Bourne Amenity’s Structural Tree Sand have been installed in six of them. Stratacell is a UK-manufactured, 100% recycled, high-strength, open composite module which clips together to form a structural matrix of cells, able to support the high vertical and lateral loads created by engineered pavement systems. The system is filled with top soil to provide uncompacted rooting conditions beneath the hardscape above.
Bourne Amenity’s Tree Sand was used at the Olympic Park. It was developed in Holland in the 1980s to provide suitable growing conditions for large trees in dense, urban areas, while avoiding problems with compaction from engineered paved surfaces.
This month will see the installation of SilvaCell, from Deeproot, and Cornell University Structural Soil manufactured, under licence, by Landtech. The SilvaCell system comprises a series of open, high-density plastic crates, topped with structural decks, which are able to support engineered pavements and vehicular loads. As with the Stratacell system, the crates are filled with soil to provide the tree with an accessible root environment beneath the hard surface.
Tilia cordata ‘Greenspire’ trees, supplied by Hillier Nurseries, will be planted at the site during National Tree Week in early December.
For more information on the Urban Tree Pit Comparative Study contact Duncan Goodwin.