Up on the Roof: a visit to the Barbican Beech Gardens

A few weeks ago while in London for the weekend, primarily to watch the World Athletics Championships at the Olympic Stadium, I took the chance to make a pilgrimage to see the Beech Gardens at the Barbican Estate, which have recently been redesigned by Nigel Dunnett.

The Barbican

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For those who are unfamiliar, the Barbican is a large development in the City of London conceived during the aftermath of the second world war, which had left the area devastated, and built between the late 1960s and early 1980s.  The development is notable for being designed in the Brutalist architectural style which is characterised by the dominance of concrete and heavy, rugged forms, and I imagine makes the Barbican both loved and loathed in equal measure (personally, I rather like it). The complex includes both high rise tower blocks and lower rise six storey blocks of flats providing a total of 4,000 homes, and there are also a number of public garden areas incorporated.  The overall design is based around the living areas being raised up above the traffic and therefore the areas of public space are effectively functioning as roof gardens.

Roof Gardens: opportunities and challenges

Clearly, in a densely populated area access to ground level space for gardens is likely to be hard to come by, so one option for incorporating planting is to look to areas at height whether this be walls, balconies or roofs.  A roof garden to all intents and purposes will function in the same way as a more traditional ground level garden with areas of planting, seating and appropriate access points for users (as opposed to a ‘green roof’ which is designed to be looked at rather than lived in).  However, there are some particular challenges to developing a roof garden which will influence plant and material choices and the overall design:

  • Load bearing – unlike at ground level the weight of the features and planting to be used will be a major factor in determining the design of the space.  In some cases roofs may need to be reinforced in order to make them suitable for use as gardens and a structural engineer would need to be consulted.
  • Depth of growing media – related to load bearing is the depth of the growing media (soil, compost etc.) which is available or can be safely included.  Many roof gardens will be based around the use of constructed raised beds and large containers and this will necessarily mean a shallower depth of growing media is available than would normally be the case in a ground level garden.
  • Exposure – planting at height is likely to mean greater exposure to prevailing winds than might be the case at ground level, requiring the creation of some form of windbreak to protect planting and/or the use of plants which are more resilient. There may also be areas of intense sunshine exacerbated by the urban heat island effect, and/or deep or partial shade created by surrounding buildings.  All of this may mean a variety of contrasting microclimates need to be accommodated within a relatively small area.
  • Access – getting plants, materials and any necessary equipment up to a roof area while constructing a garden is likely to be a challenge and may limit what can be built, while ensuring that there is appropriate access for garden users once the garden has been created will also need to be a key factor in the design.

Nigel Dunnett’s Planting Design

The previous planting in the Beech Garden at the Barbican was a more traditional mix of lawns, flower beds, trees and shrubs all of which required reasonably high levels of maintenance and irrigation.  When maintenance work was required to re-waterproof the garden area, Professor Nigel Dunnett of Sheffield University was commissioned to design the planting with a view to creating a lower maintenance, more sustainable scheme.

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Some key features of the the design include:

  • The use of “designed plant communities” whereby complementary plants which are suited to the same environmental conditions and are combined
  • A long flowering season beginning in Spring and continuing through to Autumn whereby a small number of plants flower simultaneously to provide successive “waves of colour” rather than a shorter more intense period of interest
  • Layered planting whereby taller, later season plants grow up through lower growing, earlier season plants
  • Winter interest provided with standing seed heads remaining from earlier flowers, along with the textures and shapes of plant foliage
  • The use of trees and shrubs to provide a permanent framework for the overall planting
  • Repetition of the same plant singly or in small groups across the whole area creating a unified, coherent scheme
  • The use of complementary colours as the planting display changes through the season to provide visual harmony

The main style of planting used in the scheme is termed by Dunnett “Steppe Plantings” whereby a combination of grasses and flowering perennials, which are suited to dry, exposed conditions are used to create a designed version of naturally occurring grasslands.  In some areas this is supplemented by the use of shrubs and multi-stemmed trees to provide structure, while “Light Woodland Planting” is incorporated in areas of partial shade and where the depth of growing media allows.

The Visit

At the time of our visit in August the primary plants in flower were the tall (red hot poker) spikes of Kniphofia ‘Tawny King’, the clustered blue lollipops of Echinops ‘Veitch’s Blue’ and the swaying purple heads, beloved of bees, of Verbena bonariensis, providing a colour scheme of blue/purple contrasting with yellow/orange.  This was occasionally punctuated by the dramatic scarlet of Crocosmia ‘Emberglow’, while in the shadier areas were long stretches of white Japanese Anemone.

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Unlike a traditional mixed border which might be designed to reach a crescendo of colour in mid-summer the overall impression is of a lush mixture of greens, in a wide variety of textures, heights and shapes, providing the canvas for subtle splashes of colour from the plants in flower at the time.  This perhaps makes for a more tranquil space, particularly alongside the small fountain and pools of water which are incorporated into the hard-landscaping. The naturalistic style of planting contrasts markedly with the heavy, concrete architecture of the Barbican development and the wider urban setting of central London, but this works incredibly well.

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Although the garden is a public space it is primarily designed to be used by local residents, and certainly when we visited there were a number of people enjoying the space on a warm, late summer afternoon.  The raised walkways and garden areas are wide and open, and yet the gardens still manage to provide pockets of privacy through the use of tall grasses and the occasional small tree.  I also like the way this carefully designed public realm project is offset by the more humble urban greening of domestic window boxes prevalent along the lines of surrounding balconies.

Lessons for the home gardener

Some take home principles from the Barbican for the domestic gardener:

  • Right plant, right place – the importance of choosing plants which are appropriate for the conditions in which they will be situated is actively demonstrated at the Barbican Beech Gardens.  In this context plants have been selected which are suited to the exposed position of a roof garden, do not require great depth of growing media and which prefer either full sun or partial shade, as appropriate.  The advantages of matching plants to the environmental conditions in which they will grow include more reliable plant performance and less (or no) need for artificial irrigation and feeding.  This is central to developing lower maintenance, more sustainable gardens.

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  • Structure – although the plants have been specifically selected to provide a complementary colour scheme, the structure of the planting is perhaps of greater importance to the quality of the design.  It is recommended that planting schemes should be made up of 60-70% ‘structural plants’ i.e. those which retain a clear, defined shape, in order to provide a framework within which ‘filler’ plants with shorter term interest may be included.  As at the Barbican, trees and shrubs are often used for this purpose but grasses and perennials which have attractive foliage or distinctive seed heads also perform this role.  A neat trick for evaluating the structure of a planting scheme is to take a black and white photo of the area which allows you to see the basic structure of plants without the distraction of colourful flowers attracting your attention.
  • Planning for year round interest – a particular strength of Nigel Dunnett’s design is its longevity of interest through the seasons.  Beginning with Spring bulbs and early flowering perennials, the planting is planned to ensure that there is colour from flowers throughout the summer and into Autumn.  Winter interest is also provided through attractive seed heads and the aforementioned structural planting. This is both important for enhancing the experience of the garden user and for attracting insects and birds through the year with a supply of nectar and seeds.

All of these aspects would be equally applicable in any garden setting but when gardening in limited space are perhaps of particular importance.

Further reading

Nigel Dunnett http://www.nigeldunnett.com/barbican/

Clayton, P. (2017, May). Concrete Chameleon The Garden, p.54-60

All photographs Cooke, A. (August 2017)

 

 

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