The Barbican

A public realm transformation

Planting Design: Nigel Dunnett  Construction Detailing, Technical Support & Graphics: The Landscape Agency  Client: City of London Corporation & The Barbican Estate Office On-site plant arrangement and setting-out: Nigel Dunnett & Taina Suonio  Plant Supply: Palmstead Nurseries Green Roof Buildup: ZinCo UK

The Barbican is Europe’s largest arts and conference complex, and also includes a significant residential community. It is a noted example of uncompromising modernist architecture, built mostly in the 1970s.   The original design aimed to create a self-contained ‘urban village’, with the residential and public spaces separated completely from vehicle traffic.  Most of the landscape elements, including the water bodies, are ‘podium landscapes’ or ‘landscapes above structure’: roof gardens and green roofs, with car parks, the arts complex, and recreational facilities beneath.

Previously, the roof gardens comprised lawns, flower beds, trees and shrubs, which required continual irrigation and a high maintenance regime.   In 2013, following re-waterproofing of the roof gardens, the opportunity arose for completely new plantings to be installed.  The new design takes a radically different approach.

The planting scheme consists of three main ‘Designed Plant Communities’ that are suited to different microclimates around the site, according to how much sun different areas receive.  Designed plant communities are combinations or mixes of plants that are ecologically compatible with each other, and which operate with many of the characteristics and processes of natural or wild plant ecosystems.

1.  STEPPE plantings in full sun.  These are mixtures of grasses and perennials that are naturally adapted to dry, exposed conditions.  This is the main planting type across the site.  Very colourful, with jewel-like colours, diverse foliage textures and plant forms.

2. SHRUB STEPPE plantings which combine similar mixes of perennials and grasses to the steppe plantings, but with additional low-density shrubs and multi-stemmed trees, to create multi-layered plantings with year-round structure and interest.

3. LIGHT WOODLAND plantings in part-shade, and where the growing medium depths enable tree growth.  Multi-stem trees, widely spaced create a light, open canopy, with a scattered understory of shrubs, and a diverse perennial ground layer.

The Design

This section gives a brief overview of the main design approaches that were applied at The Barbican

Planting Design

The concept for The Barbican plantings is to create continuous and successive waves of colour over long periods of time, through orchestrating a series of dramatic colour washes over the entire site, from spring through to late autumn, and then to finish off the year with a textural array of seeds heads, plant structures and foliage.  Although the plantings are very diverse, at any one time it is only two or three plant species that create the main flowering display.  But these species are repeated over the whole area, creating maximum impact.  I plant in layers so that one set of plants grows up and though the preceding set of plants, leading to that continuous succession.  Naturalistic swathes of perennials and grasses are framed and contained within clumps, groupings and scatterings of multi-stemmed trees and shrubs to give solidity, and a three-dimensional framework throughout the year.

I work very carefully with colour, so that the whole scheme works as a series of controlled colour ‘eruptions’ across the whole area.  An indication of these colour changes through the year can be gained from the seasonal galleries that show the succession of planting month by month.

Instead of planting in large groups, blocks, clumps or drifts, I plant the same species singly, or in small groups, over the entire area.  There is no precise planting plan for most of the species, but the proportion of each species in a mixture is carefully considered and the plants are placed within the planting areas according to a set of rules and instructions.

Because plants that are adapted to extreme dry conditions often have grey or silvery leaves, there is a natural unity to plantings that bring plants together from similar habitats.

Technical, Design and Installation Details

This section contains information on the site, design process, installation, and plant setting out

Before the transformation

Before the transformation project, the plantings in Beech Gardens were contained in raised beds, and consisted of strips of lawn, seasonal bedding plants, over-mature trees and shrubs, and monocultural blocks of grasses and shrubs, all sustained through continuous automatic irrigation.  For more details and images of the gardens before the transformation, click here

Removal of the previous gardens

The previous gardens were removed in 2013 to allow for a full re-waterproofing of the roof deck, before the new roof garden build-up and plantings could be installed.  For more images of the dismantling of the previous gardens, click here

Green Roof Build-Up

The new planting areas were built up from the water-proofed base, using standard intensive and semi-intensive green roof layers.  For more details of the green roof build-up and construction sequence and operations, click here

Design Concepts

For further details of the concepts behind the design of the Barbican transformation project, click here

Setting out the plantings

The setting out method for the plants is crucial to delivering the overall visual effect and functioning of the scheme.  For full details click here

Detailed Information about the Barbican Plantings

1. The Barbican Steppe Plantings

The steppe plantings are the main feature of the transformation project at The Barbican, and these plantings form the basis of the other planting types too.  In nature, steppes or steppe grasslands occur in dry regions with continental climates (hot dry summers, cold winters).  Plants are adapted to these harsh conditions.  The plantings at The Barbican are not attempting to copy any naturally-occurring steppe grasslands, but are a designed version, using perennials and grasses from steppe regions or dry grasslands and meadows.

A matrix of tough, drought-tolerant grasses (Sesleria nitida, Helicotrichon sempervirens, Melica ciliata) creates the backdrop to a long succession of flowering species through spring to late summer.  Later in the summer, and into autumn and winter, the emphasis switches to beautiful textural contrasts as foliage and seed heads take over the display.

The images and text below give a brief overview of the dramatic changes in visual appearance of the steppe plantings over the spring, summer and autumn into winter.  For a more detailed, month by month account of the development of the steppe plantings, and extensive photo galleries, click here

In spring the steppe plantings are full of vibrant colour, as bulbs and smaller perennials flower amongst the grasses and the emerging foliage of the later flowering species.  Species tulips and other small bulbs from arid places are perfect for these sorts of plantings.  Across the whole site, the acid yellow of Euphorbia polychroma and Euphorbia characias mix with the bright colours of the bulbs, and early perennials such as cowslips and pasque flowers

In late spring and early summer the steppe plantings take on the character of sparkling dry meadows, full of pink, blue and mauve flowers

Through June and into early July the steppe plantings undergo a dramatic transformation, as the main summer flowering gets underway.  The grass Melica ciliata begins its flowering, and purple Alliums mix with white Lychnis coronaria ‘Alba’.

Through July the main summer aspect takes hold, with Achillea ‘Terracotta’ and Salvia nemorosa ‘Caradonna’ combining orange and blue  amongst the whites and purples.

In late summer Kniphofia ‘Tawney King’ flowers with the blue spheres of Echinops ‘Veitch’s Blue’ and Verbena bonariensis

In autumn and into winter, the bright flowers of spring and summer are replaced by the complex interactions of foliage colours, plant forms and structures, and textural contrasts.

The images and text above give a brief overview of the dramatic changes in visual appearance of the steppe plantings over the spring, summer and autumn into winter.  For a more detailed, month by month account of the development of the steppe plantings, and extensive photo galleries, click here

2. The 'Shrub Steppe' Plantings

The ‘shrub steppe’ plant community continues the idea of the dry-adapted grasslands or meadow that form the basis of The Barbican plantings, but extends the concept to include a scattered and discontinuous shrub component together with small trees.  As such it is a multi-layered plant community with a strong structure that creates year-round visual interest.  Including shrubs and woody plants gives an extra dimension to the plantings, adds autumn leaf colour and additional flowering, but also importantly increases the wildlife value of the planting through creating additional bird habitat.  The inclusion of the shrubs and small trees was possible where the roof loading capacity enabled a greater depth of growing medium than was possible in the steppe areas alone.

The images and text below give a brief overview of the dramatic changes in visual appearance of the steppe plantings over the spring, summer and autumn into winter.  For a more detailed, month by month account of the development of the steppe plantings, and extensive photo galleries, click here

In April and early May, the dominant visual impression is very similar to that of the main steppe plantings.  The main shrub at this time of year is Amelanchier lamarkii, which in addition to the spring blossom, has young leaves with a distinct coppery tint.

In late spring through to early summer there is a gradual transition from the vibrant jewel-box colours of earlier in the spring to a softer range of purples, blues and mauves.  The bright green bracts of Euphorbia characias fade away, and the foliage of the later-flowering perennials grows taller.  Many of these have blue-grey foliage, and combined with the grey-leaved grasses, the area has a soft greyish green tinge that is perfect for the blue and purple flowers.

The ability to work with slightly greater depth of growing medium in the shrub steppe plantings allowed additional plants to be used that were not suitable for the thinner substrate depths of the pure steppe plantings.  The shrub steppe area is also slightly more sheltered, allowing the inclusion of some taller perennial species.  Below, Lychnis chalcedonica mixes with the first flowers of Kniphofia ‘Tawney King’, Lychnis coronaria ‘Alba’, Achillea ‘Terracotta’ and Verbena bonariensis.

In mid-summer – late June to mid-July the shrubs steppe plantings reach a colour peak as the spring elements fade into the background, and the main flowering combinations of high summer materialise.  The pink flowers of the dark-leaved Elder, Sambucus nigra ‘Gerda’  make a striking combination with the scarlet of Lychnis chalcedonica, the crimson of Knautia macedonica and the blue of Scabiosa columbaria.  In fact the Lychnis is one of the main character species at this time, together with Salvia nemorosa ‘Caradonna’ and Achillea ‘Terracotta’.  Orange with white and a scattering of blue, red and purple characterise this time.

A key flowering shrub is Philadelphus ‘Belle Etoile’ – this low-growing Philadelphus is heavily scented and is planted around public seating areas.

For more details and photo gallery of the shrub steppe plantings in late June to mid-July, click here

In late summer (late July and August) there is yet another colour transition across the plantings as the late summer perennials take over.  The most dramatic plant is Kniphofia ‘Tawney King’ which starts out as strong orange and then fades to pale yellow.  This combines with Achilliea ‘Terracotta’ which by this time has similarly faded to pale yellow.  Strong colour is added through red Crocosmia ‘Emberglow’ and the intense blue of Echinops ‘Veitch’s Blue’.  Verbena bonariensis continues to flower.

In September and October there is yet another transition across the whole site, as a different set of plants come to the fore.  The role and value of the shrubs and small trees becomes especially important.  These were selected in part for their autumn leaf colour display.  Amelanchier lamarkii becomes a beautiful orange, and Cornus kousa a dark crimson red.  The key character perennial is Anemone x hybrida ‘Honorine Jobert’ with clear white flowers.  This perennial establishes in the roof garden where the growing medium depth is slightly greater, but because this is a stressed site, it does not reach the height that it achieves in a more productive site.  The flowering of the Anemone is so profuse that in late summer and autumn white becomes the dominant colour in the shrub steppe plantings.  This is enhanced by this also being the main flowering period of Gaura lindheimeri ‘Whirling Butterflies’ which flowers diffusely amongst the grasses and seed heads of the earlier flowering plants.  Verbena bonariansis continues to flower.

The autumn colour of Amelanchier lamarkii, here with the very graceful and delicate flowers of Miscanthus ‘Undine’.

Below: Cornus kousa

3. The Barbican Rooftop Woodland

The rooftop woodland area at The Barbican is an area of ‘open woodland’ with a multi-layered structure: widely spaced multi-stem trees, a scattered shrub layer, and a rich and diverse herbaceous or ground layer.  It is sited in the darkest part of the area that receives the most shadow.  Many of the plant species used have white flowers to bring as much brightness into this area as possible.

This zone is also the only part of the gardens where trees could be introduced because building regulations meant that the roof could not support trees across the rest of the site.  To bring light into this dark area, the main tree that was used was Betula jacquemontii.  Loading restrictions, and the exposed nature of the site meant that tall trees could not be used, and therefore multi-stemmed birches were used.  The shrub layer was simple: Viburnum x bodnantense ‘Dawn’ was used for its winter colour and scent.  These were widely spaced throughout the area.  A small number of Mahonia x media ‘Winter Sun’ were used to provide an evergreen foil for the birches, and again for their winter scent.  Groups of Euonymus ‘Red Cascade’ were also included for their autumn foliage and bright fruits.

The herbaceous layer was the main focus of the design.  The intention here was to have an evergreen matrix of ferns, wood rushes and other foliage, and within this to have a succession of flowering from spring through to autumn.  Whilst in nature woodland ground flora tends to be at its most floriferous in spring, because this is open woodland with a lot of light able to reach ground level throughout the year, the intention was to maintain flowering interest for as much of the growing season as possible.  In winter, there is a diverse evergreen foliage cover.

The images and text below give a brief overview of the dramatic changes in visual appearance of the steppe plantings over the spring, summer and autumn into winter.  For a more detailed, month by month account of the development of the steppe plantings, and extensive photo galleries, click here

The steppe plantings run into the woodland edges, but gradually take on more of the woodland character.  Here, Euphorbia polychroma merges with the blue flowers of the perennial forget-me-not, Brunner macrophylla ‘Jack Frost’, and the darker blue of Ajuga ‘Caitlin’s Giant’

The dark blue flower spikes of Ajuga ‘Caitlin’s Giant’ with the paler blue of Brunnera macrophylla ‘Jack Frost’ in the woodland area in April

The pink haze of Tiarella ‘Spring Symphony’ with Helleborus foetidus and the blue flowers of Brunnera macropylla ‘Jack Frost’

The white flowers of Aquilegia vulgaris ‘Nivea’ with Geranium sylvaticum ‘Mayflower’ in May

The Snowy Woodrush, Luzula nivea, with white Sweet Rocket, Hesperis matronalis ‘Alba’ with Geranium sylvaticum ‘Mayflower’ and the faded Euphorbia polychroma in May and early June

Aster macrophyllus ‘Twilight’ with Anemone japonica ‘Honorine Jobert’ in August

In October, the ground layer is full of colour with white Anemone ‘Honorine Jobert’ amongst the foliage of grasses and ferns.

The herbaceous ground layer in late autumn and winter

The woodland shrub layer of Viburnum x bodnantense ‘Dawn’ flowering in November 2015.

For more information and photo galleries of the woodland plantings at The Barbican, click here