FEATURE

Layers of texture in the east moat to create a rich visual experience, © Alister Thorpe

From celebrating the Platinum Jubilee to addressing biodiversity in the shadow of the Tower of London, Superbloom had to meet some astonishing challenges.

It is hard to imagine a more challenging landscape brief than Superbloom: not only the challenge of delivering a spectacular display of annual flowers from early June to September, but to achieve this in the full glare of publicity surrounding the late Queen’s Platinum Jubilee and all within a sunken moat in the heart of London that is overlooked by thousands of passers-by and which just happens to be part of a World Heritage Site and a Scheduled Ancient Monument. Oh, and that’s before you take into account Historic Royal Palaces’ (HRP, the client) desire to deliver a climate and biodiversity responsive project, the unpredictability of climate along this stretch of the Thames, poor existing soils, the lack of access to the site for large vehicles and the significant constraints of archaeology and limited availability of irrigation water supply.

Fortunately, the project managed to meet the majority of these challenges and ended up delivering a wonderful experience during the summer of 2022 for over 250,000 visitors, as well as for countless passers-by and those who caught the spectacle on TV or other media. The following is a summary of some of the technical challenges we had to address and an acknowledgement of some of the aspects that did not go quite to plan.

Soil

The original soil was unsuitable for sustaining Superbloom due to its varied and limited depths, fluctuating conditions and its potential as a weed seed bank. This required the importing and laying of an entirely new soil profile above the existing ground level to provide optimum conditions for germination and the healthy growth of the intended flowering species. Over 10,000m3 of specially engineered top and sub soil was introduced to the moat to a soil specification by Tim O’Hare. The logistics of installing the soil was one of the greatest challenges of the project, not least the physical constraints on access alongside the absolute need to have it all in place by the end of March 2022.

Microclimate

The scheme had to respond to the different microclimates of each side of the moat through the design of topography and species mixes. These differences became more apparent through the period of Superbloom when the cold and dry spring impacted heavily on early germination and coverage of the west and north moat display and when the extremely hot and dry late summer impacted on the intended duration of the flowering display.

Seeding

Over 20 million seeds from 48 species and 16 different seed mix combinations were distributed across the moat to designs by Nigel Dunnett. The intent was to create an impressionist field of flowers that gently transitioned in colour and impact throughout the summer. Trials in the moat and in Sheffield during 2021 provided important information on the seeding, soil and seeding requirements and the watering regime.

Biodiversity

LUC ecologists provided a baseline survey of biodiversity during 2021 and throughout the event in 2022. Unsurprisingly, Superbloom massively increased the diversity and numbers of species using the moat. The significant enhancement of the moat for biodiversity created by Superbloom is attributed to a combination of the following factors:

– Notable increase in flower abundance, species richness and variety of form, favoured by different invertebrates. Whilst most planting was non-native, there was also a significant local native component to the increased species-richness. Native floral species generally provide greater opportunities for native invertebrates than do nonnative flora.

– Increased diversity of substrate form, aspect and compaction increasing niche variety; with more bare ground favoured by invertebrates such as burrowing Hymenoptera (a species group of generally small to medium-sized insects with shared features).

– Introduction of new potential refugia and shade for larvae (taller stand heights, willow structures).

– Notable new faunal colonists has been the Toadflax Brocade Moth Calophasia lunula - a relatively recent colonist to the UK (found on-site as caterpillars).

Drainage + Irrigation

The original site was prone to waterlogging, so additional drainage was introduced into the moat alongside new pathways. The water supply to the moat was very limited and had few hose connection points, so a new irrigation main was laid along the main path route with multiple hose connection points to strategic locations within the moat. During the dry germination and subsequent heatwaves, this system was barely able to cope with the need to water seedlings and the pre-grown turf and required considerable extra labour to manage the hoses.

Services + Infrastructure

Superbloom incorporated LED lighting along the pathways and a soundscape system within the north moat. These each required service routes along the new pathways alongside new ducts for power and water supplies and adjacent to the new drainage routes. A compact services trench was incorporated within the pathway with service chambers positioned as needed.

Special details/artworks

A number of installations were planned within Superbloom to add moments of interest and experience. These included: a large multi-lane slide which acted as an optional entrance into the moat; a distinctive woven willow sculpture (‘The Nest’ by Spencer Jenkins) forming a focal point at the north east corner of the moat; a series of immersive gardens along the East moat including a collection of copper insects by Quist; a soundscape composed by Erland Cooper within the north moat; and a collection of glass artworks by Max Jaquard and Dawn Bendick associated with the Queen’s Garden.

Sketch image of the moat slide into the field of flowers from Tower Hill

© Grant Associates

Rendered plan illustrating the different experiences visitors will have as they journey around the moat

© Grant Associates

This was a lovely experience. Amazing to see the moat filled with beautiful wild flowers. So pleased it will be a permanent garden.

Materials

All materials were chosen to complement and enhance the natural character of the Superbloom flower display. Woven willow edges, barriers and artworks provided a unifying theme across the site along with a consistent path surfacing of Breedon (self-binding) gravel.

Visitors sliding into the moat from Tower Hill

© Alister Thorpe

A new permanent access ramp was required to ensure inclusive access into the moat and this was designed to be consistent with the historic fabric and materials of the Tower using Purbeck stone quarried in Dorset, handmade bricks crafted by the Bulmer Brick and Tile Co in Suffolk and cast iron balustrades fabricated in Hampshire. Willow was harvested from Somerset and Oxfordshire.

Visitors engaging with the flower field

© Alister Thorpe

As a general principle, we wanted the overall atmosphere of Superbloom to be calm and relaxed, and this approach informed the selection of materials from an aesthetic perspective, but as the project was a temporary installation, we felt that delivering a project with strong environmental credentials was paramount. We were after a palette that would complement the stonework: colours, textures and form found around the Tower, yet were low in energy in terms of construction, were low carbon and (where possible) were from a renewable resource. As a principle, the use of concrete was banned across the project; the foundations for the new ramp in the west moat were built from stock bricks held together with lime mortar, a more sustainable and sympathetic traditional solution to modern cement mortar. The use of steel was minimal, limited to providing internal support to some of the willow structures and some secondary structure to secure the slide to the supporting modular framework.

The woven willow nest framing Tower Bridge

© Alister Thorpe

The slide, made of stainless steel in Sheffield, was gifted to the project by The National Trust after it had been used at Cliveden House. Following a safety check by the original fabricators, it was recycled for the project and will be safely stored, ready for reuse again.

Sketch studies of material texture and floral colour

© Grant Associates

Planning, including Historic England (SAM and WHS) Approvals

Planning permission was required for the event alongside approval from Historic England, given the status of the site as a Scheduled Ancient Monument (SAM) and World Heritage Site (WHS) and the client’s intention to retain certain aspects of the project after the Superbloom period. These include the permanent ramp and some of the new pathways and associated infrastructure, plus the intention to retain the new soil profile within the moat subject to final resolution of legacy landforms and levels.

Sketch cross sections exploring topographical arrangements to vary the visitor experience in the moat

© Grant Associates

Operations and visitor management

The interface of Superbloom with the normal visitor management of the Tower of London plus the need to manage peak days of visitor attendance required detailed analysis of visitor flows and management infrastructure which was undertaken by movement specialists Crowd Dynamics. This guided the planning of Tower Hill and all aspects of access and egress from the moat.

Construction of the beautifully crafted new ramp access into the west moat

© Grant Associates

Typically, the Tower of London is not the easiest of environments to negotiate for ambulant disabled visitors, however it was essential that safe and inclusive access was provided to all for Superbloom. The short steep ramp that took people from the Causeway to the moat that had existed for many decades (and was lethal in winter) was replaced with a beautifully crafted compliant one to facilitate inclusive access for all guests. This investment would also serve the moat well into the future, enabling HRP to use the moat more flexibly for a wider visitor demographic. For Superbloom, a long but temporary exit ramp was installed and conceived as part of the experience, rising above the planting and providing views back along the east moat. As part of the legacy proposals, Grant Associates have been commissioned to look at a permanent means of exit out of the moat and on to the Wharf.

Woven willow and shredded rubber flooring in one of the east moat garden spaces with emergent planting appearing in late May

© Grant Associates

Construction

The timescales for delivery of the construction stages were nonnegotiable: if the soil was not laid before the end of March to allow ample time for seeding then the Superbloom simply would not have happened. If the pathways and all the various installations were not complete by the Jubilee Bank Holiday, and the site could not be opened to the public, the project would have failed. Landform, acting as the main contractors, took on these challenges and delivered an exemplary project to the highest quality.

Superbloom entrance with slide entry with completed ramped into moat

© Alister Thorpe

Visitor experience

Being able to walk freely around the moat is a unique experience that has not been possible prior to Superbloom, with the exception of small numbers of guided walks. Combined with the very real sense of immersion within the flowering display and the vibrancy of colours and sense of nature, Superbloom provided a very special memory for all those who ventured into the moat. Here are two comments from visitors:

Floating boardwalk in the east moat

© Grant Associates

It was a really heady experience. I was blown away by the beauty of the masses of flowers, the waves of colour. Walking among them made me feel part of the display, being able to pause and appreciate individual and groups of flowers.

This was a lovely experience. Amazing to see the moat filled with beautiful wild flowers. So pleased it will be a permanent garden.

Rhiannon Goddard, Head of Public Engagement, Projects and Business Management, Historic Royal Palaces said:

Superbloom was a unique and ambitious undertaking for HRP. It was a significant achievement to install a new landscape in the historic moat and to grow from seed a mass display of flowers as we emerged from the pandemic. Despite facing unprecedented weather conditions, the blooms looked beautiful especially during July. We have learned a great deal about the microclimate of the moat which will take us forward into developing the landscape as a future attraction for visitors and home for pollinators and other wildlife.

Climate and Biodiversity Emergencies – lessons learned

For over 100 years, the landscape of the Tower of London moat has principally been one of mown amenity lawn; the definitive nature depleted landscape under human control. Superbloom peeled away that veneer of turf and allowed us to witness a landscape that is much more responsive to the natural environment, much more interesting as a human experience and significantly more valuable for biodiversity.

The west moat in full colour

© Grant Associates

The next challenge at the Tower site is to learn from the lessons of the last year and to shape a new legacy landscape for the moat, optimising these benefits and creating an inspiring example of a biodiverse and climate resilient landscape. These lessons include having a greater awareness of the specific microclimates of the moat through the year and ensuring the future habitats are suited to these unique environments. In addition, to build on the understanding of local biodiversity and to fine tune habitats to better support species in the neighbourhood and not just within the moat itself. Finally, to recognise that the human experience of being within the moat was significantly enhanced by detailed immersion and proximity to the scale and detail of the flowering plants and all the birds and insects that visited the spaces.

Ultimately, Superbloom has been a dramatic illustration of how traditionally-managed urban green spaces can be reimagined as more beautiful and multi-functional landscapes that rise to the challenges of climate change and biodiversity loss whilst still offering joy and delight for human use. We hope it inspires many more projects to be as ambitious and impactful in the future.

Andrew Grant

Author

Andrew Grant is the founder and director of Grant Associates.