A confession: I find the word ‘sustainability’ a bit of a hindrance. It’s often under-delivered, and has become a sort of jargon that doesn’t always feel relatable. But by making active choices on the features we create in our gardens, the materials we use and the methods we employ to reduce energy use, we not only create beautiful, functional spaces, we also support ecosystems at a time when they need it the most.
You may also like
- How to design an accessible garden
- Charlotte Harris' 100 must-have plants
- Explore a wildlife friendly meets urban garden
We must seriously consider the carbon impact of construction, demolition-related emissions and issues around the extraction of finite raw materials. It is challenging, but it can create exciting possibilities to think more creatively about what and how we make the bones of our gardens.
Minimally processed materials require less energy to produce compared to materials with high-energy inputs or processes, such as concrete. And while high-quality natural materials, such as stone and hardwood, can be more expensive to buy, they are far more durable and have longer lifespans.
Local sourcing is one way to reduce your impact, by minimising transport emissions, and it grounds your garden in the materials that feel right for the setting. On the Isle of Skye, we’re working on two projects in Sleat where the stone material for the garden is site-won first and foremost; and where we need additional gravel, this is from Kyleakin quarry, just a few miles away, sharing the same geology and appearance.
Materials already on site are always an asset – and that’s as true of waste as of beautiful Scottish boulders. In Berlin, we are making a garden for a creative and social change campus where the existing six-acre site was covered in concrete paving blocks. Over the past four years, inspired by the pioneering work of John Little, we’ve been gradually lifting and crushing those pavers on-site in a phased approach. Instead of sending them to landfill, we’re repurposing them as thick mulches and habitat piles, creating a new, plant-led landscape. By the end of the project, we’ll have planted 25 per cent of this once-industrial site with phytoremediation species and prevented hundreds of tonnes of waste from entering landfill, while fostering a green haven for people and wildlife.
Waste materials are full of opportunity. If you have some left on site – perhaps from a building being demolished – it’s an easy win to use that waste to fill gabion wire baskets, or to crush it into gravel for mulching planting, or, inspired by designer Darryl Moore, painting chunks of concrete in bright colours.
Local Works Studio and Sarah Price collaborated with the community in Erith, London, to develop bricks from local clay for the garden at The Exchange. We may not all have the time to make our own bricks, but sourcing locally and, ideally, pre-loved materials, can yield wonderful results. Local reclamation yards and even platforms such as Facebook Marketplace and Gumtree feature lots of reclaimed treasures.
New ways to build
The way we build our gardens matters just as much as what we put in them. Our soil is a living system teeming with organisms, and it plays a crucial role in plant health, water retention and nutrient cycling. Protecting that as you make any element of the garden is crucial. Avoid people or machinery moving on it in wet weather, and always use boards or track mats.
Innovations in low-carbon construction materials, such as cement-free concrete, can significantly reduce emissions. When we developed a permeable terrazzo paving for our RHS Chelsea Flower Show garden in 2023, the environmental savings of the Cemfree Optima we used were equivalent to 14 return flights from London to Barcelona, for just 60 square metres.
Screw piles or ground screws are a low-impact alternative to concrete foundations, minimising soil disturbance while supporting garden structures like decks, boardwalks and small buildings. And manufacturers and researchers such as Front Sustainable Building Materials and Kenoteq are increasingly developing lower-embodied carbon versions of a traditional clay brick from waste materials.
As with any garden, art and sculpture can be a rich source of inspiration. My wife Catriona and I, for example, have spent the past three years gradually building dead hedges in our garden in Scotland. These hedges of brash, stuffed with cut bracken, act as gentle boundaries, windbreaks and even screening for an unsightly tank, while simultaneously sequestering carbon by returning organic matter to the soil and providing vital wildlife corridors.
One of the newer hedges near a window became home to a wren earlier this spring, and we watched her with joy flit in and out of her nest. This year, inspired by award-winning artist, friend and studio collaborator Laura Ellen Bacon’s incredible woven sculptures, we began weaving finer and more flexible spriggy ends of birch branches into the hedge structure, giving it an undulating, wave-like form.
Natural materials offer endless possibilities. At Gothenburg Botanical Garden, where our studio is designing a sequence of major new botanical spaces, British artist Stuart Ian Frost has transformed a dead tree into an insect haven by drilling various sized holes into it – creating both a stunning sculpture and a refuge for solitary bees and other invertebrates. Remember to use a variety of drill bit sizes and consider a range of horizontal and slightly angled holes, in both sunny and shady spots, to mimic natural habitats and invertebrate preferences. After drilling, remove any of the debris clogging the hole.
Taking it a step further, a stumpery can transform a shady garden into a sculptural space that supports a rich ecosystem. Old stumps, logs, bark pieces and branches come together to form a woodland ‘rockery,’ creating the perfect environment for ferns, fungi, frogs, stag beetles and more to thrive.
Earlier this year, our studio volunteered at the Horniman Museum on the Grasslands Garden perennial cutback. Head of horticulture Errol Reuben Fernandes had us all starry eyed about his sculptural habitat bundles, with the senesced and lignified plants gathered up and tied to sweet chestnut posts to stand, protecting the overwintering invertebrates that may be sheltering or laying eggs in the hollow stems and seedheads.
You may not have posts of sweet chestnut to hand, but a simple teepee structure of a few canes or hazel poles, tied at the top and filled inside with layers of cut-back plants and other organic matter, is an easy way to provide nesting and retreat in the smallest of spaces. These natural obelisks can be repeated throughout a garden to bring structure, connection and function to a space.
Creative ideas for sustainable gardens
Biodiverse roof including with planting into a lean and relatively infertile substrate.
Climate-tolerant trees: top contributors to a thriving ecosystem.
Composters transform food and green waste into garden gold. Hotbins are great for smaller spaces.
Standing deadwood branches set one-third into the soil, providing further habitats.
Recycled crushed brick and other aggregates and paving repurposed from the original garden create permeable paths.
Log stacked domes. Topiary-like, when repeated they provide rhythm and structure as well as habitat.
Reclaimed steel piling retains levels and water, and elsewhere creates raised herb planters.
Varied and undulating soil contours within planting beds create different microhabitats and aspects.
Contoured swale planting absorbs rainwater run-off from the roof.
Reclaimed timber as a deck.
Mixed boundary hedging provides rich wildlife habitats without the carbon impact of fences or walls.
Felled tree trunk for people and wildlife to perch on and enjoy.
Water in the garden, with differing depths. Gentle gradient slopes, planted edges and stones provide routes in and out for wildlife.
Case study for a sustainable garden design
In this garden by Dutch design firm Studio Toop, repurposed concrete pavers have been given a new lease of life as a low wall I’m a great admirer of the work of the Dutch-American garden designer Carrie Preston, founder of Studio Toop. She combines inventive use of materials, meticulous attention to detail and rich, resilient planting. I love her Instagram (@studiotoop), where with great generosity she shares her approach to design, full of ingenious details I wish I’d thought of. We share the same view of the creatively invigorating power of limitations – using what you have to determine what you’re making.
In this private garden, the low walls are made from repurposed concrete terrace pavers. Rather than disposing of these in landfill, Carrie saw the design opportunity in them. These standard 400mm x 600mm pavers have been stacked to form the low walls in the garden at the thoughtful height of 450mm – ideal for seating. So, not only do they define the garden’s structure, but also offer wide perching choices.
A decent foundation and specialist glue fixing between the stacks gives stability. Look closely and you’ll notice that alternating rows are slightly set in, resulting in a stylish and considered shadow gap.
Read more from Charlotte Harris on designing great gardens