How Kew’s carbon garden is tackling climate change via planting

A climate change bed uses herbaceous perennials arranged in stripes moving from cool blues to hot reds to show how we are heating up at an alarming rate. It starts with the lower temperatures of cool blues such as aconitum, salvia and nepeta and graduates up to the hot oranges and reds of plants such as crocosmia, geum and helenium. The bed is based on the climate stripes created in 2018 by Professor Ed Hawkins at the University of Reading. The coloured stripes show the rise in global temperature over the past two centuries, exponentially increasing in recent decades.

Plants help to lock away excess CO2 in the soil, the seabed and woody tree trunks. Some 99 per cent of carbon on Earth is sequestered underground. The garden illustrates this process with a coal seam in a rock face showing how carbon is stored in sedimentary rocks and fossil fuels, created over millions of years from dead plants and animals.

“Carbon is a vital element; it’s in all living things and we wouldn’t be here without it. Without CO2 in the atmosphere we’d probably freeze because it has a warming effect. It’s the balance that we’re upsetting,” Wilford says.

We are destroying these habitats and disrupting the carbon cycle through activities such as mining and deforestation, which are releasing these stores back into the atmosphere.

The long-term, common sense solution is to save our planet by being less destructive. In the meantime, we can select plants tough enough to handle extremes of weather. The garden’s choice of plantings is based on Kew’s ongoing scientific research into carbon capture and the role of plants in combating climate change.

The garden, started in 2021, is divided into zones. The dry zone is designed for extended periods of drought with minimal watering. It shows what our own gardens might look like in 30 or so years’ time and includes lavender, echinacea, agastache, euphorbia, panicum, yucca, olive trees and Italian cypress.

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“It’s not just Mediterranean planting, however. You have to choose plants that can cope with drought but also survive our winters. There are lots of plants in cultivation now that can cope with those varying conditions,” Wilford says.

The plants are aided by good drainage, which Kew has boosted by creating a mulch of sand and crushed concrete that was removed from the site before work commenced.

“If we do get lots of rain the plants won’t start rotting because the free draining [bed] will help them cope with excessive rainfall. The roots will go down into the soil while the neck of the plant will be protected,” Wilford says.

The mulch will also lock in moisture to alleviate periods of drought.

Drainage is bolstered by a rain garden and bioswale (trench) built to capture and slow down excess run-off and floodwater, using its bowl design and vegetation to percolate the rainwater slowly down into the soil. There are wildflower meadows, grasslands and hedgerows to boost biodiversity, which in turn produces healthier plants. Robust specimens need less cosseting and are able to process more CO2.

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“Grasslands are significant in terms of the amount of carbon they absorb and are an important sink. Some prairie grasses have huge roots that go [up to five] metres down into the soil. Natural, undisturbed grasslands contain a lot of carbon in the soil,” says Wilford.

Trees are crucial for storing carbon in their trunks as well as providing shade and filtering out pollutants from the air. Kew has chosen species it thinks will withstand our changing weather, underplanted with shade-loving shrubs, grasses and perennials. These trees include acers, oriental hornbeam, cercis, oriental beech, and parrotia (Persian ironwood).

“They’re not the standard trees you might expect to see in a garden or on the street. If we’re going to use trees to hold on to carbon there’s no point in planting any that in 50 years’ time are going to be struggling and then die,” says Joe Richomme, garden supervisor.

The project’s aim is not to preach but to encourage us to look more closely at our own garden, adds Wilford. To think about our design and to observe how our plants are doing over time and whether we need to replace them, and if so, with what. No one knows for sure what the future holds — the only certainty about climate change is that it will bring us increasingly uncertain weather patterns. Kew’s new venture is not set in stone but will evolve as the climate continues to change. Its creators will observe and adapt just the same as gardeners should be doing at home. Like any garden, it is bound to throw up surprises, says Wilford.

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“It’s going to be a case of watching. It’ll be an interesting experiment to see what does well and what doesn’t, even in the climate stripes.”

Carbon Garden ideas

Rain garden: a bowl-shaped shallow depression and rill planted with vegetation that captures excess rainwater and releases it slowly down into the soil. Mini rain gardens underneath down pipes prevent drains from becoming overloaded

Mixed landscape: varied planting is visually stimulating and boosts biodiversity with stronger plants to absorb more CO2. Zones could include dry, shady, woody, wildflower or ornamental grasslands. Consider porous materials for hard landscaping such as gravel, permeable paving or woodchip.

Hard landscaping: improve soil drainage by adding organic matter such as well-rotted compost. A mulch of composted bark or a gravel substrate will filter heavy rainfall and lock in moisture in dry periods.

Suggested species and cultivars

Dry zone: Agave parryi; Cistus creticus; Lavandula ‘Hidcote’; Panicum virgatum ‘Prairie Sky’; Salvia yangii; Verbena ‘Bampton’

Shady zone: Blechnum spicant; Cyclamen repandum; Dryopteris filix-mas; Galium odoratum; Hosta ‘Devon Green’; Tiarella cordifolia

Shady ground cover and shrubs: Daphne laureola; Epimedium pinnatum; Hydrangea arborescens; Phuopsis stylosa

Rain garden planting: Carex divulsa; Geum rivale; Iris ‘Gerald Darby’; Osmunda regalis

Trees: Cornus mas; Gleditsia triacanthos ‘Skyline’; Koelreuteria paniculata; Ostrya carpinifolia; Zelkova serrata

Flower meadow: Daucus carota; Erica carnea; Geranium pratense; Penstemon digitalis; Sesleria ‘Summer Skies’

Wildflower meadow: Achillea millefolium; Leucanthemum vulgare; Primula veris; Silene dioica; Trifolium pratense;

Grasslands: Anthoxanthum odoratum; Bromopsis erecta; Festuca rubra; Lolium perenne

kew.org: carbon garden opening July 24, 2025