How Kew planted an American prairie in the heart of Sussex

The Royal Botanic Gardens at Kew have been in the forefront of planning for our future and an interesting experiment has now been running for several years at Wakehurst, Kew’s country cousin in West Sussex. It starts from the premise that many herbaceous plants, both annual and perennial, will frizzle away if higher temperatures and long periods without water become more frequent. Their roots cannot get down to the depth at which they find the water they need to grow, flower and seed. Such plants are important because they absorb carbon dioxide and contribute to soil improvement. From a study of climate maps of the world to identify the plants that thrive in hotter, drier conditions, the scientists concluded that North America — especially the US — has many plants that have evolved for just such conditions. Some of them are already popular with English gardeners.

In 2019, a team of scientists and gardeners from Kew Wakehurst travelled to North America to collect seeds from wild prairies. Due to the growth of efficient American farming, these prairies are among the world’s most endangered plant communities; only 1% of their diverse ecosystems survive today. The team returned with millions of seeds, some from botanical institutes and some collected in the wild, which they deposited in the Millennium Seed Bank. The following year, a selection was scatter-sown in a new six-acre area now known as the American Prairie.

Some seeds were held back — sown, germinated and pricked out by Wakehurst’s expert propagators — so that 50,000 plugs could be planted in 2021. That year also saw the flowering of the first seeds sown in 2020 — short-lived, pioneering perennials such as Coreopsis and Rudbeckia — although not all the scattered species had fared well. More plugs are prepared every year and the number of different plants is steadily increasing. By 2024, a total of more than 50 different species were established — or, at least, establishing themselves — and 11 new ones flowered for the first time, including wild indigo (Baptisia alba) and American bergamot (Monarda fistulosa). More joined them last year, when prairie plantain (Arnoglossum plantagineum) and fork-toothed ookow (Dichelostemma congestum) were among the species that started to flower.

The wildflower species native to North America differ enormously from one area to the next. Rather than mixing up all the seeds, Wakehurst’s gardeners have been developing a series of different combinations, such as occur in Nature. Their South-Central Prairie, for example, includes purple Allium cernuum and a prairie grass that looks like a fine head of hair called Sporobolus heterolepis — both quite well known already in English gardens — as well as a seldom-seen feverfew Parthenium integrifolium and another grass (Andropogon gerardii) that grows every year to at least 7ft high.

More familiar to English eyes are the prairie plants of the Atlantic Coastal zone, with a mixture of asters that we generally call Michaelmas daisies, plus golden rod (Solidago nemoralis), sunflowers (Helianthus occidentalis) and white-flowered Eupatorium hyssopfolium, best known as an attractor of pollinating insects.

Some species still need a bit of cosseting to get established in the growing conditions at Wakehurst and some will probably fail to do so because they cannot hold their own in the struggle for dominance. The experts are constantly adding new species and creating new mixes. They have also begun to trial end-of-season methods of tidying up — not burning, which is common in the wild, but mowing and raking to discover whether removing dead vegetation will encourage or dampen diversity. Meanwhile, the gardeners are struggling to exclude our native weeds; even our common spotted orchid Dactylorhiza fuchsii seeded itself quite widely among the American plants in the early years of the experiment. As this is a prairie garden, there can be no mulching and no watering. Low maintenance is crucial — ideally, they will create self-sustaining communities. Also, they must be good ornamental plants.

Only a few of the prairie species have been developed and improved by horticulturists. One of the great successes at Wakehurst has been Eryngium yuccifolium, a handsome and vigorous perennial that grows to 5ft or 6ft and flowers reliably from the end of June onwards. The plant has survived our recent summers and thrived because its roots drive deep into the soil in search of moisture. It is, however, a slightly disappointing member of the new prairie because the whole plant is invariably green and white in colour; it would be more desirable if the flowers adopted a shade of blue, as do so many other species of Eryngium.

The best scientific trials have more than one purpose. Many American prairie plants are valuable to pollinators, nectar-feeders and other creatures. Wakehurst is using its new landscapes to investigate the potential of different bees, wasps and hoverflies — the species that visit these non-native plants — as pollinators for plants of economic importance. However, bringing non-native species into the UK always comes with risks and an early study looked at the potential invasiveness of prairie species, by measuring their ‘seed rain’.

Much remains to be put to the test. Is it possible to incorporate short-lived species under English conditions? Will they survive in a mixture that is supposed to be perennial, self-sufficient and balanced? To what extent can one achieve the same balance between species that exists in America itself?

Although conceived as a horticultural study, Wakehurst’s American Prairie is, above all, a scientific exercise. Its plants co-exist in communities that will be the object of long-term study, both environmental and horticultural. It contributes to worldwide research and reminds us of the importance of biodiversity. That is how we will avoid horticultural armageddon or, at least, postpone it.

Find more about Wakehurst and Kew at the Kew website.

This feature originally appeared in the September 2, 2026, print edition of Country Life. Click here for more information on how to subscribe.