Nurturing rare plants, now seldom found in the wild or glimpsed in gardens, is at the very cutting edge of conservation. Behind the scenes at Kew Gardens, a team of expert horticulturists dedicate their careers to learning how to cultivate these precious plants.
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Below is a list of ten of the most endangered plants in the world, which you’ll also be able to find on display in Kew’s Temperate House, as part of Rare and Extinct (19 October – 17 November 2024), an exhibition in Kew's iconic Temperate House.
The world's most endangered plants
Angels’s trumpets (Brugmansia species)
International Union for Conservation of Nature status Extinct in the Wild
The glorious large trumpet flowers of Brugmansia have ensured that it is a favourite plant in botanic gardens. The seven wild species of Brugmansia were native to South America but are all now only found in gardens.
The absence of wild Brugmansia plants was first recorded in the late 18th Century. It’s likely that their decline was largely a result of the extinction of the unknown animal that dispersed their seeds.
Jess Francis, Botanical Horticulturist at Kew says, ‘Brugmansia are a member of the Solanaceae family, which is the same family as tomatoes and potatoes. The Solanaceae family is quite prone to viruses. To minimize the occurrence of viruses, when taking cuttings, we use a very sharp blade to ensure a clean cut and sanitise the knife between plants so that we don't spread disease.’
Gumwood (Commidendrum robustum)
IUCN status Critically endangered
Gumwood is planted as an ornamental tree on St Helena, and only grows wild in two isolated locations. Fortunately, gumwood seed is stored on St Helena and in Kew’s Millenium Seed Bank at Wakehurst, which means there may be opportunities to reintroduce this plant back into the wild in the future.
Malgorzata Czarnecka, Botanical Horticulturist at Kew says, ‘Propagating cuttings of rare plants gives me the most incredible rush. It’s one of the most rewarding and exciting aspects of my job. We use semi-hardwood cuttings of gumwood, which usually root within eight weeks. We're constantly striking a balance between replicating a species' wild habitat and the realities of a controlled environment. Recently, we've experimented with keeping St Helena gumwood outside in the summer months. They’re coping well with the British summers so far.’
Golden fuchsia (Deppea splendens)
IUCN status Extinct in the wild
The golden fuchsia comes from a small area of the magical Chiapas cloud forest in Mexico. In 1976, American botanist Dennis Breedlove collected several specimens. By the time the golden fuchsia was described in 1987, its only known location had been ploughed over for agriculture. Presumed Extinct in the Wild, all golden fuchsia plants in cultivation are thought to be descended from Breedlove's seeds.
Alex Baribeau, Tropical Nursery Supervisor at Kew Gardens, says: ‘Temperatures in Mexico’s cloud forest vary little from season to season, rarely reaching extremes of heat or cold, so we’re careful to mimic that climate and provide lots of moist compost for the golden fuchsia to grow in.’
Euphorbia obesa
IUCN status Threatened
Over-collecting of Euphorbia obesa nearly led to the extinction of this plant in the wild. Kew’s horticulturists are growing seedlings from seed stored in the vaults at Kew’s Millenium Seed Bank.
Euphorbia obesa is endemic to the Great Karoo in the Eastern Cape of South Africa, which means it doesn’t grow naturally in the wild anywhere else on Earth. The Great Karoo is a semi-desert region stretching 153,000 square miles. The plant looks deceptively like a round stone. It first flowered at Kew in 1889.
Paul Rees, Tropical Nursery Manager at Kew Gardens, says: ‘To produce seeds from Euphorbia obesa you need a male and a female plant. Our only male plant at Kew perished in 2017. Luckily, we collected seeds and stored them at the Millennium Seed Bank just before it died. We’ve since grown seedlings that are about to reach flowering stage and we’re hopeful that there’ll be a male plant among them.’
Pygmy Rwandan waterlily (Nymphaea thermarum)
IUCN status Critically endangered
The rare pygmy Rwandan waterlily is the smallest waterlily in the world. In 2008, it was thought to be Extinct in the Wild. Kew ‘s horticulturists have since successfully propagated new plants, and two previously unknown wild populations were recorded in Rwanda in 2023 and 2024.
Kew Botanical Horticulturist Carlos Magdalena says, ‘Fortunately, botanists from Bonn Botanic Garden, in Germany, collected Nymphaea thermarum plants before they perished in the wild. They sent me seed from the last known plant in cultivation, but none of us here at Kew or in Bonn could work out how to germinate them. Whilst I was busy experimenting, the parent plant was eaten by a rat. Thankfully, my idea to increase the seed's access to C02 by germinating them in extremely shallow water proved successful – they germinated successfully.’
Dwarf ebony (Trochetiopsis ebenus)
IUCN status Critically endangered
The last two known wild St Helena ebony plants were found growing on the side of a cliff-face on the island.
Forest clearances in the 17th century initiated the decline of the St Helena ebony, the beautiful hibiscus-like national flower, and the remaining populations were devastated by grazing goats. After more than a century of presumed extinction, amazingly, two mature Trochetiopsis ebenus plants were found on St Helena in 1980.
Malgorzata Czarnecka, Botanical Horticulturist, says, ‘When our colleague in St Helena, Vanessa Thomas Williams, formerly a Kew employee, showed me where Trochetiopsis ebenus was rediscovered, I was astonished. The two stand-alone specimens were found on a sheer cliff-edged precipice. Their inaccessibility is probably what saved these plants from being eaten by goats like so many of their wild relatives. The horticultural conservationists in St Helena have such a thorough and formidable knowledge of their local flora. I feel very confident about Trochetiopsis ebenus' future on the island.’
Blue amaryllis (Worsleya procera)
IUCN status Critically endangered
Worsleya procera is threatened by commercial collecting and a high frequency of wildfires. Kew horticulturists have successfully propagated this beautiful blue amaryllis and seed from specimens stored at Kew’s Millenium Seed Bank in Wakehurst.
Blue amaryllis grows on the tough granite hillsides of Rio de Janeiro, Brazil. Naturally rare, it is threatened by poaching and wildfires. In 2008, a major inferno wiped out part of the wild amaryllis populations.
Aloe albiflora
IUCN status Critically Endangered (Possibly Extinct in the wild)
Aloe albiflora is grown in many botanic gardens but has not been recorded in the wild since 1955. Kew horticulturists are collaborating with other botanic gardens to ensure the continuation of this snow-white flowered aloe.
Aloe albiflora is a small succulent with spikes of white, bell-shaped flowers, endemic to southern Madagascar. This aloe’s natural grassland environment has been converted to farmland, making it impossible to reintroduce the species to its home. This highlights the importance of conserving individual species as well as their habitats.
Silke Strickrodt, Botanical Horticulturist at Kew, says, ‘With plants as rare as this, collaboration is essential to cultivation. Aloe albiflora cannot self-pollinate. One of our specimens recently developed a flower spike. We’ll make sure that partners worldwide are made aware in case we can cross-pollinate with another flowering Aloe albiflora.’
Falso Maguey Grande (Furcraea macdougallii)
IUCN status Extinct in the wild
The original home of Falso Maguey Grande was the ecologically rich river basin of the Río Hondo in a small region of Oaxaca, Mexico. This species habitat has been degraded by wildfires and Agave plantations that produce the alcoholic drink, Mezcal, but there is hope it will grow here again.
Paul Rees, Tropical Nursery Manager at Kew, says, ‘the Huntington Library, Art Museum, and Botanical Gardens in California shared two bulbils (a bulb like structure) from their single specimen with Kew in 1990. In 2020, one of these flowered, but none of our pollination attempts were successful. We suspect the plants can’t be self-pollinated, which means we’ll need pollen from another, genetically distinct, individual to cross-pollinate it. Most of the Furcraea macdougallii in cultivation came from the same Huntington individual. However, a small community of cultivated plants remains in Mexico. If we can find genetic variability here, there’s hope of reintroducing the species to the Rio Hondo.’
Rhododendron kanehirai
IUCN status Extinct in the wild
Once native to Taiwan, Rhododendron kanehirai is one of the rarest rhododendrons in the world. This small-leaved evergreen shrub prefers a temperate climate, and grows between 1-3 meters tall, producing crimson funnel-shaped flowers in April.
It was once found along the Peishi River, in the mountains of northern Taiwan, but excessive flooding led to its disappearance from habitat and it is now extinct in the wild.
In recent years, only two plants in the world remained, both grown at Logan Botanic Garden. This collection has now been distributed to gardens worldwide, including Royal Botanic Gardens, Kew.
Charles Shi, Botanical Horticulturist at Kew, says, ‘Saving endangered Rhododendron species in mountainous regions of East Asia is critical for preserving these ecosystems. To achieve this, we urgently need horticultural expertise to conserve and distribute these plants, near the brink of extinction.’
This October, 20 plants which are classified by the IUCN as rare or Extinct in the Wild are going on display as part of Rare and Extinct (19 October – 17 November 2024). This temporary exhibition in Kew’s iconic Temperate House will showcase specimens that are usually only found behind the scenes, within our remarkable Tropical Nursery. www.kew.org/kew-gardens/whats-on/rare-and-extinct