Deep beneath the rolling Sussex countryside in southern England, a vault sits quietly—cold, secure, and brimming with life’s potential. This is the Millennium Seed Bank at the Royal Botanic Gardens Kew, and in 2025, it celebrates a milestone: 25 years of preserving the world’s plant diversity. Marking this anniversary, the institution has thrown open its metaphorical doors to the world, not just with statistics and stories, but with a high-profile podcast featuring King Charles III, actor Cate Blanchett, and Kew scientist Dr. Elinor Breman. Their conversation, released on October 20, 2025, shines a light on the critical work happening beneath the surface, both literally and figuratively.
For a quarter-century, the Millennium Seed Bank has been a bulwark against extinction, safeguarding more than 2.5 billion wild plant seeds from around 40,000 species. According to the Associated Press, these seeds are meticulously stored in sealed glass jars and foil packets, kept at a frosty minus 20 degrees Celsius (minus 4 Fahrenheit) to preserve their viability for centuries. The vault, built to withstand fire, flooding, and other disasters, is described by researchers as one of the most biodiverse places on Earth—a living archive of the planet’s flora, waiting in the wings should disaster strike.
The journey of a seed to this underground sanctuary is anything but simple. Field collectors venture to far-flung corners of the globe—Madagascar, Thailand, Greece, and even Arctic Sweden—to gather seeds from the wild. As Dr. Elinor Breman, senior research leader in seed conservation at Kew, explained in the anniversary podcast, “Drying is the first step in increasing the longevity of those seeds.” The drying room at Kew maintains a steady 15 degrees Celsius (59 Fahrenheit) and 15% humidity, allowing seeds to lose moisture slowly over about three months. This careful process extends their lifespan by slowing the natural decay that moisture invites.
Once dried, the seeds are cleaned by hand—an intricate, time-consuming process overseen by David Hickmott, Seed Curator at Kew. Technicians use sieves, brushes, and a device called an aspirator, which separates seeds from dust and debris with a gentle puff of air. Only after this meticulous cleaning do the seeds make it to the germination lab, where petri dishes and incubators simulate the light and temperature conditions of their native habitats. “The germination test is our last and most important process,” said Rachael Davies, a germination specialist at Kew. “It gives us an indication that the seeds are alive.” Only those that pass this crucial test are sealed and stored in the vault, where the cold and dryness can double a seed’s lifespan for every 1% reduction in moisture and every 5 degrees Celsius drop in temperature.
Some seeds, especially those from tropical plants with high water content, can’t survive the deep freeze. For these, Kew scientists are pioneering cryopreservation methods, using liquid nitrogen to keep tissues alive at even lower temperatures. The science is cutting-edge, and the stakes are high: nearly half of all flowering plants are believed to be at risk of extinction, according to Kew’s own research.
Since its grand opening in 2000 by then-Prince Charles—now King Charles III—the Millennium Seed Bank has grown into a global partnership, collaborating with 279 organizations in over 100 countries. Its collections have supported projects to reintroduce native species and restore damaged habitats, both in the United Kingdom and abroad. But as Dr. Breman emphasized, “The seed bank is not meant to be the end resting place for those seeds. The next 25 years will focus on using them to restore natural habitats and help combat biodiversity loss and climate change.”
King Charles III, who has remained an active patron of Kew, returned for a special podcast episode to mark the anniversary. Speaking alongside Cate Blanchett and Dr. Breman, the King reflected on the origins of the seed bank and the urgency of its mission. “I think it’s wonderful what the seed bank is doing, but we’ve got to speed up the process. I’m very proud to be a patron of Kew. That’s the great thing. It does wonderful work,” he said during the recording, as reported by Sussex Express.
The anniversary podcast, produced by Fresh Air Production for Royal Botanic Gardens, Kew, is the launch of the fourth season of Kew’s Unearthed series. The episode, titled ‘Unearthed: The need for seeds,’ is followed by a new three-part series delving into the past, present, and future of the Millennium Seed Bank. Listeners are taken on a journey with Cate Blanchett as she follows Kew scientists and their global partners, from field collection to seed banking, and even to the edge of space, where seeds are being sent for research.
Blanchett, who serves as Kew’s ambassador for Wakehurst, described the experience as “an absolute joy” and “revelatory.” She added, “I witnessed the invaluable science that is undertaken around the clock by the dedicated team at Wakehurst and their partners across the world. The real and ever-growing threats to our precious planet must be addressed and the work of the Millennium Seed Bank is a linchpin for our collective ‘Thrival.’ Seeds may be tiny, but they are of monumental importance to us all.”
The Millennium Seed Bank’s origins trace back to Millennium Funds, established to combat the effects of biodiversity loss and climate change, ensuring the world’s plants are safeguarded for future generations. In the years since, Kew has trained more than 3,000 scientists from 70 countries in seed collection and storage, building conservation capacity far beyond the UK’s borders. To further expand its work, Kew recently launched the £30 million ($40 million) Seeds Future Fund, aiming to support new research and partnerships worldwide.
The need for such efforts is growing ever more urgent. Dale Sanders, biologist and former director of the John Innes Centre in Norwich, told the Associated Press, “Within species there is incredible genetic diversity, which protects against disease, climate change and other threats. Maintaining that diversity is essential if we want to preserve the diversity of life itself.” With the world’s population expected to swell by 2 billion by 2050 and new agricultural land running out, the genetic resources housed at Kew and its partner institutions could prove indispensable.
From orchids smaller than a grain of sand to palm seeds the size of a fist, each jar in the Millennium Seed Bank represents a species that could one day help restore ecosystems on a changing planet. As the bank looks ahead to its next 25 years, the focus is firmly on action—moving from preservation to restoration, and from safeguarding to rebuilding the world’s fragile biodiversity. The seeds may be silent and still, but the message from Kew and its partners is anything but: the future of life on Earth may depend on what lies beneath Sussex’s green hills.
