Airing at 7pm on Sunday (February 6), the episode, narrated by David Attenborough, will look at the ways people are helping plants that face extinction.
The seed bank programme in Mid Sussex is home to an underground collection of more than 2.4 billion seeds from around the world.
They are stored at -20c in flood, bomb and radiation-proof vaults so they can be preserved for the future and so that plants can be reintroduced into the wild.
This newspaper was invited on a tour of the seed bank and a full report is coming soon.
In the meantime take a look at our photo gallery of this fascinating project.
People can watch The Green Planet on BBC iPlayer or visit The Millennium Seed Bank website here.
1.
The Millennium Seed Bank at Wakehurst in Ardingly. Picture: Lawrence Smith.
2.
Dr Elinor Breman in one of the drying rooms. Picture: Lawrence Smith.
3.
Seeds in one of the drying rooms at the Millennium Seed Bank at Wakehurst. Picture: Lawrence Smith.
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Drying seeds from all over the world at the Millennium Seed Bank. Picture: Lawrence Smith.