Is there any human endeavour as heroic or under-appreciated as plant collecting? When in 1921, at the age of 33, Nikolai Vavilov arrived in Petrograd (now St Petersburg) to take charge of the bureau of applied botany and plant breeding, he found a city racked by hunger. War followed by civil conflict had crippled Russia’s food production and distribution systems – a situation compounded by the seizure of peasants’ grain stores by the Bolsheviks – and Petrograd, once the cradle of the Russian empire, had been transformed into a graveyard. Walking along Nevsky Prospekt, Vavilov was appalled to see starving citizens queueing for mouldy bread. “Westward the sun is dropping,” observed the poet Anna Akhmatova, “and already death is chalking the doors with crosses.”

On entering the bureau, Vavilov was even more dismayed to find the heating pipes had burst and the storage units containing nearly 14,000 varieties of wheat, barley, oat and rye collected by his predecessor had been eaten by famished staff. It was, recorded a member of Vavilov’s team, “a picture of almost complete destruction”.

Yet by 1940, Vavilov had secured new premises in a former tsarist palace in the centre of the city and had amassed the largest collection of seeds in the world. It was a collection brimming with “latent life”, writes Simon Parkin in his riveting account of Vavilov’s plant institute, “a Noah’s Ark of plant matter”. Once cultivated and harvested, the seeds contained sufficient genetic material to feed not only the citizens of Leningrad, as the city had been renamed following Lenin’s death in 1924, but the entire population of the Soviet Union. In the process, Vavilov, a tireless polyglot, would become the most celebrated botanist in the world, feted by scientists from Edinburgh to New York. All the more extraordinary, then, that today he is all but forgotten, a victim of the Soviet state’s desire to erase memories of the siege and the millions who perished in the Nazi onslaught.

Karl Marx wrote that “history repeats itself, first as tragedy, second as farce”. The tragedy is that having amassed a collection with the potential to banish famine, Vavilov was arrested on the eve of war and branded “an enemy of the people”. In this, he appears to have been a victim of a bitter struggle with the peasant-agronomist Trofim Lysenko, who had rejected Mendelian genetics for Lamarckism – the idea that plants and other organisms acquire superior traits from their environments rather than from inherited genetic material. Lysenko believed that through a combination of agronomical knowhow and political will, these traits could be passed down to future generations – a theory that Stalin found appealing.

The result was that when in July 1941, the Soviet authorities began fortifying Leningrad in preparation for the German siege and evacuated precious artworks from the Hermitage, Vavilov’s collection was ignored, though whether this was deliberate or a bureaucratic oversight, Parkin cannot say. What he shows, brilliantly, is how the farce of the seeds’ non-evacuation nearly ended in a second tragedy as Vavilov’s colleagues fought to preserve the collection from raids by starving citizens and their own gnawing hunger. Incredibly, of the 250,000 seeds that Vavilov had amassed at the outbreak of war, the majority survived and by 1967, 100m acres of Russian agricultural land had been planted with material from the institute’s collection. Not only that, but wheat collected by Vavilov in Spain, Japan, Italy and Argentina was crossbred to create high-yielding winter varieties, while potatoes from Bolivia were used to breed hybrids resistant to disease. Today, 90% of the seeds and planted crops in the institute’s collection are found in no other in the world.

Writing in 1737, Carl Linnaeus, the father of modern taxonomy, observed: “When I consider the melancholy fate of so many of botany’s votaries, I am tempted to ask whether men are in their right mind who so desperately risk life and everything else through the love of collecting’ plants.” Imprisoned for the duration of the war, Vavilov would never return to his beloved institute and died of hunger in 1943 at a prison in western Russia. Afterwards, ashamed of their persecution of the world-renowned botanist, the authorities destroyed Vavilov’s case file and did their best to discourage journalists from writing about his achievements. The result was that it was not until the late 1970s that Vavilov’s story and the fate of his employees became more widely known. Even so, Parkin’s is the first book to have been published on the subject outside Russia.

To recreate the story, the author has drawn on the institute’s archives and the diaries and letters of the two-dozen staff to whom it fell to guard the collection during the near-900-day siege, one of the longest of any city in history. In the process, he restores Vavilov and his scientific colleagues to their rightful places in the pantheon of Soviet heroes. But perhaps Parkin’s biggest achievement is to explain how the botanists who sat out the siege resisted the temptation to consume the collection. Instead, he details how they defended the seed bank from looters and braved German bombs to plant potatoes at a field station on the perimeter of the city, thereby ensuring they would produce new tubers that could be stored and preserved for the following year.

In the process, 19 staff died, most of them of starvation while surrounded by containers that could have saved their lives. In this they were guided by the conviction that many of the samples were irreplaceable because of the loss of natural habitats from which they had been collected and that they could contain unrecognised genetic qualities. Their resolve was also a product of their loyalty to Vavilov and their belief in the importance of the scientific endeavour. As one survivor told Parkin: “It was impossible to eat [the collection], for what was involved was the cause of your life, the cause of your comrades’ lives.” Astonishingly, this resolve held despite an explicit order from Moscow to “spare nothing” to save the lives of their fellow citizens.

Although Parkin has done a remarkable job of resurrecting the story of this “forbidden garden”, he admits to frustration that his efforts “could not transport me to the white-hot centre of the story”. It is a frustration this reader shares. Despite a wealth of information about the siege, the thoughts, feelings and cravings of Vavilov’s staff remain tantalisingly out of reach. Instead, Parkin ends on a deflationary note, admitting he has no answer to the question of whether in opting to sacrifice the lives of people in the present for the benefit of future generations, the botanists made the correct moral choice.

• The Forbidden Garden of Leningrad: A True Story of Science and Sacrifice in a City Under Siege by Simon Parkin is published by Sceptre (£25). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply