The Biggest Beetroot, By Michael Leapman

Musing on a "colossal cucumber" displayed at the National Amateur Gardening Show in Shepton Mallet, The Daily Telegraph suggested: "There should be plenty to go round for sandwiches." Wrong. According to Michael Leapman, who nibbled one as part of his research for this unique horticultural study, such Brobdingnagian gourds are unbearably bitter. Other titanic vegetables are too fibrous to be edible. A Welsh grower informed Leapman of the ignominious fate of his world-champion beetroot (51lb 9oz): "I gave it to the farmer down the road to feed to his cows."

Not only are these monsters unpalatable, they can be profoundly unsightly. The grower of a world-record parsnip (10lb 14oz) likened it to the alien baby in the film Men in Black, while Leapman thought it was "more like an octopus whose tentacles have got out of kilter". Even this mutation has the edge on the world's longest carrot (17ft 3in): "a sickly-looking object... skinny and string-like". Growers of normal-sized competition vegetables look down on those specialising in giantism, but for the rest of us there is something irresistible about super-sized versions of the comestibles that nudge the roast beef at Sunday lunch.

After gasping at a 1,301lb pumpkin in Massachusetts ("It'll taste like shoe leather," said the grower), I purchased a packet of Atlantic Giant pumpkin seeds, but proceeded no further after reading on the label that my putative prize-winners would require 140 days of sunshine and space for 30ft vines. In the UK, the serious grower of big vegetables often has to invest heavily in pricey seeds, nutrients, pumps, heating and, possibly, air conditioning, but the most important element is time. "From the sowing of the first onion seeds in late October to the last of the shows almost a year later, there is no let-up," Leapman reveals. Contrary to popular belief, Leviathan legumes (even leeks) are rarely nobbled and a pleasant camaraderie is the norm.

In a book rich in quiet humour and unostentatious erudition, Leapman visits leading growers from Nottingham to Alaska, which is blessed with both extended daylight and rich volcanic soil. Though the desire to produce unfeasibly vast vegetables is, like all obsessions, not easy to explain, Ian Paton, who smashed the UK record last year with a 1,188lb pumpkin, comes close. "It's not for the money," he told Leapman. "When you're making something grow that can put on 50lb in one day – well, it's just fun."