"I wish we'd stop growing potatoes, carrots and onions," he writes, "I'm sure we'd all be happier."
As these crops are the reliable favourites of most gardeners who grow their own, he is treading on thin ice. But read further and you discover that Diacono grew those vegetables during his first year as a smallholder at Otter Farm in Devon.
The end result of all his hard work? "Sackfuls of perfectly okay food," he writes, continuing: "I'd dedicated much of spring and summer growing the cheapest, plainest food I eat. Never again."
The experience prompted Diacono to drive his productive garden in a different direction and he set out on a mission to cultivate crops which had either been forgotten or which are rarely found in the UK.
This new book charts his success and shows the rest of us how to make our fruit and vegetable growing a more exciting experience.
"We tend to dedicate most of our growing space to the staples – those maincroppers which are available cheaply and widely, and which taste pretty much the same whether you grow or buy them," he says.
"Branching out challenges the tastebuds and imagination a little, but in return you get delicious harvests, more flavours in the kitchen and you won't be expending all that time and money growing the plainer end of the weekly shop."
Egyptian walking onions and blue honeysuckle may be entirely new to most gardeners, while other plants such as almonds and globe artichokes are well known but not common choices. Diacono says fruit and vegetables that the supermarket won't stock – because they have a short shelf life, are difficult to harvest or are easily damaged are a good place to start.
Take medlars, once a popular British fruit whose quickness to rot saw them used by Shakespeare, Chaucer and many others as a literary metaphor for rapidly fading beauty.
"Medlars have a quite unique rich flavour – somewhere between a date and an apple, and to get the fullest flavour from them you need to let them soften as the frosts hit the fruit," says Diacono. "They start to 'blet' and appear to be going off. This is all part of the lovely process that brings out their flavour."
Diacono leads the garden team at Hugh Fearnley-Whittingstall's River Cottage and is well used to growing plants that will deliver on flavour. Accordingly, his book is full of recipes as well as growing advice.
Mulberries are Diacono's favourite fruit and he says that "one taste is usually enough to convince anyone to grow them." This fruit fell out of favour because some varieties take a decade to produce a harvest, but Diacono says you can now get varieties that will produce berries in as little as three years.
While some of the fruits in the book are available for us to eat ripe off the bush, others require cooking. Is this enough to put people off growing them in our instant-fix society? "I understand why it would put people off – an apple, peach or mulberry straight off the tree is such an instant pleasure, but the less immediate ones are no less rewarding," says Diacono.
"Quince is a fabulous window into those less-instant fruit. Baked or turned into membrillo (quince paste traditionally eaten with cheese) they are a real eye-opener to the unfamiliar." The chapter on growing nuts will tempt many gardeners – who wouldn't want to be able to roast sweet chestnuts from their own tree or harvest a crop of almonds? – but don't these trees grow too big, or aren't they too tender for the average garden?
"Frost-hardiness isn't an issue with most, but size can be," says Diacono. "Fortunately there are new dwarfing varieties which make them more of a proposition for smaller gardens."
Some of the plants could best be described as weird and wonderful. Take fuchsia berries. Many suburban gardens will have a hardy fuchsia growing in them, but how many of us will have tried nibbling the berries? Fuchsia magellanica is the one that's best to eat, and apparently its fruit tastes reminiscent of kiwi, plum and sweet grapes. Adventurous types will have to have a go at growing Szechuan pepper, a spiky bush with leaves resembling those of an ash tree. The berries redden as they ripen and add heat to any dish.
Blue honeysuckle is another plant that sounds tempting – frequently grown and eaten in Siberia, Japan and China, but lesser known here. "It's a great alternative to blueberries," says Diacono, "much hardier and more adaptable, although I'd go for both if you can. They are both delicious, different enough to enjoy independently and blueberries can always be grown in pots."
Diacono says that not all of his experimental plantings have been successful, but that doesn't stop him from trying. His olive trees have been a disappointment, producing some fruit but not enjoying the poor summers and harsh winters we've had of late. Last year he says his kiwi fruit plants were a let-down, while this year they have produced a delicious crop.
If you're a keen gardener, it's likely you've already grown a few of the crops in A Taste of the Unexpected – rhubarb, alpine strawberries, asparagus or nasturtiums, perhaps, but it opens our eyes to how many more possibilities there are. It's clear that Diacono won't stop experimenting with new crops any time soon.
"I've not had a crop from some of the plants I've recently planted – American bladdernuts, Cornelian cherries, mirabelles and plumcots so I'm looking forward to the day (fingers crossed) that they start producing," he says.
If you're in the process of planning your fruit and veg plot for next year, this book will help send you off on a gardening and culinary adventure.
This article was first published in The Scotsman, 18 December, 2010