Two developments have changed that. The first was the introduction of compost-stuffed growing bags which you can place almost anywhere, in a back yard or even on a sunny balcony, and get decent produce with hardly any effort except regular watering. The second has become evident in the past few years to anyone who cruises the aisles of the supermarket: the proliferation of bonsai vegetables, perfectly formed and outrageously priced, based on the questionable notion that small is succulent.
Now seed merchants have begun to packet ranges of mini-vegetables or "patio" produce, selected as being suitable to grow in containers. And at the Royal Horticultural Society's huge Hampton Court Flower Show (the last day is today) Gardening Which? magazine has devoted much of its stand to a demonstration of how to cram vegetables into confined beds and tubs, making maximum use of every square centimetre of soil or compost.
The centrepiece of the magazine's stand is the "desktop vegetable plot", in which an extraordinary variety of vegetables are being raised in a bed measuring 8ft by 3ft, the size of an average desk. The bed has even been given the accoutrements of a desk, with Tumbler tomatoes - the variety developed for growing in han-ging baskets - spilling out of drawers at its edge.
"A lot of our readers grow mainly flowers and shrubs but they still like the idea of growing vegetables, even though they don't want a huge family- sized plot," says Brian Grout, the magazine's research manager. "We're saying that they don't need to give a large space to vegetables but they can still grow enough to enjoy. The philosophy is that you cram in the stuff and keep it small, and as soon as you pull something out you replace it with something else."
In other words, if you want to grow mini- vegetables, you only need mini-space to do it. If, for instance, you plant cauliflowers 3in apart rather than 2ft, they will form heads the size of golf balls instead of footballs, and will draw gasps of admiration from dinner guests as part of a minimalist vegetable platter.
Even if they start to run to seed - as they are just as likely to do in this miniaturised form as when grown to full size - you can use the individual stalks like broccoli, cook the small outer leaves like cabbage, and steam the thicker ribs like asparagus. The point is to make maximum use of everything that comes up.
"Sometimes you're harvesting stuff when it's not quite ripe," says Dr Grout. "That does not matter. Courgettes only need to be about as big as your little finger to be edible. If you want a great heap of vegetables on your plate, there's no point in growing them small, but if you're stir-frying, all of a sudden it's different."
One benefit of picking them small is that they don't have to get very far down the line to be a success, Dr Grout adds. By this he means that you may harvest your courgettes, for instance, before the pervasive mosaic virus has a chance to fell them, as it does with sickening regularity on my allotment. The disadvantage is that some vegetables, if they are not allowed to reach maturity, have not developed much flavour.
The Hampton Court display is the fruit of two years of experiments by Joe Maiden, who runs the Gardening Which? trial beds at Golden Acre Park in Leeds. Mr Maiden, who gives gardening advice on local radio and satellite TV, has a reputation for the unorthodox.
"He'll try anything," Dr Grout affirms. "Even if it isn't in the rulebook, he'll give it a try." One of his latest experiments has been to maximise the yield from a single tomato plant. Among the methods he tried was to pinch out the growing point and let up to four side-shoots grow on - the reverse of the time-honoured technique. By pinning the main stem to and training each shoot vertically up an individual support, rather like training a peach tree against a wall, the yield was increased by 50 per cent and more.
Mr Maiden says: "A lot of the things we do here are way out. They're my own ideas based on 35 years of gardening. But the secret, like with most things, is to have good growing conditions." The desktop-sized raised beds contain 18in of soil mixed with mushroom compost.
His Hampton Court display is essentially a work in progress, with vegetables in different stages of maturity. A vital part of the strategy is to keep a supply of reserve vegetable seedlings in small polystyrene cups or yoghurt pots. Then, as soon as you pull out a few marble-sized radishes, you can replace them with an incipient lettuce, keeping the space fully used.
Among the other crops that Mr Maiden has been growing on the patch are onions, leeks, broad beans, beetroot, curly kale, red cabbage, red chard and red brussels sprouts. (The prevalence of red demonstrates that he is conforming to the current fashion for growing vegetables that are decorative as well as edible.) Mr Maiden even has some sweet corn - suitable for these conditions because it grows tall and makes the best use of the space.
Three seed companies - Dobies, Suttons and Mr Fothergills - market ranges of between 10 and a dozen mini-vegetable seeds. Dobies' catalogue includes a list of recommended spacing between plants: mostly from half an inch (leeks and carrots) to 6in (kale), but more for marrows and courgettes. Leeks grown in such confined conditions will never grow large enough for stews, but can be pulled in summer and eaten raw in salads like spring onions.
This year Unwins introduced 10 "patio vegetables" chosen for growing in containers, mainly of compact form. According to David Jeffery, the firm's vegetable seed manager, the response has been better than expected. The table on this page lists the varieties in order of popularity, based on the number of packets sold. Cucumbers were the surprising favourite, possibly because, like sweet corn, they make efficient use of the space.
But you need not restrict yourself to specially marketed varieties when deciding what to grow in pots. Almost anything that can be grown in the ground will do well in a properly watered and fertilised growing medium: a standard growing bag or multi-purpose compost is fine if you have no environmental objection to using peat; a loam-based or coconut fibre compost is the thing to use if you do.
On a recent visit to the RHS demonstration garden at Wisley, Surrey, I saw many vegetables thriving in containers, including climbing French beans, garlic, shallots, coriander, parsley, seakale, rhubarb and potatoes. Some gardeners like to plant one or two potatoes in a bucket in the autumn, to get new potatoes for Christmas lunch.
Traditionalists will regard all these trends as nothing more than fads. Allotment holders who pride themselves on producing large quantities of basic vegetables for their families will not easily be converted to the cause of growing finger-sized parsnips in a window box, or of mixing red lettuce with the busy lizzies on the flower border. I assume that it will be a long time before the local flower show introduces classes for the smallest leek as well as the largest, but maybe a class for the best container of vegetables is not far off.
8 The Hampton Court Flower Show is open today from 10am to 5.30pm. Trains to Hampton Court run every half-hour from Waterloo.
Unwins of Histon, Cambridge (01223 236236), sold nearly 200,000 packets of their patio vegetable seeds this season. Here are the varieties in the range, in order of popularity.
OUTDOOR CUCUMBER Burpless Tasty Green (Fl Hybrid)
TOMATO Tumbler (Fl Hybrid)
STRAWBERRY Temptation (Fl Hybrid)
MINI-COURGETTE Raven (F1 Hybrid)
SPRING ONION Ishikura
LETTUCE (Butterhead) Dolly
LETTUCE (Iceberg type) Malika
DWARF PEPPER RedskinReuse content