Jose Gandia produced his first peach of 1993 on 18 March - the earliest that season to be grown entirely outdoors. But he was too ambitious: late frosts eventually put paid to his tentative crop.

This year Mr Gandia, whose family firm, S A T Royal, is Spain's largest producer of hand-picked peaches and nectarines, was more conservative: his first fruits were ready for market on 10 April. That is still a huge achievement; ripe peaches and nectarines are not usually available until at least the beginning of June. Mr Gandia has extended the European growing season by six weeks.

To judge by the supermarket shelves, we now have summer all year round. In the depths of British winter we can buy nectarines which have been flown half- way round the world. They usually cost a bomb and taste of very little. But when I visited Mr Gandia's orchards outside Seville in the Guadalquivir river valley, earlier this month, I found that his fruits were truly luscious. Yellow peaches and nectarines named 'Candor' and 'Sun Red' - sweet but refreshingly sharp, wonderfully juicy - were just giving way to 'Springcrest' and 'Red Diamond', and to white varieties such as the 'Robin' peach, and a stunning, perfumed nectarine called 'Silvery'. How is this achieved?

Jose Gandia is a specialist, who took the decision not to extend his range,

but to concentrate on nectarines and peaches. This meant becoming involved with research, most of which is carried out in the US. 'Ever since the end of the Second World War,' says Mr Gandia, 'America has led the way in this field, but there has been a problem for us Europeans. US consumers buy with their eyes on the cosmetic appearance of fruit, and most of the fruit that's sold never gets eaten. In the US they sell fruit that is not properly mature, and then handle it badly. Breeders would show me long lists of different factors for classifying fruit - colour, size, smoothness - but nowhere was there any mention of taste.'

So Mr Gandia decided to fund his own research at the University of Florida. Now he is growing 300,000 peach and nectarine trees, as well as his experimental 'collections' - sets of 2,000 different varieties bred especially for him. Each strain is tested on five different root stocks, and to taste the same variety of white peach from different root stocks is a revelation.

Once early varieties with powerful flavour have been selected and planted, vigilance is essential: sophisticated weather prediction equipment alerts managers to late frosts, and fires are built to prevent damage to the crop.

We can buy these fruits in Britain at Marks & Spencer, which is placing 'tree- ripe' specimens on its shelves within three days of picking. 'We've done a lot of work in the south of France on this high-risk ripe fruit,' says Peter Village, M & S's fruit technologist. 'Their season begins in June. But because Seville is that much farther south, we can produce the same quality of fruit between March and June, when the southern hemisphere sources are past their best.'

Summer stone fruit is still basically a bulk market, and price is the main factor. Growers strip their trees in one or two pickings. Because the fruit is graded by machines, it has to be picked when relatively green and 'backward', which means that much of it never ripens properly. And crews are often paid solely by the quantity they pick.

Mr Gandia's exports to M & S are treated quite differently. The fruit is picked only after it has passed two sophisticated maturity tests - one to judge sugar content, the other resistance to pressure. 'This tells us that the fruit, although firm, is mature and can still ripen en route to stores,' says Mr Village. In Mr Gandia's orchards, the pickers receive 'ripeness' bonuses. Each pallet, tested as it is picked, must contain at least 8 to 12 per cent overripe fruit; without this margin of waste, the maturity of the rest cannot be guaranteed.

Further tests, for ripeness and pesticide residues, are carried out, before the fruit is graded by size and quality, and carefully packed.

Among European countries, Spain has a relatively poor reputation for pesticide control. So is Mr Gandia's early harvest predicated on chemical treatments? 'A mistake with pesticides would be Chernobyl for us,' he says. 'Unlike smaller farmers, who sell their fruit into co-operatives where their production is swallowed up in a larger pool, a pesticide problem would close us down. We are using about one-third of the chemicals we did 10 years ago.' According to M & S, daily tests never detect any chemical residues - not even those within 'safe' government limits.

The chance to buy ripe peaches and nectarines with a clean bill of health, early in the season, is good news for

British consumers. And now that Marks & Spencer has loose fruit displays in 57 of its stores, with a further 80 to follow next year, those of us who like to sniff out ripeness may be so attracted by the perfume of the fruits, we will buy them in Continental fashion, by the kilo.