Red alert: A trip to southwest France led Anna Pavord to discover some wonderful-sounding tomatoes, but nothing beats our very own varieties

Assier, just northwest of Figeac in the wide, empty spaces of the Causse de Gramat in southwest France must have once been an important place. Five roads lead into it. 'Assier' says the welcome sign. 'Son château. Son église.' I like that proprietorial 'son'. We don't have anything in English that assumes ownership in quite the same way. But without Galiot de Genouillac, François I's artillery chief, Assier would not have either its Renaissance château or its church. He built both, which must be why the frieze running all round the outside of the church is so unrelievedly martial, not about turning the other cheek. Cannons rule.

Driving through recently, on a visit to my brother, the usual sign was joined by another: 'Foire aux Fleurs.' I thought that might mean a flower festival in the church, which we've never yet been able to get into. It's always locked. But the sign was actually advertising a plant sale. The sloping green in front of the church was full of stalls. It was bedding out time in France: geraniums, geraniums and more geraniums. Enchanting. Most of the plants were unloaded from the backs of old 2CV Citroën vans and after a brief breath of fresh air were bundled back by their new owners into different 2CVs.

There were plenty of young vegetables on sale too: different salad crops, courgette plants, cucumbers, cabbages, sweetcorn. One stall was packed with nothing but tomato plants - 40 different kinds. Slowly, I worked my way down the lines reading the handwritten labels. Very few were familiar. Carefully composing a sentence in my best French, I asked the young guy in charge which varieties had the best taste. He looked at me with the disdain particular to the French when dealing with the English and said 'Madame, they ALL have the best taste.' Why grow a tomato that doesn't have a brilliant flavour and tang?

So I bought a couple of 'Peche des Jardins' and a couple of 'Noire de Crimée' for my brother's garden, where I had spent some time weeding the veg patch. I can't find either in the catalogue produced by Simpson's Seeds, which lists more tomatoes than any other I know. 'Noire de Crimée' though will probably turn out much the same as the tomato we know as 'Black Krim' or 'Black Russian'.

In an ideal world I would be picking our first tomatoes just the day after I'd used the last of the previous year's crop from the freezer. That's happened only once. This year I've run out already and there's probably two months to wait until we start picking our own again. I grow tomatoes outside, so you can't be in too much of a hurry to get plants in the ground. Traditionally, the end of May was reckoned the safe time. Because of where we live, I risk planting out at the beginning of May. There are already good trusses set on 'Black Cherry' (newly introduced this year by Thompson and Morgan 99p) which I've not grown before, and 'Tres Cantos' which I know absolutely nothing about. I bought the plants from a local nursery just because I liked the names. Well, the strategy works when I back horses running in local point-to-points. Betting on names gives as many winners as reading the form book.

Traditionally in this country, tomatoes have been greenhouse plants. But given some luck with the weather, they grow well outside. Last summer was a cracker and we had great crops, particularly from the bush variety 'First in the Field' (Simpson's Seeds £1.50). 'Red Alert' (Thompson and Morgan £2.29) is also a reliable cropper. It's early enough to escape blight, the biggest problem if you grow tomatoes out of doors.

Blight is a fungus, a kind of phytophthora, which infects the leaves and fruit of tomatoes. The same blight can affect a potato crop. It is worse in a damp summer than a dry one, as the spores are carried in on the wind but need a moist surface area to catch hold and do their damage. Brown patches develop on the tomato fruits and the edges of the foliage. It looks a bit like frost damage, but you get that at the beginning of the tomato-growing season. Blight develops later in summer.

You can spray with a copper-based fungicide or with Dithane 945, which contains mancozeb, but these are preventative sprays, not curative ones. You have to start spraying as soon as the first fruits set and go on spraying every two weeks to the end of the season. I've never bothered. The best way of avoiding blight is to grow fast-maturing varieties such as 'Red Alert' and 'First in the Field'. Small tomatoes ripen more quickly than big beefsteak types. And if you grow potatoes, set your tomatoes as far away as possible from the potato patch. Potatoes, with their big leafy stems, catch the blight quicker than tomatoes and then pass it on.

It's too late to sow tomato seed now, but there are still plenty of tomato plants available in nurseries and garden centres. Check whether the plants you buy are cordon types or bush. Cordon tomatoes need to be trained up a tall cane and tied in at regular intervals. Pinch out the little shoots that develop in the leaf axils, otherwise the plant will waste its energy producing leaf rather than flowers and fruit. Bush tomatoes do not develop on long single stems but splay out into low mounds of growth. You just plant them and let them go. They are incredibly reliable and easy, though the fruits are closer to predatory slugs and snails.

Plants need watering in well when they are first set out, whether you plant them in pots, Gro-bags or the open ground. But once they have settled and are growing away, you shouldn't water too much. Studies at the National Vegetable Research Station at Wellesbourne, Warwickshire showed that overwatered tomatoes (and sweetcorn, French beans and runner beans) produce leaf at the expense of fruit. It dilutes the flavour too. Hold off until the plants begin to flower, then start watering again.

And when, at the end of the summer, you freeze your surplus, don't skin them. Bag them up in kilos, just as they are. They stay whole and separate like marbles rolling round in a bag. This is a huge advantage when you want to use them. You do not have to hack and bash away at a solid frozen mass to extract what you need. When you run the frozen tomato under a cold tap, the skin just drops off like silk. The shape doesn't stay of course, but the flavour seems unimpaired, perfect for sauces and soup.