You say tomato, he says jam

I don't generally put sugar on a tomato. It doesn't seem right, somehow. As a child, though, I knew an adult who routinely sugared tomatoes and survived. In fact, she positively promoted the idea, as if the rest of us were missing something special. But I was (then) too conservative to try such an outrageous idea.

It also now emerges that my wife's mother enthusiastically dipped her tomatoes into a small mound of sugar before popping them in her mouth. Her children have for some reason not perpetuated the tradition.

But why not?

The trouble is, tomatoes are confused. They don't really know if they are fruit or vegetables. Not all vegetables are leaves or roots, of course. Some are seeds. Some are flower buds. Some are stems, some bulbs, some pods.

But the ones that are, from a botanist's point of view, technically fruit, rarely remind us of this fact by means of sweet flavor or some other kind of indisputably fruity sign.

I mean, who thinks of an eggplant (or, more prettily I think, aubergine) as a fruit? Or a zucchini? Or a pepper? Yet fruit they are. So are cucumbers. And tomatoes.

Which is why, when I received a fax from a friend asking if I had ever tried "red tomato jam," I shouldn't logically have winced at the very thought.

I sprinkle red tomatoes with salt and pepper. I like them vinegary in the form of ketchup. They seem perfectly at home with anchovies or pepperoni on a pizza. Tomato juice should definitely be spiced with Worcestershire sauce. What I do not do with tomatoes is add them to fruit salads (though, paradoxically, a few slices of cucumber do add something indefinable and marvelous to a fruit punch).

Yet, viewed without educated preconceptions, tomatoes are the fruitiest of fruits. They squish and squash like fruit. Their excessive juiciness once the skin is broken argues strongly for their fruitiness. They hang on the vine in a distinctly fruity way, like oversize richly red grapes. When thoroughly ripe, some varieties taste - if you close your eyes and bury your bias - surprisingly sweet.

If a Martian were introduced for the first time, let us say, to a tomato and a banana (having previously been shown peaches, plums, and pomegranates as undeniable examples of fruit) and were asked which is a fruit, he would unquestionably reply "the tomato." What looks fruity about a banana?

It is a "concept thing."

It appears that tomatoes, in at least one large country that eats them by the zillions, were, in fact, once classified as fruit. Then they came up against the governmental tax people. In their wisdom they had decreed that fruit was not taxable while vegetables were. The Veggie Cage website tells it as follows: "Until the late 1800s, the tomato was classified as a fruit to avoid taxation, but this was changed after a Supreme Court ruling that the tomato is a vegetable and should be taxed accordingly."

In Britain (where I live), the tomato had rocky beginnings. Because it had connections to deadly nightshade (which lives up to its name), it was considered poisonous. So it was grown only for its good looks. It was a decorative houseplant.

We are well beyond that concept now, of course. But we are, all the same, universally convinced - for reasons that have, so far as I know, nothing to do with death or taxes - that this fruit is a vegetable.

In fact, the tomato is far more justifiably a fruit than, say, rhubarb is. I have a book simply called "Vegetables," and it includes both tomatoes and rhubarb. Of the latter it says: "Rhubarb is unusual among vegetables, since it is generally eaten with sugar." That's one way of putting it, I suppose. The other is to just classify it (as we all do) as "unusual among fruit, being a stem."

I had a phone call yesterday from Maria, who lives along the road. She wondered if our water had stopped, as theirshad. It hadn't, but I promised I would phone the supplier and ask what it was up to.

"Oh, by the way," I said, "your rhubarb jam was delicious."

"Was it as good as yours?" she asked. (I had given her the recipe.)

"Better," I said. I could tell she was happy to hear this. "Now I'll bring you a pot of my tomato jam to try," I added.

"Ooh, I'm not sure I'd like that," she said.

"You'd be surprised how delicious it is. It has a flavor all its own: very sweet, with a texture not unlike plum. And it looks astonishingly beautiful."

But I could tell she was struggling with the idea. I'm not sure I'll risk wasting any of it on her.