DOTT, PA. -- There is a tomato patch, purposely planted in a low-lying place to collect moisture, that has bedeviled the farmer all year long.

Healthy seedlings were transplanted in May, appropriately spaced in long rows that were appropriately separated, and then shrouded with a heavy straw mulch to hold in the damp and choke out the weeds.

For reasons unknown to the farmer, the tomato patch went berserk. The plants became huge, creating a thicket that covered the walkways and made passage nigh impossible. Billions of tomatoes seemed to form on the vines -- large, well shaped and, as it turned out, tasty.

The picking was difficult, but this patch was a success. Except for one thing. One of the four varieties of plum tomatoes in the field set almost no fruit. And to this day, the fruit that did form has failed to ripen.

It is a mystery for which the farmer has no explanation but for his partner's plausible theory that the intense heat of July probably fried the plants' flowers just as they would have begun forming fruit.

Puzzles of this sort arise routinely in the truckpatch. In fact, so confounding are the ways of nature that a day rarely passes without the farmer realizing how little he knows about his craft.

This benightedness, however, is not perceived by most of the customers at the urban markets who blitz the farmer with questions about his wares and about the problems in their own gardens. They imbue the farmer with undeserving omniscience.

Truth be told, however, the benightedness is not limited to the truckpatch. There was a time when just about every city dweller had a tie to the country -- a relative, or whatever -- that provided at least a cursory understanding of the source of our food.

People knew, for example, that a chicken planted upside down would not grow. They knew that milk did not come from a stockroom behind the dairy counter. They knew the difference between sweet corn (for people) and field corn (for animals).

Today, the city's ties to the country are more tenuous, and so apparently is the understanding.

One of the farmer's favorites was a woman who stood before his flower display at the Columbia market and quizzically eyed a bucket of cockscomb, a large burgundy flower that resembles an oversized brain.

She called the farmer over and asked, almost under her breath, "Is this a vegetable or what? How do you fix it?" When told that it was actually a flower that would dry and keep for months, she bought three stems and seemed pleased about it.

Another woman pondered the bunches of dried statice, made a choice and moved tentatively to the counter. "Is this flower dead?" she asked, with a twinge of pain and hurt in the voice. It was a hard question to answer.

On a recent Sunday at Takoma Park, a serious young man picked up a red pepper and then leaned forward with a question. "Why is this so shiny," he asked. "Because I buffed it all night," the farmer answered playfully, although in actual fact each of the peppers is wiped free of field dust before it goes to market.

A corollary question comes up repeatedly. A customer will survey the flower and vegetable display and then ask, "Why do your things look so colorful?" The farmer almost always responds that he uses a lot of spray paint, an answer that draws an understanding chuckle.

Vegetables, of course, come in many colors, and the farmer gets a perverse sort of pleasure from bringing in the offbeat things that are sure to provoke confusion and questions.

Just when the shopper learns that the Chioggia beet, with the bright red exterior, is not a radish, the farmer throws in a ringer. This fall, it's the Scarlet Ohno turnip, which gets confused with both a radish and the Chioggia beet.

Other items, such as the orange peppers, the burgundy snap beans and the purple cauliflower, never fail to stir the curiosity. They are grown not for the fun of it but because they taste good and they look good. Once tried, they usually are purchased again.

Another genre of questions is more challenging: "What does it taste like?" or "Which is the best tomato?" and "How hot is this pepper?" The farmer has a series of wiseacre replies ("Like a Snickers bar, only cheaper" or "Sort of like a shag carpet" or "Acidic, but not too acidic"), but the best answer is to offer a sample.

Once sampled, the little Yellow Doll watermelon, with its canary-colored flesh, became a best seller. The squatty-looking Jenny Lind melon, once tried, became a favorite. The Sweet 100 cherry tomato ("Better than an M&M") was a box office hit. Ditto the Chioggia beet, with its concentric red and white circles and fine flavor when eaten raw. Old-time tomatoes, sometimes misshapen and ugly, were a summer sensation after tasting.

So there are fun and games in the truckpatch and the farmer, despite his inability to solve many of the mysteries that confront him each day, feels a certain usefulness when he can explain how to cook a kohlrabi or how to use the fennel and the frying peppers.

He also has learned to be more patient with the trying questioners, such as the gardeners who insist in the spring on buying a plant that will produce a red pepper instead of a green pepper.

It probably wasn't all that long ago, the farmer reminds himself, that he didn't know that most peppers start out green, then ripen to red, gold, orange, purple or chocolate. Another of those mysteries.

Ward Sinclair is a former Washington Post agriculture writer who now farms a Pennsylvania truckpatch.