Postcard from... Jerusalem

To an outsider, it is one of the more bizarre aspects of Judaism: the annual selection of the etrog, a lumpy-looking citrus fruit that is required for Jewish rituals.

In the runup to Sukkot, the week-long religious holiday that began on Sunday, Jews throng Jerusalem's central market in search of the perfect etrog.

It is just one of the so-called "four species" that will be waved during the week's ceremonies, the other three being a palm frond, a myrtle branch and a willow branch. Together, they symbolise the unity of the Jewish people.

With magnifying glasses, religious men huddle around tables of etrogs, scouring the citrus fruit for blemishes, however tiny. The ideal etrog should be yellowing, not green, and there shouldn't be any black marks or holes on it.

Perfection does not come cheap, and the best specimens can fetch hundreds of dollars, not just in Israel, but in America's thriving Jewish communities.

For the fruit farmers, it is something of an art to grow the perfect etrog, the finest of which are said to come from the Calabria region in Italy. The tree is reputedly weak, and Israeli farmers often hire extra workers around the clock just to guard the fragile fruit, preventing it from snagging on a thorn, for example, during the short growing season.

It is a costly business in a country where the etrog has limited appeal outside of the religious holiday. After all, typically less than half of the farmer's crop will make the final cut.