"The fruit is ready to harvest when it reaches about 15 cm (six inches) in length. For commercial use it is generally harvested no earlier than January when it is at optimum size. However, for ritual use it must be picked while still small in order to reach the market in time. The optimal size is also the best for marketability, as by growing larger it may lose some of its beauty. Since the citron blooms several times a season, fruit may also be picked during July and August, and even in June. According to Halacha[3] the fruit must only reach the size of a hen's egg in order to be considered kosher, but larger sizes are preferred as long as they can be held with one hand. Marketwise, a nice size fetches a higher price, so long as the fruit is also good in other aspects. If both hands are needed to hold it, it is still kosher, but less desirable. Moroccan Etrog with a prominent Gartel The etrog may differ in shape since several citron varieties are used for that purpose, each bearing fruits with a distinct form and shape. Furthermore, a specific variety or even a single tree may also bear fruit in several shapes and sizes. An etrog of completely round shape is not-kosher,[3] whilst a slanted or bent specimen is permissible but not the best.[3] The bearing branch must be arched down with care, in order to get the fruit growing straight in a downward position. Otherwise the body of the fruit will be forced into a downwards curve because of its increasing weight. The practice of arching the branch must be performed very delicately in order not to break the stiff citron twig. While many prefer the pyramid shape of variety etrog, and others prefer the barrel shape of the Diamante, some look for an etrog with a gartel—an hourglass-like strip running around the middle, more commonly found on the Moroccan citron. 6th century CE synagogue mosaic in northern Negev, Israel, depicting etrogs at the base of a Menorah According to researchers, this gartel indicates when the... more... - Spidra Webster from Bookmarklet

I've been sorta fascinated by this since I first heard of it. I was touring one of the largest citrus collections in the US and the owner said he'd had to fence off part of it because rabbis were actually trespassing and stealing some of the special citron varieties he had. I couldn't believe it! You're a religious leader and you're stealing?? Anyway, it's interesting the ritual place this fruit has taken and not just any fruit but particular specimens of particular varieties. - Spidra Webster