The joy of eating cherries derives, of course, from the serious business of growing them. Jim Nugent, a scientist at Northwestern Michigan Horticultural Research Station, in Traverse City, is an expert on the matter. During my trip, I stopped by his office to learn more about commercial cherry farming, which can apparently be a trying endeavor in many ways. First, Nugent explains, it's expensive, and it requires a major commitment: a cherry tree, whose average life span is 30 years, takes about seven years to bear fruit. (By comparison, an apple tree takes three years; the life span of most apple trees is similar to the cherry's.) Then there are the diseases particular to cherry trees, which are difficult to control, like cherry leaf spot, in which a fungus infecting a single leaf may inhibit the ripening of an entire tree. Diligent pruning is also a must: Cherry leaves are plentiful and can block sunlight in a way that prevents the fruit from ripening. The harvesting of sours is perhaps the easiest part of raising the fruit; it is usually done by a long-armed machine that grabs the base of each tree and shakes it until the ripe fruit falls onto a "catching frame" (which resembles a tarp shaped like an upside-down umbrella) spread on the ground or, sometimes, attached directly to a tree. Sweet cherries for the fresh market are generally harvested by hand, but in Michigan more than 90 percent of the sweets grown are sold to processors; those too are mostly harvested by mechanical means.