The perfectly red-ripe tomato is a touchstone on many levels: a harbinger of the summer season, an exemplar of heirloom quality, a triumph for the backyard gardener. Papa said there’s only two things that money can’t buy, and that’s true, true love and homegrown tomatoes.
So why bother with green tomatoes? One answer is that they, too, are harbingers of a new season—fall. Tomato vines will put on more fruit than the waning sun will ripen. The first freeze abruptly ends the crop in many parts of the country, but even in frost-free Southern California, cooler nights and overcast days mark the end of red tomatoes. In their immaturity, green tomatoes are zingy and firm. They’re good for chutney, pickles and relishes.
And if you're from the South, green tomatoes may also mean chow-chow.
See here for more information about this wonderful catchall relish, including a recipe—with warm thanks to WNYC for the enjoyable interview.