All tomatoes are green when immature, but a few varieties remain green when fully ripe. Martha grows green tomatoes in her garden every year, both for their luscious flavor and unique look -- she surprised guests at a luncheon last fall with BLT's made with green tomatoes and red lettuce.
Green tomatoes range in size from large beefsteak varieties such as 'Aunt Ruby's German Green' to 'Green Grape,' an egg-shaped cherry tomato with pale golden-green skin. One source with a wide variety of green tomatoes is Burpee Heirlooms in Warminster, Pennsylvania. It offers seeds, as well as four varieties of green tomato plants. Other sources for green tomatoes include Tomato Growers Supply Company, and the Cook's Garden.
And, just in case you were wondering, the traditional dish of fried green tomatoes is made from common red tomatoes picked while they're still green. They are harvested when half-ripe so that they are still firm enough to hold together when fried. It's the texture and size, rather than the color, that is most important for frying. Medium-sized tomatoes are best; larger ones tend to fall apart when you flip them.