Heirloom tomatoes are renowned for their amazing range of flavor, color, shape, suitability for specific growing conditions, and true-to-parent seed saving ability. Below is a photo of the queen of heirloom tomatoes: a ripening Brandywine. Brandywine tomatoes are too big and odd-shaped to be of interest to commercial growers. But their awesome flavor has made them favorites of gardeners everywhere, and they are one of the best reasons to get into vegetable gardening. Biting into a Brandywine or other heirloom tomato is an experience you can't buy from the grocery store.
To be considered an heirloom, a tomato variety must be open-pollinated and have been grown true-to-parent for at least 50 years. This means that when pollinated by itself or another of the same variety, the seeds will grow into tomatoes with exactly the same qualities as the parent.
A hybrid plant does not do this – each generation is a man-made cross between different varieties, and its seeds will not be “stable” or grow the same as the parent. Heirlooms have been grown and kept pure for many generations by loving caretakers. You can save your own seeds from heirlooms and plant them again next year, forever. (Provided they haven’t cross-pollinated with other varieties)
Hybrids were developed from heirlooms in order to enhance specific qualities, such as disease resistance and commercial and shipping benefits. This not a bad thing, it’s just that these might not be the same qualities that you as a home gardener are looking for.
Heirloom tomato varieties may be determinate, meaning they grow to a certain size and then produce their crop of fruit, or indeterminate, meaning they keep on growing, sprawling and producing fruit forever (or until killed by frost).
Some Classic Favorite Heirloom Tomatoes
Beefsteak Varieties (meaning a single slice fills a hamburger bun)
Cold Tolerant/Early Season Varieties
(not hardy, just do well in San Fran summers)
Here are some links to seed catalogs that have a lot more information on heirloom tomatoes:
Gary Ibsen’s Tomato Fest Catalog The best and most comprehensive information you’d ever want to know about heirloom tomatoes, as well as a great place to order seeds. It's an online-only catalog.
Johnny's Selected Seeds These guys have heirlooms of lots of different vegetables, including tomatoes.
Seed Savers Exchange We are all indebted (whether we know it or not) to the wonderful committed gang over at Seed Savers Exchange. These folks have collected, grown, and saved many of the world’s precious heirlooms from extinction. (And they have the most beautiful gardening calendar, as well as catalog, ever.)