Heirloom tomatoes are old-fashioned varieties that you might not find on supermarket shelves. But organic farmers in Northern California (and elsewhere) have re-discovered many heirloom varieties---some are offered at farmers' markets and specialty stores. Heirlooms don't always look as uniform as newer hybrid types of tomatoes and they might not store or ship as well, but you will probably agree that their taste is second to none.
Black Krim Tomato
The Black Krim tomato originated on the island of Krim on the Black Sea, which is west of Russia and north of Turkey. It is such a deep red its color is almost chocolate, and the taste creates fans of all who try this one. One farmer in California grows this variety and sells it at farmer's markets.
The Brandywine tomato comes from The Amish farmers on the East Coast of the U.S. It has gained popularity in Northern California for its large size, up to one pound, thin skin with a pretty pink color and "old-fashioned real tomato flavor" that balances acidity with sweetness, according to Seasonalchef.com. Large beefsteak-type tomatoes such as the Brandywine need a long, warm growing season to ripen and do best in inland Northern California gardens.
The Stupice tomato is a prolific, early fruiting heirloom tomato from Czechoslovakia. The taste is considered "exception," according to the Seeds of Change Web site (see Resources). This is a good tomato for slightly cooler, foggy areas of Northern California because it begins to ripen earlier than some other tomatoes.
Green Zebra Tomato
If you want an unusual looking tomato, the Green Zebra is the one to choose. It scares some traditional tomato lovers off with its yellow-green color when ripe, but its flavor is "bright and acidic," according to Seeds of Change. The fruits reach four to six ounces and the plants produce large numbers of this unusual tomato. You'll know when to pick Green Zebras when they lose their shiny green color and become more yellow, almost in stripes. Green Zebras also perform well in Northern California's fog belt.
Amish Paste Tomato
A meaty tomato with little watery juice, the Amish paste is a good choice for a smaller, Roma-type heirloom tomato in Northern California. The plant produces an abundance of red, pointed 10-ounce tomatoes with few seeds and a good tomato taste that works well in sauces and salsas. The Amish paste tomato doesn't ripen as early as some of the other cherry and paste types, but if you want to make spaghetti sauce or salsa, this is a good choice for inland gardens in Northern California.