Solanum lycopersicum.

The most famous sauce tomato in the world, and the only one officially permitted on a true Neapolitan pizza. San Marzano comes from the commune of San Marzano sul Sarno, in Campania, in the volcanic soils laid down at the foot of Vesuvius — a light, mineral, exceptionally free-draining earth to which a good part of the variety's reputation is credited. It has been officially recognized since 1926, and the version grown in its zone of origin now carries a protected European designation. Italians class it among the pomodori pelati, the peeling tomatoes, and that's exactly where it excels.

Elongated fruits shaped like a stretched plum, carried in clusters on a vigorous indeterminate plant. What sets it apart comes down to four things: thick dense flesh, very few seeds, low water content, and mild acidity. The concrete translation in the kitchen: the sauce reduces much faster because there's less water to evaporate, it stays red and bright instead of turning brownish, and it doesn't need sugar to balance the acidity. The skin comes away practically on its own after thirty seconds in boiling water, which makes canning noticeably less tedious. For a marinara sauce, a passata, jarred tomatoes for winter or a pizza, it's the reference.

Grower's tip: dense-fleshed tomatoes like San Marzano are particularly prone to blossom-end rot, the famous black bottom — that brown, leathery patch that appears at the tip of the fruit. It isn't a disease and it's almost never a lack of calcium in the soil: it's a calcium transport problem, caused by abrupt swings in moisture. The plant dries out, then gets a lot of water at once, and the calcium doesn't reach the end of the developing fruit. The fix comes down to two moves: good mulch at the base and regular rather than heavy watering. Start indoors 6 to 8 weeks before last frost, sturdy staking and regular suckering — it's an indeterminate that climbs all summer.

• Open-pollinated. Italian heirloom variety recognized since 1926. Self-pollinating, low crossing risk.
• Indeterminate plant, sturdy staking and suckering useful.
• Matures in ~85 days.
• Exposure: full sun, sheltered from wind.
• Rich, deep, very well-drained soil. Space plants 60 cm apart. Mulching strongly recommended to stabilize moisture and prevent blossom-end rot.
• Start indoors 6 to 8 weeks before last frost. Transplant once all frost risk has passed and the soil is at least 15 °C.