San Marzano Tomato Seeds

Start San Marzano Tomato seeds indoors 7–9 weeks before your last expected frost. Sow about ¼ inch deep in a seed-starting mix and keep soil consistently warm. Under the temperature 70–85°F heirloom San Marzano Tomato seeds germinate in 7–10 days. Once seedlings have their second set of true leaves, move them to individual 3–4 inch pots. Before transplanting outdoors, harden off the seedlings for 7–10 days. For that, set them outside in a sheltered spot for a few hours each day, gradually increasing exposure. 

San Marzano Tomato plants need full sun — at least 6–8 hours of direct light per day. They can manage in shadier conditions, but fruit set drops off noticeably. Soil should drain well, but retain moisture, so sandy loam with pH of 6.2–6.8 suits the best. Work in compost before planting to make the soil fertile. Water regularly and consistently. It’s better to water more frequently, that letting the soil dry out between waterings, then soaking it.

Space plants 18–36 inches apart, with 36 inches between rows, and put in cages or a trellis at planting time. Prune suckers (the shoots that grow in the crotch between stem and branch) every week or two to keep the plant focused on fruit production. When transplanting, bury the stem deep to get a stronger, more drought-tolerant plant. Apply fertilizer when the first fruits start to set. Fruits are ready to pick when they're deep red and give just slightly under thumb pressure. It happens usually in 78–85 days from transplant.