How to Grow a San Marzano Tomato Plant

san marzano tomato plant

Erika Edqvist / Getty Images

Native to Italy, San Marzano tomatoes can be identified easily by their oblong shape and pointed ends. Sometimes they are called "San Marzano sauce tomatoes," because they are fleshy and have fewer seeds than other kinds of tomatoes. Strong and sweet in flavor and less acidic, this old-fashioned tomato is a favorite snack of many gardeners. Fruits grow in clusters of 6 to 8, each about 4 inches long. Buy a plant from a local garden center. Or, if starting seedlings, sow seeds about 8 weeks before the last frost date and a little earlier than other tomatoes, because San Marzanos need about up to 85 days to mature on their vines, which can reach 6 to 8 feet tall.

Common Names San Marzano Tomato
Botanical Names Lycopersicon esculentum "San Marzano"
Family  Solanaceae (nightshade)
Plant Type  Annual vegetable plant
Size  6 to 8 feet tall, 2 to 3 feet wide
Sun Exposure  Full sun
Soil Type  Organic, well-draining
Soil pH  Acidic to Neutral
Bloom Time  Summer
Hardiness Zones  5-10, USA
Native Area  Europe
Toxicity  Plant is toxic; fruit is non-toxic

How to Plant San Marzano Tomato

Transplant seedlings when they are 6 to 12 inches tall. Establish them in a hole twice as wide and the same height as the plant. Set at least two-thirds of the seedling's stem underground and bury it. For stronger growth, dig a trench and bury the plant sideways, situating the tip above the soil surface. Then fill the hole with soil. Tamp the soil down. Water well. Space plants 30 to 48 inches apart. As each plant grows taller, tie branches with twine or strips of pantyhose.

San Marzano Plant Care

Place plants near a wall or fence or offer them a stake or strong cage for extra support. It's best to do this sooner rather than later while the roots are small. Otherwise, you may have to slide it over the tomato plant and disturb its growing foliage. Because most San Marzano tomatoes are indeterminate (and not a small bush determinate), typical cages will be too small. Choose one that is tall enough and strong enough to support the many tomatoes it will produce.

Light

San Marzanos prefer full sun, like all tomato plants. Plant them in a location that gets at least 6 to 8 hours of sunlight daily.

Soil

To make a rich soil for San Marzano tomato plants, mix 1/3 organic matter and 2/3 high quality organic soil, or mix together 1/2 regular top soil and 1/2 organic matter such as peat moss, manure, or compost. You can also mix in 1 to 2 cups of garden lime per 10-gallon container. Maintain a soil pH between 5.8 and 7. If needed, raise the pH level with wood ash or more agricultural lime, or lower it with organic matter.

Water

Tomato plants like to be consistently moist. Don't let their soil dry out completely. You can water them with compost tea (made by letting compost or manure sit in water for a while before mixing it). Use this, pondwater, well water, or rainwater to water plants well.

Fertilizer

Within two weeks of planting, use a 5-10-10 fertilizer, which is low in nitrogen, to fertilize foliage enough to keep the plant healthy and focus the nutrition on the fruit bearing. Apply fertilizer in trenches at least 6 inches from the plant's steps to avoid burning any leaves that are low to the ground. Use a water-soluble fertilizer for tomatoes grown in pots.

Temperature and Humidity

Grow San Marzano tomatoes outdoors in temperatures between 50 and 95 degrees Fahrenheit and in soil that is at least 60 degrees. Do not transplant seedlings or young plants in soil that is too cold, as their growth might be stunted by the shock.

Types of San Marzano Tomatoes

San Marzano plants come in many different varieties, ranging from the original heirloom plant to hybrids.

  • Heirloom "San Marzano" are sometimes called "San Marzano 2" or "San Marzano 3." These are the plants that make traditional oblong, thickly walled fruits with few seeds.
  • "San Marzano 15 F1 Hybrid" is one hybrid that was developed in the U.S., yielding larger pear-shaped tomatoes a little earlier in the season.
  • "San Marzano Lungo F1 Hybrid" was developed in Italy to produce rather abundantly and resist cracking in wet weather.
  • "San Marzano Gigante 3" produces larger 2 and a half-inch fruits later in the season, about 90 days from the planting date.
  • "San Marzano Scatalone" also produces later in the season, offering fruits that are more pear-shaped.
  • "San Marzano Lampadina" is one variety that is quite rare and vigorous, giving way to elongated pear-shaped tomatoes with fleshy walls and hollow seed cavities.
  • "Pink San Marzano" produces sweet pink fruits quite heavily.
  • "San Marzano Nano," a cultivar, makes a smaller plant that is considered determinate, growing to just a few feet tall and remaining small mid-season as it produces tomatoes that are cylindrical and flavorful.
  • "Golden San Marzano" plants are also determinate, growing 3 feet tall and bearing small plum-shaped yellow fruits.

Harvesting

Most San Marzano tomatoes will ripen 78 to 85 days after transplanting. When a fruit is big and still a bit green and yellowish, they are already ready for harvest. As with other tomatoes, they can continue to ripen even after they have been picked, or they can fully ripen on the vine. Gently twist the stem or use clippers to harvest. If you do harvest a tomato too early while it is still very green, store it in a paper bag and let it ripen for a few days.

Growing in Pots

Grow indeterminate (6 to 8 feet tall) varieties in pots that are at least 10 gallons in volume. Grow a smaller variety in a 5-gallon bucket. Make sure that there is ample drainage.

Pruning

When the plant grows to about 2 or 3 feet tall, begin pruning suckers. This will signal to the plant to send sugars and nutrients where they are most needed.

How to Grow San Marzano Tomatoes from Seed

Choose a rich potting soil for seed sowing. Fill a bucket with the soil and then water slowly and stir the water in. Allow the soil to become moist, not soggy. Distribute the soil into seedling trays and compact it with your fingertips, filling the trays up to 1/4 inch from the top. Sow one seed on top of each cell. Then sprinkle a little more soil to cover the seeds. Use a spray bottle of water on the soil to keep the surface moist. This top layer of moisture will maintain elevated humidity levels, while the bottom inches of already moist soil will encourage the seed to sprout. Other ways to maintain moisture and a high humidity level are to cover trays with plastic wrap, use a heating mat, and set a tray underneath to regularly fill water with. Place seeds in direct sunlight near a south-facing window or under a grow light. Maintain a temperature of 70 to 80 degrees Fahrenheit and check for moisture loss every day.

When a good set of "true leaves" have appeared, the seedling will be ready for transplanting into a 4-inch pot. Fill 1/3 of the pot with soil. Then cover the seedling with soil so that the leaves are 1/2 inch below the top of the pot. Tamp the soil down with your fingers. As seedlings grow, water them whenever the top inch of the soil become dry.

Transition plants from indoors to outdoors through the process of "hardening off." Depending on your area's frost dates, likely this can be done in April or early May. Begin transitioning seedlings on a sunny day with a low breeze. Set plants in the sun for a few hours during the warmest time of the day. Make sure they do not burn or get damaged. If stems need to be made stronger to withstand wind, run a fan on them indoors for about 1 hour each day.

Common Pests and Plant Diseases

Generally, San Marzano tomatoes are free from many pests. If pests such as aphids do come, use hot water or sticky strips to manage them. One disease to keep an eye out for is blossom end rot, which is caused by a lack of calcium in the fruit. Prevent this rot by adding crushed egg shells or lime to the soil.

FAQ
  • Are San Marzano tomatoes easy to grow?

    Yes, in the right conditions and with the right care, they grow quite vigorously.

  • How fast do San Marzano tomato plants grow?

    Depending on the variety, fruits will ripen and be ready for harvest within 75 to 90 days.

  • What is the difference between Roma and San Marzano tomatoes?

    While related to Romas, San Marzano tomatoes are bright red, more thickly skinned, and have fewer seeds.

Article Sources
The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Golden San Marzano (Rutgers NJAES).” New Jersey Agricultural Experiment Station.