How to Grow and Care for a San Marzano Tomato Plant

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 six to eight, each about 4 inches long. These plants prefer full sun and do best with consistent moisture. The vines can reach 6 to 8 feet tall when mature. Note that the green part of the plant is toxic to pets. Read on for our care guide.

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.

How to Plant San Marzano Tomato

Transplant San Marzano 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

These are the main care requirements for growing San Marzano tomatoes:

• Place near a wall or fence or offer them a stake or strong cage for extra support
• Prefers full sun
• Likes consistent moisture
• Does best in temperatures between 50 and 95 degrees Fahrenheit

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': These 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': This 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': This plant was developed in Italy to produce rather abundantly and resist cracking in wet weather.
• 'San Marzano Gigante 3': A variety that produces larger 2-and-a-half-inch fruits later in the season, about 90 days from the planting date.
• 'San Marzano Scatalone': A plant that produces later in the season, offering fruits that are more pear-shaped.
• 'San Marzano Lampadina': A variety that is quite rare and vigorous, giving way to elongated pear-shaped tomatoes with fleshy walls and hollow seed cavities.
• 'Pink San Marzano': This variety produces sweet pink fruits quite heavily.
• 'San Marzano Nano': This 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': These 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.

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.

Propagating San Marzano Tomatoes

San Marzano tomatoes can be propagated via cuttings. Here's how:

1. Cut a 6-8 inch branch from a healthy plant and trim back lower branches or anything that is yellow/browning.
2. Place the end of the branch in a cup of water.
3. Place in indirect light. such as by a window.
4. Once a root ball forms (generally in a few weeks), remove from the water, plant in a container, and stake for support.
5. Keep cool in indirect light and keep the soil moist for a few weeks.
6. When you see new growth, transplant into the garden in full sun.
   

How to Grow San Marzano Tomatoes from Seed

Here's how to grow San Marzano tomatoes from seed:

1. Using a rich potting soil, 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.
2. 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.
3. 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.
4. When a good set of "true leaves" has 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.
5. As seedlings grow, water them whenever the top inch of the soil becomes dry.
6. 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.

Potting

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.

Common Pests & 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.

Common Problems With San Marzano Tomatoes

Yellowing Leaves

Yellowing leaves on a San Marzano tomato plant can indicate a nutrient deficiency, generally nitrogen. Fertilize with a nitrogen-based fertilizer to help reverse the yellowing.

Not Producing Fruit

If your San Marzano tomato plant is not producing fruit, it could be an issue with light. These plants need six to eight hours of sunlight per day. Without adequate light, they won't produce fruit.

From: thespruce