How Big Do San Marzano Tomatoes Grow

San Marzano, a treasured fruit among pizza makers, is a plum tomato originating from a small town called San Marzano in Italy. It’s an open-pollinated, heirloom variety, so the home gardeners can easily save seeds year after year to breed plants true to type. 

Besides their oblong shape instead of the typical round tomatoes, it’s the superior taste and texture that makes San Marzano easily stand out among other tomatoes. The flesh is thicker and has fewer seeds, while the taste stronger and sweeter, and with lower acidity than other tomatoes. 

Before growing the gold standard tomatoes for pizza sauce, you may have some questions in mind. A common question that gardeners ask is how big do San Marzano tomatoes grow? So let’s find out!

How Big Do San Marzano Tomatoes Grow

What’s the Mature Fruit Size?

San Marzano produces narrow, elongated fruits that can grow to about 4” long and 2” wide. They are borne in clusters of 6 to 8 on the vines, with each fruit weighing around 3.9 ounces on average. Some fruits may even grow to 5 ounces. The fruit is meaty and flavorful. The dense texture makes it a chef’s favorite for sauces, pastes and purees. 

How Many Tomatoes Does A San Marzano Plant Produce?

San Marzano plants typically produce a heavy crop, if given optimal care. Under ideal conditions, you can expect a yield of around 20 pounds of tomatoes per plant. If you assume an average weight of 4 ounces per fruit, this amounts to about 80 tomatoes from a single plant. 

What’s the Mature Plant Size?

San Marzano are indeterminate tomatoes that typically grow to a height of 5 feet. If you have a long warm growing season, they can even grow higher until the onset of the cold weather kills the vine. Though the heirloom San Marzano is indeterminate, determinate hybrid varieties are also available. These hybrids have a shorter, bushier growth and typically stay below 5 feet. The golden San Marzano hybrid is an excellent choice for container growing since it does not grow beyond 3 feet tall. 

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Does San Marzano Need Staking?

The true heirloom varieties are indeterminate vines and produce a heavy crop. They will need staking to carry the weight of fruits and the vine itself. Staking also keeps the plant from touching the ground, lowering the chances of catching soil-borne diseases. Continue tying the plant to the stake as it grows to provide continuous support as the height progresses. 

How To Space San Marzano Plants

Properly spacing San Marzano plants ensures that they can grow optimally, without competing for space, light, water and nutrients. It gives the vines a chance to grow freely and produce the biggest crop that it’s capable of. Preventing overcrowding of plants also minimizes the risks for diseases and pest infestations. 

Allow a minimum distance of 30 to 48 inches between plants if you’re growing the heirloom indeterminate variety. For determinate San Marzano hybrids, a spacing of 2 inches is sufficient. If you have a big crop that you’re growing in rows, allow a minimum of 3 to 4 feet row spacing to make it easier to walk between the plants for care during the season and harvest.   

Planting San Marzano From Seeds

When growing from seed, San Marzano are typically started indoors 6 to 8 weeks before the last frost of spring. Plant the seeds ¼ inches deep in the soil in a seedling tray. Use a sprayer bottle to mist the soil until it’s just moist. Place the tray over a heat mat to maintain a temperature of around 75°F. At this temperature, it can take anywhere around a week to ten days for the seeds to germinate. 

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Once the seedlings set their first set of true leaves, transplant them into 4-inch pots burying the stem in the soil to just below the leaves. Burying it deeper into the soil than its original position helps develop stronger roots for the plants. Fertilize the seedlings with a diluted dose of a balanced fertilizer every week or so to help them grow optimally. 

The seedlings are ready to go in the garden a week after the last frost of spring, once the nighttime temperatures stay consistently above 50°F. When planting the seedlings in the ground, bury the stems into the soil upto the first set of leaves. This will help develop an even stronger root system. 

Water deeply just after planting and maintain a regular watering schedule throughout the growing season. Place stakes next to each seedling at the time of planting them in the ground and tie the stems to the stakes as they grow taller.

How To Grow San Marzano Plants

Besides the superior taste and unique look, San Marzano grows just like any other tomato. It’s no harder to plant or to grow than the regular tomatoes. They grow through the summers, setting fruit until killed by the frost, just like the rest of the indeterminate varieties. Since they are not hybrids, you can save seeds each year to grow San Marzano each season and continue enjoying the same great flavors. 

Keep the plants well-watered through the growing season, especially in hot, dry weather. Other than fertilizing it at planting time, you’ll need to fertilize a second time as soon as fruits start developing. Choose a low-nitrogen, water soluble fertilizer to feed the plants and continue applying it each week until the fruit ripens. 

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Conclusion

So you know how big do San Marzano tomatoes grow. Other than the variety’s own traits, the size of the plant, fruit size and yield also depends on the climate, growing conditions and the level of care you provide them through the growing season. Give them good care and they’ll give you the best tomatoes for all your sauce, pasta and pizza recipes.

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