How to grow San Marzano tomatoes from seeds

Written by heather lacey
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How to grow San Marzano tomatoes from seeds
San Marzano plum tomatoes are ideal for tomato-based sauces. (Brand X Pictures/Brand X Pictures/Getty Images)

San Marzano tomatoes are recognised around the world as one of the best sauce and paste tomatoes. Native to Peru, this heirloom tomato was brought to Europe in the 16th century and is grown in Naples, Salerno and Avellino in the Campania region of Italy. Although most of the commercial production occurs in Italy, San Marzano seeds are available in seed catalogues for cultivation by home growers.

Skill level:

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Things you need

  • Peat pellets
  • Tray
  • Cling film
  • Peat pot
  • Compost
  • Lime
  • 45 litre (10 gallon) planter
  • Tomato cage
  • Tomato fertiliser

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  1. 1

    Purchase San Marzano tomato seeds from a reputable online dealer or seed catalogue. Ensure that your seeds will arrive six to eight weeks before your region's last spring frost to allow time to grow transplants indoors.

  2. 2

    Soak peat pellets in water until they expand to about three times their dry size. Place one seed 6 mm (1/4 inch) deep in each pellet.

  3. 3

    Place the peat pellets in a tray, and cover them with cling film to create a miniature greenhouse. Put the tray near a south-facing window where it will receive full sunlight. Water the pellets when they appear dry.

  4. 4

    Transfer the seedlings to peat pots when they are about 2 weeks old. Plant the seedlings so their lowest set of leaves is just above soil level. Deep planting promotes strong root development.

  5. 5

    Water seedlings every other day until they are 6 weeks old. At 6 weeks, bring the pots outside for a few hours each day to harden them against winds and direct sunlight.

  6. 6

    Combine even parts soil and compost with 225 g (2 cups) lime in a 45 litre (10 gallon) planter. Transplant the seedlings so their third set of true leaves is above the soil, and place the planter in a location that receives full sunlight. Place a cage around the seedlings to support them as they grow.

  7. 7

    Water daily, and fertilise weekly. Tomatoes will be available for harvest in 78 to 85 days.

Tips and warnings

  • Drill holes in the bottom of the peat pot and planter pot to provide good drainage.
  • Use a pH test strip if you are unsure of soil acidity after combining soil and compost. The ideal pH range for tomatoes is 5.8 to 7.
  • Bring the planter indoors when nighttime temperatures drop below 12.8 degrees C (55 degrees F).
  • Prune the plant when it reaches 60 to 90 cm (2 to 3 feet) in height.

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