The thick flesh and sweet, full-bodied flavor of the San Marzano tomato make it perfect for pastes and sauces – it’s little wonder many gardeners fawn over this heirloom variety!
This distinctive plum tomato has a lower seed count and boxier shape than you may be used to, but it grows much like other indeterminate tomatoes with the right care.
In this grower’s guide, I’ll help you locate the best San Marzano seeds plus provide step-by-step instructions on planting your tomatoes, care tips, and more.
San Marzano Tomatoes at a Glance
Popular San Marzano Tomato Varieties
Though its origins are unclear, the classic San Marzano tomato is thought to be an heirloom variety passed down through generations of Italian growers in the 19th century for its intense flavor.
A San Marzano tomato is typically 4-6 ounces and is characterized by a blocky oblong shape, rich taste, and thick walls lined with fewer seed pockets than regular tomatoes.
However, over the years many hybridized varieties have been produced that vary in shape, weight, weather resistance, and taste.
Here are 6 popular kinds:
- ‘San Marzano Nano’ – Dwarf variety, medium-sized cylindrical fruit, ideal for potted growth, stops growing mid-season, strong flavor, 2.5 ounces, matures: 70-80 days.
- ‘San Marzano Gigante 3’ – 7-inch fruit, robust flavor, meaty flesh, 7-14 ounces, matures: 90 days.
- ‘San Marzano Lungo F1 Hybrid’ – 4-inch fruit, deep-red skin, low water content, resistant to cracking, 2.4 ounces, matures: 75-80 days.
- ‘Pink San Marzano’ – Medium-sized fruit, pinkish-red skin, sweet flavor, juicy flesh, 3-4 ounces, matures: 70-80 days.
- ‘San Marzano 15 F1 Hybrid’ – Pear-shaped fruit, early yield, resistant to verticillium wilt and nematodes, 4 ounces, matures: 78 days or less.
- ‘San Marzano Scatalone’ – Large pear-shaped fruit, late-season yield, meaty flesh with rich flavor, 4 ounces, matures: 75 days.
Best Places To Buy San Marzano Tomato Seeds
Quantities: 250mg, 1oz, 4oz, 1lb, 5lb packs.
Offering both organic and open-pollinated seeds. Seed quantities vary.
Quantities: Sampler (~15 seeds) and Large (~80 seeds). Indeterminate.
San Marzano Tomato Seed Planting & Germination
Supplies:
- 3- or 4-gallon bucket
- 36-cell seed tray
- Spade
- Garden rake
- Rich potting soil
- Compost
- Heat mat
- Misting bottle
- 4-inch plant pots
- Jiffy 4-inch peat pots
- Support stakes
1. Prepare Suitable Soil in a Bucket 6-8 Weeks Before Last Frost
Around 6-8 weeks before the last local frost date, fill a clean bucket with rich potting mix that provides slow-release of nutrients, such as 1 part loam/coir to 3 parts potting soil.
Add a handful of organic matter such as compost to the soil. Slowly add water, and stir gently by hand until the soil mix feels moist but not soggy.
2. Fill Seed Tray Cells With Soil & Plant 1 Seed Per Cell
Empty the moist soil mix onto the seed tray making sure each cell is filled, and remove the excess – a good way to flatten down the soil in each cell is to gently push the bottom of a second cell tray on top of the soil to level it out.
Leave a ¼-inch of space below the rim of each cell and place one seed at the center of each cell. Cover each seed with additional soil.
3. Moisten the Tray & Place in Warm, Humid Conditions
Moisten the soil surface using a water misting bottle. Cover the entire tray loosely in clear plastic wrap to increase humidity.
Place the tray on a heat mat near a south-facing window, and maintain a temperature range between 70-80°F.
Check the soil for moisture loss, spritzing only when the surface feels dry.
4. Transplant Seedlings Into Pots Once They Measure 3-4 Inches
The seeds should germinate in 7-10 days, sending up a small set of leaves. Remove the plastic humidity cover. Once the seedlings measure 3-4 inches tall, they’re ready for larger pots.
Fill clean 4-inch pots (or use the convenient Jiffy peat pots) 1/3 of the way with the same rich potting mix.
Next, gently loosen each seedling from the tray by pushing the bottom of the cell. Place one seedling in the center of each pot – lightly pat the soil down and water until moist.
5. Harden Off Seedlings & Prepare Fertile Soil Bed
Place the pots outdoors for 1-2 hours a day to ready them for cooler temperatures. Do this for 3-4 days and increase the outdoor time each day.
While hardening off, prepare a well-draining soil bed in a full sun location, tilling a 2-3 inch layer of compost into the soil using a rake.
Dig holes twice the width of each seedling and equal height, spacing holes at least 3 feet apart.
6. Transplant Once 6-12 Inches Tall/1-2 Weeks After Last Frost
Once the tomato plants measure 6-12 inches tall – and ensuring it is 1-2 weeks after your last expected frost date – plant them in the prepared holes with the bottom 2/3 of the stem buried underground to encourage stronger roots.
Backfill with soil and tamp down before watering each plant well. If planting in consistent summer heat with no natural shade, provide a protective shade cloth.
Use a stake/cage to support their development and water daily to maintain moist (not dry/soggy) soil.
4 Tips for Growing San Marzano Tomatoes From Seed
- Once seedlings are in pots, feed them a balanced 10-10-10 NPK fertilizer every week – this helps encourage foliage growth, not fruit (a different fertilizer will be used later to promote fruit production).
- For urban gardens or ones with poor sunlight levels, it may be wiser to transplant your tomato seedlings permanently into 20-gallon containers to provide more control over lighting conditions – especially if a low yield is unimportant. Pest infestations are far less likely this way too.
- For first-time tomato growers, it can be much simpler to achieve seed germination by using a propagator (find it here) – this provides a humidity dome, cell tray, and heated base all in one!
- Record your progress for future reference – note down things like germination rates, specific soil used, temperatures, watering regimen, etc.
Growing & Caring for San Marzano Tomatoes
Now that you have the steps to take your San Marzano tomatoes from seed to plant, it’s time to encourage amazing results.
Provide the right growing conditions and some TLC to take them from decent to delicious!
Ideal Soil
In nature, San Marzano tomatoes grow in fertile, volcanic soil in the fields of Naples, so replicate this with nutrient-rich soil that incorporates compost or well-rotted manure.
(Adding nitrogen-boosting coffee grounds is also recommended!)
Also, this variety prefers slightly acidic soil pH (6.0-6.8) so use a soil tester before planting, and alter levels accordingly.
Lighting Requirements
Choose an area that gets between 6 and 8 hours of sun per day, but ensure the tomatoes won’t be baking in direct sunlight the entire time – a shade cover, like this one, can help with this.
Watering & Fertilizing
Prevent overwatering at all costs by using a sprinkler or drip irrigation – this ensures even water distribution on hot days and gives you greater control. Water only when the soil feels dry.
Before transplanting your seedlings to the garden, apply a slow-release fertilizer (Tomato Tone is excellent) into the planting hole and continue to apply every other week up until ripening.
Harvesting
Harvest once the fruit is plump and firm. You can either pick when the fruit is deep red or still slightly green/yellow as it will continue to ripen.
Hold the tomato and carefully twist to free it from the connecting stem or use pruning shears on tough stems.
Store tomatoes in a paper bag for immediate use or in your refrigerator crisper for several days.
San Marzano Tomato Common Questions:
Do San Marzano Tomatoes Have Seeds?
San Marzano tomatoes contain seeds, but they have fewer seed cavities than regular tomatoes.
While the average tomato commonly has four seed pockets containing 200-300 seeds, San Marzano varieties have just two seed pockets due to their elongated shape.
Can I Save Seeds From San Marzano Tomatoes?
Yes. Choose the largest ripe tomato and wash it to prevent soil-borne bacteria from contaminating the seeds.
Slice into quarters and depending on your chosen seed-saving method, you can either pick the seeds directly out using tweezers or squeeze the fruit pulp into a mason jar to ferment the seeds first.
How Long Does It Take for San Marzano Seeds To Germinate?
San Marzano tomato seeds should germinate in 7-10 days when grown in ideal conditions.
This includes a consistent temperature range of 70-80°F, maintaining humidity with a plastic cover or propagator, providing consistent sunlight, and maintaining moist soil.
How Tall Do San Marzano Tomato Plants Get?
San Marzano tomato plants typically reach 5-6 feet, especially during longer periods of warm weather, which is why it’s essential to provide support cages or trellises.
Height varies among hybridized San Marzano varieties with the dwarf cultivar ‘Nano’ reaching under 3 feet at maturity.
Quantities: 250mg, 1oz, 4oz, 1lb, 5lb packs.
Offering both organic and open-pollinated seeds. Seed quantities vary.
Quantities: Sampler (~15 seeds) and Large (~80 seeds). Indeterminate.