San Marzano tomato
Solanum lycopersicum 'San Marzano'. Family Solanaceae. Annual.
Also called San Marzano plum tomato, San Marzano paste tomato.
San Marzano is a vigorous, usually indeterminate tomato grown as an annual for its elongated red fruit, thick flesh and relatively few seeds. Gardeners grow it chiefly for sauces, paste and preserving; it needs sturdy support and a long, warm growing season, with greenhouse protection often helpful in cooler regions.
At a glance
- Sun
- Full sun, ideally at least 6-8 hours daily; a warm, sheltered position improves ripening.
- Water
- Water deeply and regularly, keeping the root zone evenly moist but not waterlogged. Containers may need daily watering in hot weather.
- Soil
- Fertile, well-drained soil enriched with compost; ideally pH 6.0-6.8. Use fresh, good-quality vegetable potting mix in containers.
- Height
- 6-8 ft (1.8-2.4 m)
- Spread
- 2-3 ft (0.6-0.9 m)
- Flowers
- Small yellow flowers from late spring through summer, continuing into autumn while conditions remain warm.
- Foliage
- Green, divided, softly hairy leaves with a strong tomato scent when handled.
- Growth
- Fast in warm weather
- Care needed
- High
The year at a glance
- Pollinators
- Low allergen
- Edible
| J | F | M | A | M | J | J | A | S | O | N | D | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Flowers | ||||||||||||
| Fruit | ||||||||||||
| Plant |
Northern hemisphere months. In Australia, shift them by six.
- Difficulty
- Hard
- Toughness
- Needs looking after
Will it suit your garden?
Pick your zone, country, light and whether you have pets.
Full sun is 6 or more hours of direct sun a day, part shade 3 to 6 hours, shade under 3.
How it grows
Planting day
0.8 ft (0.25 m)
After 1 year
7 ft (2.1 m)
full size
Full size in one season.
From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.
Good to know
- Cats and dogs
- Toxic
- Growth rate
- Fast
Care
Jobs through the year
- WaterMay–Jun, every 3 days
- Check established ground plants and water deeply as needed; new transplants need closer attention.
- WaterJul–Aug, every 2 days
- Water at soil level as needed to maintain even moisture, allowing for rain.
- WaterSep–Oct, every 4 days
- Maintain even root-zone moisture while plants are cropping; reduce watering in cool, wet weather.
- ProtectMay–Jun
- Harden off before planting after frost; install sturdy supports and tie stems as they grow.
- MulchJun
- Mulch once soil is warm, keeping material clear of stems.
- FeedJun–Sep, every 14 days
- Apply tomato feed from first fruit set, adjusting frequency to the label.
- PruneJun–Sep, every 7 days
- For indeterminate plants, remove unwanted sideshoots and yellow lower leaves; do not routinely sideshoot determinate strains.
- PruneAug–Sep
- Pinch out indeterminate growing tips about four weeks before cropping is expected to end.
- HarvestAug–Oct
- Pick fully red fruit regularly and bring mature remaining fruit indoors before frost.
- Plant out after frost danger has passed, once nights are consistently above 50°F (10°C) and the soil has warmed.
- Install a tall stake, strong cage or trellis at planting, and tie new growth loosely as it develops.
- Water at soil level and mulch after the soil warms to reduce moisture fluctuations and soil splash.
- Feed with a tomato fertiliser according to its label once fruit begins setting; avoid excessive nitrogen.
- For container growing, use one plant per pot holding at least 10 US gal (38 L), with unobstructed drainage.
- Ventilate greenhouses well and gently tap flower trusses to help release pollen.
Pruning. For an indeterminate strain, train one or two main stems and pinch out unwanted side shoots while small; remove lower leaves as they yellow or touch the soil. About four weeks before your expected end of the growing season, pinch out the growing tips to favour existing fruit; do not routinely remove side shoots from a determinate strain.
Harvest
Pick elongated fruits when they are fully red and slightly yielding, clipping or gently twisting them from the truss. The first ripe fruit commonly arrives about 75-90 days after transplanting in warm conditions, but takes longer in cool summers; harvest regularly and bring mature fruit indoors before frost.
Through the year
- Late winter
- Sow indoors about 6-8 weeks before your expected last frost, using warmth and strong light.
- Spring
- Pot seedlings on as roots fill their containers; harden them off gradually before outdoor planting.
- Late spring
- Plant out once frost risk has passed and nights are warm; install supports and water thoroughly.
- Early summer
- Mulch warm soil, tie in stems and begin regular feeding when fruit starts setting.
- Summer
- Maintain even moisture, manage side shoots on indeterminate plants and check for pests and disease.
- Late summer
- Harvest fully coloured fruit regularly and stop growing tips if the remaining warm season is short.
- Autumn
- Gather remaining mature fruit before frost, remove spent plants and clean supports.
In the garden
- Train along a sturdy trellis at the back of a sunny vegetable bed for vertical structure.
- Grow with basil and parsley in a kitchen garden for convenient sauce ingredients.
- Use large containers against a sunny courtyard wall, allowing room for airflow and access.
- Repeat supported plants through a potager to give productive beds height and rhythm.
Garden styles it suits: Potager (kitchen garden), Edible landscape, Homestead, Cottage garden, Mediterranean and Small-space.
Plant it with: Basil, Parsley, Chives, Lettuce, French marigold and Sweet alyssum.
Wildlife: Flowers provide pollen for bumblebees and other bees capable of buzz pollination. Birds and small mammals may eat ripe fruit; use wildlife-safe, taut netting if protection is needed.
Problems to watch for
- Blossom-end rot: dark, sunken patches develop at the blossom end of fruit, often after uneven watering. Keep moisture steady, mulch and avoid excessive feeding; add calcium only if a soil test shows a deficiency.
- Tomato blights: spreading leaf spots, dark lesions or rapidly collapsing foliage need prompt attention. Keep leaves dry, improve airflow, remove infected material and use locally approved controls where appropriate; remove badly affected plants.
- Aphids and whiteflies: inspect leaf undersides and tender shoots. Dislodge small colonies with water, encourage natural predators and use a labelled insecticidal soap if needed.
- Poor fruit set: cold nights, extreme heat or humid, still greenhouse air can prevent pollination. Ventilate, maintain steady watering and gently tap flowering trusses; fruit set usually improves when temperatures moderate.
Safety
Ripe fruit is not considered toxic to people, cats, dogs or horses. Leaves, stems and unripe green fruit contain glycoalkaloids and can cause poisoning if eaten in sufficient amounts, especially the foliage; signs include digestive upset, weakness and, in serious cases, neurological or heart effects. Keep pets and horses from eating the plants, and seek medical or veterinary advice after significant ingestion.
Easily confused with
Roma tomato (Solanum lycopersicum 'Roma')
Roma usually has shorter, more oval fruit and a determinate, bushier habit; typical San Marzano has longer, narrower fruit and keeps extending its stems.
The name
San Marzano takes its name from San Marzano sul Sarno, a town in Campania, southern Italy, associated with this type of plum tomato.
Propagation. Sow seed indoors at about 70-80°F (21-27°C). Open-pollinated San Marzano strains generally come true from seed if cross-pollination is avoided; named hybrid strains do not reliably do so. Healthy side shoots can also be rooted as cuttings during the growing season.
Checked against open data
- Accepted botanical name
- Solanum lycopersicum
- In the US and Canada
- Introduced in Alaska, Hawaii, the lower 48 states, Pacific Basin, Puerto Rico and US Virgin Islands.
- Native range
- Peru.
- Measured
- Soil pH 7 to 7.5. Average height 19 cm.
Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.
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