How to Grow Princeton

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Princeton

Solanum lycopersicum 'Princeton'

vegetable

Princeton is a classic determinate (bush-type) tomato variety known for its reliable production of medium-sized, red, flavorful fruits. Developed at Princeton University in the 1950s, it became a popular choice for home gardeners and commercial growers due to its disease resistance and consistent yields. The plant is compact and well-suited to containers, small spaces, and regions with shorter growing seasons.

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Example Princeton timeline · Pittsburgh, PA (Zone 6b)

Plant Princeton
Around Apr 17

Near Pittsburgh's average last spring frost.
Tend & protect
Late spring–summer

Watering, feeding, and pest-watch reminders.
Harvest Princeton
Around Jun 26

≈ 70 days after planting

Sample dates for Pittsburgh, PA. Sign up to get exact Princeton dates for your own zip code.

Growing Conditions

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Sun: Full sun, 6-8 hours daily (8+ hours ideal for fruit production)

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Water: Consistent moisture of 1-1.5 inches per week; water deeply at soil level in early morning. Avoid wetting foliage to reduce disease. Increase watering during fruiting and hot weather. Mulch to retain soil moisture.

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Spacing: 24 inches

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Days to maturity: 70-80 days from transplant

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Planting depth: Start seeds 0.25 inches deep indoors 6-8 weeks before last frost; transplant when 6-8 inches tall and have 2-3 true leaves. Bury stems deeper (up to first true leaves) to encourage stronger root systems.

Soil

Type: Well-draining loamy soil rich in organic matter

pH: 6.0-6.8

Amendments:

Aged compost or well-rotted manure (2-3 inches worked in) Calcium sources (crushed eggshells or gypsum) to prevent blossom end rot Balanced slow-release fertilizer or organic vegetable fertilizer Perlite or coarse sand (if soil is heavy clay)

Growing Zones

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Thrives in zones 5-9; can be grown in zones 3-10 with season extension techniques

3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a 9b 10a

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Growth Stages

Seedling

2-3 weeks

Tiny plants with cotyledons (seed leaves) and emerging true leaves; very delicate

Keep soil moist but not waterlogged. Provide bright light 14-16 hours daily under grow lights. Keep temperature 70-75°F. Thin to strongest seedling if multiple sprout in one cell.

Vegetative Growth

3-4 weeks after transplanting

Bushy plant developing multiple branches, true leaves 2-4 inches long; stems thickening. Plant reaches 12-18 inches tall

Harden off gradually (7-10 days) before transplanting outdoors. Space 24 inches apart. Support with stakes or cages early. Pinch off lower leaves once plant is established to improve air circulation.

Flowering

2-3 weeks

Yellow flowers appear in clusters (typically 5-8 flowers per cluster); plant is full and bushy

Maintain consistent watering; fluctuating moisture can cause flower drop. Avoid excessive nitrogen fertilizer. Ensure adequate sun and air circulation. Can lightly tap flowers midday to aid pollination.

Fruiting

3-4 weeks

Small green fruits develop and enlarge; plant may slow vegetative growth. Fruits gradually mature to bright red

Reduce nitrogen; provide balanced or phosphorus-richer fertilizer (every 2-3 weeks). Water consistently. Prune excess foliage only if fruits are shaded. Monitor for pests and diseases.

Harvest

4-6 weeks (ongoing)

Fruits reach full size (2-3 inches diameter) and are bright red, firm, and fragrant when ripe

Harvest when fully red or allow to ripen on vine for best flavor. Continue harvesting to promote more fruit set. Remove plant once frost threatens; green fruits can ripen indoors at 68-72°F.

Companion Planting

Plan your garden →

Plant with:

Basil Parsley Carrot Onion Marigold Borage Nasturtium Garlic

Avoid planting near:

Brassicas (cabbage, broccoli, cauliflower) Fennel Kohlrabi Other nightshades (pepper, eggplant, potato) - if disease history exists

Common Pests

Hand-pick daily; encourage parasitic wasps; use Bacillus thuringiensis (Bt) spray if infestation is heavy
Spray neem oil or insecticidal soap weekly; use yellow sticky traps; increase air circulation
Strong water spray to dislodge; spray neem oil or horticultural soap; encourage natural predators like ladybugs
Increase humidity; spray water on underside of leaves; use miticide or neem oil if severe
Remove affected leaves; improve air circulation; avoid wetting foliage; apply copper fungicide or sulfur dust
Remove infected leaves immediately; spray with copper or chlorothalonil fungicide; ensure good drainage and airflow

Uses

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Fresh eating and salads

Culinary

Princeton tomatoes have firm flesh, balanced sweetness, and pleasant acidity, making them ideal for fresh consumption in salads, slicing, or eating out of hand. Their medium size and uniform ripening make them perfect for everyday kitchen use. [source]

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Canning and preserves

Culinary

The solid flesh and good flavor make Princeton suitable for canning whole, crushed, or as sauce. Their determinate ripening habit means you harvest a concentrated crop ideal for preservation projects. [source]

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Antioxidant nutrition

Medicinal

Tomatoes are rich in lycopene, a powerful antioxidant linked to reduced risk of certain diseases. Princeton tomatoes, especially when fully ripe and red, provide high levels of this beneficial compound. [source]

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Cooking and sauces

Culinary

The balanced flavor profile and firm texture make Princeton tomatoes excellent for cooked sauces, soups, stews, and pasta dishes. The concentrated harvest period is ideal for making large batches. [source]

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Plant breeding and seed saving

Household

Princeton is an heirloom variety with historical significance in tomato breeding. Home gardeners can save seeds from ripe fruits for next season's planting, preserving this classic cultivar. [source]

This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.

Harvest Tips

Harvest when fruits are fully red, firm, and fragrant—typically 70-80 days after transplanting. Twist and gently pull ripe fruits off the vine. For best flavor, pick in morning after dew dries. You can also pick mature green fruits and ripen indoors at 68-72°F on a windowsill or in a paper bag. A single determinate plant typically yields 15-25 pounds of fruit over the season.

Fun Facts

🌱 Princeton tomatoes were developed at Princeton University in the 1950s and became one of the first widely grown disease-resistant tomato varieties, helping revolutionize home tomato growing.
🌱 As a determinate variety, Princeton grows to a fixed height (usually 3-4 feet) and sets most of its fruit within a narrow window, making it ideal for gardeners who want to harvest and can all their tomatoes at once rather than continuously throughout the season.
🌱 The variety name 'Princeton' reflects its academic origins, and it remains popular among university agricultural extension programs and home gardeners more than 70 years after its introduction.

Gardening Terms

New to gardening? Learn about terms used in this guide:

Full Sun Mulch pH Pollination Transplant True Leaves

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