How to Grow Grand Bleu
Grand Bleu
Solanum lycopersicum 'Grand Bleu'
vegetableGrand Bleu is a French heirloom tomato variety known for its distinctive dark blue-purple coloring on the shoulders and upper portions of the fruit. The tomatoes are medium to large, typically weighing 4-8 oz, with a complex, rich flavor that combines sweetness with subtle earthy notes. This indeterminate variety is prized by gardeners for its striking appearance and gourmet taste.
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Example Grand Bleu timeline · Pittsburgh, PA (Zone 6b)
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Plant Grand Bleu
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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Harvest Grand Bleu
Around Jul 1≈ 75 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Grand Bleu dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 5-9; can be grown in zones 3-4 with season extension
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Seedling
3-4 weeksTiny plants with 2-4 true leaves, tender green growth
Maintain consistent moisture and warmth (70-75°F). Provide bright light 14-16 hours daily under grow lights. Begin fertilizing with dilute liquid fertilizer once true leaves appear.
Vegetative
3-4 weeks after transplantingStrong growth with multiple branches, deep green foliage, no flowers yet
Harden off transplants gradually before planting outdoors. Plant deeply, removing lower leaves. Install sturdy stakes or cages early. Pinch off lower leaves as plant grows (6 inches from ground) for air circulation.
Flowering
2-3 weeksFirst flower clusters appear, small yellow flowers develop on the main stem and branches
Maintain consistent watering and temperature (65-80°F). Ensure adequate pollinator activity. Continue removing lower foliage. Apply balanced fertilizer every 2-3 weeks. Prune suckers on indeterminate varieties to direct energy to fruit production.
Fruiting
4-6 weeks until color change beginsGreen fruits develop and swell; distinctive blue-purple coloring begins appearing on shoulders as fruit matures
Maintain steady water supply to prevent blossom end rot and fruit cracking. Provide shade cloth in extreme heat (above 90°F) to preserve color and flavor. Continue pruning lower leaves for airflow. Side-dress with compost or fertilizer every 3 weeks.
Ripening & Harvest
2-3 weeks per flush; continues until frostFruits develop full dark blue-purple shoulders with red coloring on the lower portions; rich, complex aromas develop
Reduce watering slightly to concentrate flavors, but don't let plant stress severely. Pick tomatoes at first blush of color change (break stage) for best flavor development off the vine. Handle carefully to avoid bruising prized fruits.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Hand-pick early in morning or evening; encourage parasitic wasps; use Bt (Bacillus thuringiensis) if severe
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Use reflective mulches; spray neem oil or insecticidal soap; maintain strong air circulation
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Increase humidity; spray water on undersides of leaves; use neem oil or sulfur dust if needed
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Remove affected leaves immediately; mulch to prevent soil splash; improve air circulation; apply copper fungicide preventatively
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Remove infected tissue; ensure excellent air circulation; apply chlorothalonil or copper fungicide; avoid overhead watering
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Remove lower infected leaves; apply copper or sulfur fungicide; water at base only
Uses
Gourmet slicing and fresh cooking
CulinaryGrand Bleu's rich, complex flavor with sweet and earthy undertones makes it exceptional for fresh slicing, salads, and cooking. The striking blue-purple color adds visual appeal to any dish. [source]
Sauce and preservation
CulinaryThe high sugar content and rich taste make Grand Bleu excellent for fresh tomato sauce, pasta sauce, and canning. The color may fade somewhat during cooking but the flavor remains exceptional. [source]
Antioxidant-rich food
MedicinalLike all dark-colored tomatoes, Grand Bleu is rich in lycopene and anthocyanins, powerful antioxidants associated with reduced heart disease risk and cancer prevention. [source]
Ornamental and decorative
CraftThe striking deep blue-purple coloring makes Grand Bleu attractive for decorative purposes, food photography, and garden display. The unusual color draws attention and makes excellent conversation pieces. [source]
Pollinator garden support
WildlifeTomato flowers attract native bees and beneficial insects. Growing Grand Bleu contributes to supporting pollinators and beneficial garden ecosystems. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Grand Bleu tomatoes develop their signature blue-purple color starting at the shoulder and gradually spreading downward. Harvest at the 'break stage' (first blush of color change) for the best flavor development, as they will ripen fully off the vine over 2-3 days at room temperature. For peak flavor, allow some fruits to fully ripen on the plant in mild weather. This is an indeterminate variety that produces until frost, so harvest regularly to encourage continued production.
Fun Facts
- 🌱 Grand Bleu's striking blue-purple color comes from anthocyanins (the same pigments in blueberries), making it one of the few naturally occurring dark-colored tomato varieties. This coloring is fully developed and stable, not a result of disease or unripeness.
- 🌱 This French heirloom variety has been grown and preserved by gardeners for generations, representing part of France's rich tomato heritage. It's sometimes called 'Bleu de Sologne' or similar regional names across different French growing regions.
- 🌱 The blue coloring is most intense when plants experience cool nights and sunny days, and it actually becomes MORE pronounced when the plant experiences mild stress—making cool-season growing conditions ideal for color development.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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