How to Grow Alert Tomato
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Alert Tomato
Solanum lycopersicum 'Alert'
vegetableAlert is a compact, determinate tomato variety bred for early maturity and cold tolerance, making it ideal for short-season growing regions. It produces small to medium-sized red fruits with excellent flavor and disease resistance. This variety is particularly valued by gardeners in northern climates who need reliable production despite cool weather.
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Example Alert Tomato timeline · Pittsburgh, PA (Zone 6b)
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Plant Alert Tomato
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 Alert Tomato
Around Jun 6≈ 50 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Alert Tomato dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Zones 3-8; thrives in cool to moderate climates with short growing seasons
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Seedling
3-4 weeksTiny sprouts with cotyledons (seed leaves) emerge in 5-10 days; first true leaves appear within 2 weeks
Keep soil moist but not waterlogged. Provide bright light (grow lights 2-3 inches above seedlings for 14-16 hours daily). Maintain 70-75°F. Thin seedlings or transplant to individual containers at true leaf stage.
Vegetative Growth
3-4 weeks after transplantingRobust stem development with multiple sets of leaves; plant grows stockier and bushier. Alert typically remains more compact than indeterminate varieties.
Harden off seedlings by gradually exposing to outdoor conditions over 7-10 days. Transplant after last frost when soil is 60°F+. Keep soil consistently moist. Support plants with stakes or cages early. Prune lower leaves once flowering begins to improve air circulation.
Flowering
2-3 weeksYellow flowers appear in clusters; plant reaches its mature height and width. Alert's early flowering is a key trait.
Maintain consistent watering (critical during flowering to prevent blossom end rot). Apply 2-3 inches of mulch around base. Side-dress with balanced fertilizer or compost. Ensure adequate calcium availability. Pollinate flowers by gently shaking stems on warm days.
Fruiting
3-4 weeksSmall green fruits appear and gradually enlarge to 2-3 inches diameter. Fruits transition from green to red as they ripen.
Continue consistent watering—critical during fruit development. Reduce nitrogen to avoid excess foliage at expense of fruit. Apply mulch to regulate soil temperature and moisture. Continue pruning lower foliage. Watch for pests and diseases.
Harvest
2-4 weeks of peak harvestFruits reach full red color and yield to gentle pressure. Alert often produces concentrated crop over 2-3 week period due to determinate growth.
Harvest fruits when fully red for best flavor, or pick at 'breaker stage' (first blush of color) if early fall frost threatens. Continue picking to encourage new fruit set. Water consistently throughout harvest.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Hand-pick large caterpillars daily. Encourage parasitic wasps. Use Bt (Bacillus thuringiensis) spray if infestation is severe. Monitor regularly.
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Spray with strong water stream to dislodge. Use insecticidal soap or neem oil. Encourage beneficial insects like ladybugs.
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Increase humidity with regular misting. Spray with water or insecticidal soap. Use sulfur dust in hot weather. Neem oil is effective.
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Use yellow sticky traps. Spray with insecticidal soap or neem oil weekly if needed. Remove heavily infested leaves.
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Prune lower leaves to improve air circulation. Remove infected leaves immediately. Apply copper fungicide or sulfur. Mulch to prevent spore splash. Ensure adequate spacing.
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Improve air circulation through pruning and spacing. Apply fungicides (copper, sulfur, or chlorothalonil) preventatively in wet weather. Remove infected leaves and destroy. Alert has some resistance.
Uses
Fresh eating and sauces
CulinaryAlert's early maturity and reliable production make it perfect for fresh eating, salads, and cooking. The compact plant is ideal for containers and small gardens, while the concentrated harvest makes it excellent for sauce, paste, and canning projects. [source]
Canning and preservation
CulinaryAlert's concentrated harvest window and medium-sized fruits are ideal for home canning, freezing, and preserving. The meaty texture and good acidity make excellent sauce and paste. [source]
Cold-hardy gardening
HouseholdAlert's exceptional cold tolerance and early maturity make it invaluable for short-season growers and northern climates where frost arrives early. It thrives where other tomatoes struggle, extending the growing season. [source]
Lycopene and antioxidants
MedicinalLike all red tomatoes, Alert contains high levels of lycopene, a powerful antioxidant associated with reduced cardiovascular disease risk. Red tomatoes are best consumed cooked to maximize lycopene bioavailability. [source]
Beneficial insect support
WildlifeTomato flowers attract pollinators including bees and other beneficial insects. The compact Alert plant in containers or gardens provides valuable forage during mid to late summer. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Alert fruits are ready to harvest when fully red and slightly soft to gentle pressure, typically 50-65 days after transplanting. This determinate variety concentrates its harvest into a 2-3 week window, making it excellent for preserving/canning. Harvest in early morning when fruits are coolest. Gently twist and pull, or cut with pruners to avoid damaging vines. Fruits picked at breaker stage (first color) will ripen indoors if early frost threatens. Continue harvesting regularly to encourage new fruit set.
Fun Facts
- 🌱 Alert was bred in Canada specifically for cold-season growing and is named for its 'alert' to early maturing in short seasons. It remains one of the most cold-tolerant tomato varieties available.
- 🌱 As a determinate (or 'bush') variety, Alert produces most of its fruit over a concentrated 2-3 week period, unlike indeterminate varieties that produce continuously. This makes it perfect for gardeners who want to preserve or can large batches all at once.
- 🌱 Alert tomatoes are excellent for container growing—a single plant in a 5-gallon pot can produce 30-50 pounds of fruit over the season, making it ideal for patio and balcony gardens where space is limited.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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