Why Are My Tomatoes Deformed? Causes, Fixes & Prevention
You've been watering, weeding, and waiting all season — and now your tomatoes look like they came from another planet. Lumpy, cracked, twisted, or hollow: deformed tomatoes are one of the most common complaints from home gardeners. The good news? Most deformities are completely preventable once you know what's causing them.
In this guide, we'll walk through every major cause of tomato deformity, how to identify it, and exactly what to do about it — plus the best tomato varieties to start from seed for a beautiful, productive harvest.
1. Catfacing: The Most Common Tomato Deformity
Catfacing causes deep scarring, puckering, and irregular lobes at the blossom end of the tomato. It looks alarming but the fruit is still edible. The primary cause is cold temperatures during flowering — specifically when nighttime temps drop below 55°F (13°C) while the blossoms are forming. Large-fruited heirloom and beefsteak varieties are most susceptible.
Fix it: Don't transplant tomatoes outdoors until nighttime temps are consistently above 55°F. Use row covers or frost cloth if a cold snap hits during early flowering.
If you love big, bold beefsteak tomatoes, our Mr. Stripey Heirloom Beefsteak Tomato Seeds are a gorgeous heirloom variety — just be sure to plant after your last frost date to avoid catfacing.
2. Puffiness and Hollow Tomatoes
Cut open a tomato and find mostly air? That's puffiness — a condition where the fruit wall develops normally but the seed cavities inside are hollow or underdeveloped. The cause is poor pollination, often from extreme heat (above 90°F/32°C), high humidity, or lack of pollinators during bloom.
Fix it: Gently shake your tomato plants daily to help distribute pollen. Plant pollinator-attracting flowers nearby. Choose heat-tolerant varieties for hot climates.
Our Firebird F1 Hybrid Tomato Seeds are specifically bred to be both cold-hardy and heat-tolerant — an excellent choice for gardeners dealing with temperature extremes.
3. Zippering and Russeting
Zippering appears as a thin brown scar or "zipper" running from the stem to the blossom end. Russeting looks like rough, corky skin patches. Both are caused by cool, wet conditions during fruit set combined with rapid temperature swings. They're cosmetic issues only — the tomato inside is perfectly fine.
Fix it: Improve air circulation around plants, avoid overhead watering, and mulch heavily to stabilize soil temperature.
For a reliable, productive cherry tomato that resists many environmental stressors, try our Lemonsugar Cherry Tomato Seeds — a sweet, prolific variety that handles variable conditions well.
4. Blossom Drop and Misshapen Fruit from Pollination Failure
When tomato blossoms drop before setting fruit — or set fruit that's small and misshapen — the culprit is almost always temperature stress during pollination. Tomatoes need daytime temps between 65–85°F and nighttime temps above 55°F for proper pollen viability. Outside that range, pollen becomes sterile or sticky and won't transfer properly.
Fix it: Use shade cloth during heat waves. Plant in a location with good morning sun and afternoon shade in hot climates. Choose varieties bred for wide temperature tolerance.
The Wonderstar Red Hybrid Tomato is a dependable performer with excellent fruit set even under variable conditions.
5. Herbicide Drift Damage
One of the most dramatic causes of tomato deformity is herbicide drift — particularly from broadleaf herbicides like 2,4-D or dicamba drifting from neighboring properties or lawns. Symptoms include twisted, cupped, or fern-like leaves and severely distorted fruit. New growth will look curled and abnormal.
Fix it: Unfortunately there's no cure once a plant is exposed. Remove severely affected plants. For future seasons, use physical barriers (fencing, hedges) and communicate with neighbors about herbicide use near your garden.
6. Nutrient Imbalances
Calcium deficiency causes blossom end rot — a dark, sunken patch at the bottom of the fruit. Boron deficiency causes internal browning and corky tissue. Excess nitrogen produces lush foliage but poor fruit set and misshapen tomatoes. Soil testing is the most reliable diagnostic tool for nutrient issues.
Fix it: Amend soil based on a soil test. For calcium, ensure consistent watering (irregular watering blocks calcium uptake even when it's present in the soil). Avoid over-fertilizing with high-nitrogen fertilizers once plants are flowering.
Starting with the right variety matters too. Our Tomato Palpatation Oxheart Seeds produce large, meaty, low-seed fruits that are naturally less prone to hollow centers and nutrient-related deformities.
7. Viral Diseases
Tomato mosaic virus, cucumber mosaic virus, and tomato spotted wilt virus all cause distorted, mottled, or stunted fruit. Symptoms include mottled yellow-green leaves, stunted growth, and fruit with uneven ripening or ring spots. Viruses are spread by aphids, thrips, and infected tools.
Fix it: Remove and destroy infected plants immediately. Control aphid and thrip populations. Sanitize tools between plants. Choose virus-resistant varieties (look for V, F, N, T resistance codes on seed packets).
8. Fasciation (Multiple Fused Flowers)
Fasciation causes tomatoes to look like multiple fruits fused together — often producing a large, flat, multi-lobed fruit. It's caused by a mutation in the growing tip, sometimes triggered by cold damage, insect feeding, or random genetic variation. It's harmless and the fruit is edible, though often very large.
Fix it: No fix needed — fasciated tomatoes are edible and sometimes prized for their size. Avoid cold stress during early growth to reduce occurrence.
Shop Our Tomato Seed Collection
Ready to grow a beautiful, productive tomato garden from seed? Browse our full selection of premium tomato seeds — from cherry tomatoes to giant beefsteaks, hybrids to heirlooms.
Related Reading
- From Seed Pack to Harvest Basket: Planning a Productive Vegetable Garden
- Why Are My Seedlings Leggy? Causes, Fixes & How to Prevent It
- Do Marigolds Really Repel Pests? The Science-Backed Answer
Frequently Asked Questions: Deformed Tomatoes
Why are my tomatoes lumpy and misshapen?
Lumpy, misshapen tomatoes are most commonly caused by catfacing (cold temperatures during flowering), fasciation (fused flowers), or poor pollination. Large-fruited varieties like beefsteaks are most prone to these issues. Planting after your last frost date and ensuring good pollinator activity are the best preventive measures.
Are deformed tomatoes safe to eat?
Yes — in almost all cases, deformed tomatoes are perfectly safe to eat. Catfacing, puffiness, zippering, russeting, and fasciation are cosmetic issues only. The exception is if deformity is caused by a viral disease, in which case the fruit may taste off and the plant should be removed to prevent spread.
What causes tomatoes to have a dark sunken bottom?
That's blossom end rot, caused by calcium deficiency — usually due to inconsistent watering rather than a lack of calcium in the soil. Water deeply and consistently, mulch to retain moisture, and avoid high-nitrogen fertilizers that compete with calcium uptake.
Why do my tomatoes look like they have a scar running down the side?
That's called zippering — a thin brown scar from stem to blossom end caused by cool, wet conditions during fruit set. It's purely cosmetic and the tomato is fine to eat.
Can herbicides cause tomato deformities?
Yes. Broadleaf herbicides like 2,4-D and dicamba can drift from neighboring lawns or fields and cause severe leaf curling, twisted growth, and distorted fruit. If you suspect herbicide drift, remove affected plants and use physical barriers in future seasons.
What tomato varieties are least prone to deformities?
Smaller-fruited varieties like cherry and grape tomatoes are generally less prone to catfacing and fasciation. F1 hybrid varieties bred for disease resistance and wide temperature tolerance — like our Firebird F1 Hybrid and Wonderstar Red Hybrid — tend to produce more uniform fruit under variable conditions.
How do I prevent deformed tomatoes next season?
The most impactful steps are: (1) don't transplant until nighttime temps are consistently above 55°F, (2) choose disease-resistant and temperature-tolerant varieties, (3) water consistently to prevent calcium deficiency, (4) encourage pollinators, and (5) test your soil before planting to correct any nutrient imbalances.
Grow More, Grow Better
Whether you're troubleshooting this season's crop or planning next year's garden, starting with premium seeds makes all the difference. Browse our full tomato seed collection and find the perfect variety for your climate and growing style.
🌱 Looking for bulk tomato seeds? Visit our sister site: Trailing Petunia Bulk Seeds — premium seeds in bulk quantities for serious growers.
📖 Growing snapdragons too? Don't miss our bulk site guide: How to Grow Snapdragons from Seed for Cut Flower Production
🎥 Subscribe to us on YouTube for seed starting tutorials, garden tours, and growing tips: @TrailingPetunia on YouTube
Explore Our Complete Gardening Network
Looking for even more flower growing guides, vegetable gardening tips, greenhouse advice, seed-starting tutorials, educational videos, and premium gardening resources? Visit our official Garden Starts Nursery Gardening Network to discover all of our growing guides, videos, social media communities, and gardening platforms in one convenient place.
🌿 Explore Our Complete Gardening Network for Growing Guides, Videos, Seed Starting Tips & More