Tomatoes Turning Black

If you see your tomatoes turning black, it can be a worrying sight. Those dark, sunken spots on the bottom of your fruit are a common problem for gardeners. If your tomato fruits develop dark, sunken spots, you might be dealing with blossom end rot. This is just one of several issues that can cause blackening, and identifying the correct cause is the first step to saving your crop.

This guide will help you diagnose why your tomatoes are black, explain the science behind each problem, and give you clear, actionable steps to fix it and prevent it in the future. Let’s look at the main culprits.

Seeing black areas on your tomatoes is a symptom, not a disease itself. The location, texture, and pattern of the blackening tell you what’s wrong. The main causes fall into two categories: physiological disorders and infectious diseases.

Physiological disorders are caused by environmental stress or nutrient issues within the plant. Infectious diseases are caused by fungi, bacteria, or viruses that attack the plant. Here is a quick overview of the most common reasons.

Common Causes Of Black Spots And Rot

Blossom End Rot: Dark, leathery spots on the blossom end (bottom) of the fruit.
Late Blight: Rapidly spreading dark lesions on leaves, stems, and fruit, often with a white moldy fringe in humid conditions.
Anthracnose: Small, circular, sunken black spots on ripe or ripening fruit.
Bacterial Spot/Canker: Small, dark, scabby spots on fruit, often with yellow halos on leaves.
Sunscald: White or pale yellow patches that turn black and papery, usually on the side facing the sun.
Fusarium or Verticillium Wilt: Overall plant wilting, with dark streaks inside the stems and potential fruit discoloration.

How To Diagnose Your Tomato Problem

Look closely at where the black appears. Is it only on the bottom of the fruit? Is it on the leaves first? Does the plant itself look wilted? Answering these questions will point you to the right solution. The following sections break down each cause in detail.

Blossom End Rot: A Calcium Deficiency Problem

Blossom end rot is perhaps the most frequent cause of tomatoes turning black on the bottom. It starts as a small, water-soaked spot at the blossom end (the opposite end from the stem) that enlarges, turns dark brown or black, and becomes sunken and leathery.

It’s crucial to understand that blossom end rot is usually not due to a lack of calcium in the soil. More often, it’s caused by inconsistent watering that prevents the plant from taking up the calcium that is already present.

Symptoms of Blossom End Rot

Dark, sunken, leathery spot on the blossom end of the fruit.
Usually appears on the earliest, largest fruits.
The spot may start small and expand as the fruit grows.
The rest of the fruit often ripens normally, though the rot can invite secondary infections.

Causes and Immediate Fixes

The primary cause is a calcium deficiency in the developing fruit. This deficiency is typically triggered by:

Irregular Watering: Fluctuations between dry and wet soil disrupt calcium uptake.
Rapid Early Growth: From too much nitrogen fertilizer, which makes the plant grow faster than it can take up calcium.
Damaged Roots: From cultivation, pests, or waterlogged soil, which limit nutrient absorption.
Soil pH: Extremely high or low pH can lock up calcium, making it unavailable.

To fix blossom end rot immediately, follow these steps:

Remove affected fruits to help the plant redirect energy.
Apply a consistent watering schedule. Soil should be moist like a wrung-out sponge, not soggy or dusty dry.
Mulch around plants with straw or wood chips to retain soil moisture.
If a soil test confirms low calcium, add gypsum (calcium sulfate) or crushed eggshells to the soil for long-term improvement. Avoid high-nitrogen fertilizers.

Late Blight: A Serious Fungal Disease

Late blight is a devastating and fast-moving disease caused by the fungus-like organism *Phytophthora infestans*. It’s the same disease that caused the Irish Potato Famine. It can destroy entire plants in just days under cool, wet conditions.

Unlike blossom end rot, late blight affects leaves, stems, and fruit. The black areas on fruit are typically firm and greasy-looking at first, spreading quickly. In humid weather, you might see a white, fuzzy mold growth around the edges of the spots.

Identifying Late Blight

Leaves: Large, irregular, water-soaked gray-green lesions that turn brown and papery. A white mold may appear on the underside in high humidity.
Stems: Dark brown to black lesions.
Fruit: Shiny, dark brown or greasy gray firm spots that rapidly cover the fruit, eventually causing it to rot.

How to Manage Late Blight

Late blight spores travel on the wind and need wet foliage to infect plants. Management requires quick action:

Remove and Destroy: Immediately remove infected plants. Do not compost them; bag and trash them to prevent spore spread.
Apply Fungicides: For organic options, use copper-based fungicides preventatively. Conventional gardeners can use specific fungicides labeled for late blight. Apply before wet weather if the disease is in your area.
Improve Airflow: Space plants properly and use stakes or cages to keep foliage dry.
Water at the Base: Use drip irrigation or soaker hoses to avoid wetting leaves.
Choose Resistant Varieties: Some tomato varieties offer partial resistance to certain strains of late blight.

Anthracnose: A Fruit Rot Fungus

Anthracnose is a common fungal disease caused by *Colletotrichum* species. It primarily affects ripe or overripe fruit, leading to small, circular, sunken black spots. These spots can merge and create large rotten areas, often teeming with salmon-colored spore masses in the center.

This fungus lives in the soil and splashes onto lower fruit during rain or overhead watering. It’s more prevalent in warm, humid weather.

Recognizing Anthracnose Damage

Small, circular, sunken spots on ripe fruit.
Spots darken from tan to brown to black as they enlarge.
In wet conditions, pink or orange spore clusters appear in the center of the spots.
Fruit may rot completely, especially if left on the ground.

Prevention and Control Strategies

Since anthracnose infects from the soil, prevention focuses on barrier methods and sanitation.

Mulch Heavily: Apply a thick layer of straw or plastic mulch to create a barrier between the soil and the fruit.
Stake and Prune: Keep plants staked and prune lower leaves to improve airflow and prevent soil splash.
Water at the Base: Avoid overhead watering.
Harvest Promptly: Pick fruit as soon as it ripens; do not let overripe fruit sit on the plant or ground.
Rotate Crops: Do not plant tomatoes or related crops (peppers, eggplants) in the same spot for at least 2-3 years.
Use Fungicides: As a last resort, apply registered fungicides early in fruit development if you have a history of anthracnose.

Bacterial Spot And Bacterial Canker

These are two separate but similar bacterial diseases that cause black lesions on fruit. They are spread by splashing water, tools, and even on infected seeds or transplants.

Bacterial Spot shows as small, dark, raised or scabby spots on green fruit, sometimes with a water-soaked appearance. Leaves develop small, dark spots with yellow halos. Bacterial Canker is more systemic and severe. Fruit spots are often called “bird’s eye” spots—white halos with dark, raised centers. Leaves wilt and stems may have brown streaks inside.

Managing Bacterial Diseases

Bacterial diseases are difficult to control once established. Focus on prevention and containment:

Buy Certified Disease-Free Seeds and Transplants: This is the most critical step.
Practice Sanitation: Sterilize garden tools with a bleach solution. Wash your hands after handling infected plants.
Remove Infected Plants: Pull and destroy severely infected plants to protect healthy ones.
Copper Sprays: Copper-based bactericides can slow the spread if applied early, but they are not a cure.
Rotate Crops: Avoid planting tomatoes or peppers in the same bed for 2-3 years.
Water at the Base: Minimize leaf wetness.

Sunscald: Environmental Damage

Sunscald is not a disease but physical damage from intense sunlight. It happens when fruit that was previously shaded by leaves becomes suddenly exposed, often after pruning, pest damage, or natural leaf drop. The sun “burns” the skin, causing a white or yellow patch that becomes thin, wrinkled, and turns black as secondary fungi move in.

Preventing Sunscald

Avoid over-pruning, especially during hot, sunny weather. Leave enough foliage to shade the fruit.
Use cages or stakes that allow for natural leaf cover.
If you must prune heavily, do it gradually to allow the plant to adjust.
Choose varieties with good foliage cover.

Fusarium And Verticillium Wilt

These are soil-borne fungal diseases that clog the plant’s vascular system, causing wilting, yellowing, and eventual plant death. While the main symptom is wilting leaves, the stress can lead to poor fruit development and discoloration, including potential blackening. You can confirm these wilts by cutting a lower stem; brown streaks will be visible inside the vascular tissue.

The only effective control is prevention through using resistant varieties. Look for tomato seed packets with “F” (Fusarium resistant) and “V” (Verticillium resistant) codes. Rotate crops and remove infected plant debris from the garden.

Integrated Prevention Plan For Healthy Tomatoes

The best approach to stop tomatoes turning black is a season-long strategy focused on plant health. Here is a step-by-step plan.

Step 1: Start With Healthy Soil and Resistant Varieties

Test your soil every few years to check pH and nutrient levels. Amend soil with compost for structure and nutrients. Always choose disease-resistant tomato varieties suited to your climate. The codes on seed packets (like VFN) are your best defense.

Step 2: Master Watering and Mulching

Consistent moisture is key. Water deeply 1-2 times per week, depending on weather, to encourage deep roots. Use a soaker hose or drip irrigation. Immediately after planting, apply 2-3 inches of organic mulch like straw or shredded leaves. This regulates soil temperature, retains moisture, and prevents soil-borne diseases from splashing up.

Step 3: Ensure Proper Spacing and Support

Crowded plants stay wet and spread disease faster. Space plants according to their mature size, usually 24-36 inches apart. Use sturdy stakes, cages, or trellises to keep plants upright, improve air circulation, and keep fruit off the ground.

Step 4: Practice Smart Fertilization

Over-fertilizing, especially with high-nitrogen formulas, promotes lush leaves but weak fruit and can cause blossom end rot. Use a balanced, slow-release fertilizer or one formulated for tomatoes at planting. Side-dress with compost or a low-nitrogen fertilizer when fruits first set.

Step 5: Implement Crop Rotation and Sanitation

Never plant tomatoes, peppers, potatoes, or eggplants in the same spot two years in a row. Rotate them to a different bed for at least 2-3 years. At the end of the season, remove all plant debris. Clean your tools and stakes with a disinfectant to kill overwintering spores.

When To Harvest And Salvage Affected Fruit

If you catch problems early, you can sometimes salvage part of the fruit. For blossom end rot or anthracnose spots that are small and localized, you can cut away the black portion; the rest of the fruit is often safe to eat. Do not eat fruit with late blight or bacterial canker, as it can be inedible.

For sunscald, cut away the damaged tissue; the rest is fine. Always compost or discard any severely rotted or diseased fruit away from your garden area.

Frequently Asked Questions (FAQ)

Why Are My Tomatoes Black on the Bottom?

This is almost always blossom end rot, a disorder caused by calcium deficiency in the fruit due to irregular watering. Check your watering habits and soil moisture consistency first.

Can You Eat Tomatoes That Have Turned Black?

It depends on the cause. You can cut away small areas affected by blossom end rot or sunscald and eat the rest. Do not eat fruit rotted by late blight, anthracnose, or bacterial diseases, as it may taste bad or harbor harmful organisms.

How Do You Treat Black Spots on Tomato Leaves?

Black spots on leaves are usually a sign of fungal or bacterial disease like early blight, Septoria leaf spot, or bacterial spot. Remove affected leaves, improve air circulation, avoid wetting foliage, and apply appropriate organic or conventional fungicides as a preventative measure.

What is the Best Way to Water Tomatoes to Prevent Problems?

Water deeply and consistently at the base of the plant using a soaker hose or drip irrigation. Aim for 1-1.5 inches of water per week, adjusting for rain. Mulch heavily to maintain even soil moisture, which is critical for preventing blossom end rot and reducing soil splash.

Are Black Tomatoes a Different Variety?

Yes, there are many heirloom and hybrid tomato varieties that are naturally dark purple, brown, or “black” when ripe, such as ‘Black Krim’ or ‘Cherokee Purple’. These are perfectly healthy. The problem is when normally red or green fruit develops localized black spots, rot, or lesions, which indicates a disorder or disease.