Growing tomatoes is an ideal option for beginner vegetable gardeners. They’re pretty easy to cultivate and, when you get conditions and care right, you can enjoy a bumper crop. However, poor practices can lead to problems with tomato plants.

There are several possible reasons why your tomatoes have ugly black spots on the bottom. Learning about the causes, whether your fruits are salvageable, and how to prevent the problems going forward will help you yield the most handsome, healthy harvest.

5 Reasons Why Your Tomatoes Have Ugly Black Spots on the Bottom

Being aware of some of the common reasons for tomatoes developing unsightly black patches can help you take steps to prevent inedible fruits.

1. Anthracnose: A common fungal rot that ripe and overripe tomatoes are particularly susceptible to, especially when they’re close to wet ground. The black spots start small, circular, and depressed, growing over time until the entire fruit rots. The spores can spread to other tomato plants.
2. Bacterial spot: The fruit develops small, brown to black spots that can fall away, leaving a hole. This infection can spread, and you shouldn’t eat the fruit as it can host secondary pathogens.
3. Bacterial speck: This infection commonly occurs during persistent cool, wet weather. The raised spots that appear on the fruits are smaller than those caused by bacterial spot—around the size of a pencil tip.
4. Blossom end rot: Irreversible water-soaked lesions caused by calcium deficiency. It doesn’t spread to other tomatoes, so you can just remove the blackened fruit.
5. Early blight: This fungal tomato plant disease causes brown to black, leathery, sunken spots with concentric rings developing on the fruit. If you don’t take prompt action, early blight can result in significant crop loss.

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7 Ways to Prevent Black Spots on Tomatoes

Preventative measures vary depending on the type of tomato plant problem that’s causing the black spots. Below are some cultural best practices and other tips that can help reduce the risk of many diseases or fungal infections from developing.

1. Select the right cultivar: Some tomato varieties are better suited to specific conditions, and others are more resistant to certain diseases.
2. Plant at the right time: Avoid transplanting tomato seedlings too early. If the soil is too cold, it can affect root development and essential calcium uptake.
3. Get it right with spacing and air circulation: Don’t have your tomato plants crowded too close together. Staking and pruning tomato plants can also help. Poor airflow promotes pathogens.
4. Provide the right nutrients: Fertilize heavy-feeding tomatoes regularly, especially when growing in pots. Testing your soil and checking formulas helps, as overfertilizing (especially during early fruiting) and excess nitrogen can promote disease-related black spots. 
5. Minimize stress: Avoid over- or underwatering and water tomato plants at the base rather than overhead to prevent wet leaves. A layer of mulch can help to promote even moisture. Use shade cloths to protect your plants from the scorching summer sun.
6. Keep weeds at bay: Pull unwanted interlopers out of your tomato rows. Weeds can encourage pests, cause airflow issues, and use up nutrients that heavy-feeding tomatoes will appreciate. 
7. Rotate crops: Allowing two to three years in between planting tomatoes (and other species in the nightshade family) in the same location can help prevent pathogens from recurring.

How to Fix or Revive Tomatoes With Black Spots

Once your tomatoes develop black spots, you won’t be able to reverse this problem. However, in some instances, changing watering practices, pruning away problematic fruit and leaves, improving airflow, or treating with a fungicide can help prevent the problem from worsening or spreading. Sometimes, you’ll need to remove all infected plants. 

Don’t leave infected plant material to decompose in the ground or on compost piles, as this can increase the risk of spreading disease.