Why Are My Green Tomatoes Rotting on the Vine?

Summer’s bounty brings juicy red tomatoes to backyard gardens across the country. After months of tending your plants, it’s exciting to watch the tomatoes ripen from green to brilliant red. But sometimes, gardeners notice their green tomatoes rotting on the vine before they have a chance to ripen. Seeing your hard work go to waste is always disappointing.

In this article, we’ll explore the common causes of green tomatoes rotting on the vine and give you tips to prevent it from happening in your garden.

Common Causes of Green Tomatoes Rotting on the Vine

Several issues can cause green tomatoes to rot before they ripen. Here are some of the most common culprits:

Blossom End Rot

Blossom end rot is one of the leading causes of tomatoes rotting on the vine while still green. It first appears as a sunken, brownish-black spot at the bottom of the tomato. As the condition worsens, the spot spreads, and the tomato shrivels and rots.

Blossom end rot is caused by a calcium deficiency in the plant, often brought on by inconsistent watering. Calcium is only available to plants through the water in the soil. Irregular watering can cause calcium to precipitate out and become unavailable to the plant. Hot, dry weather also exacerbates the issue by accelerating moisture evaporation from the soil.

Factors that contribute to blossom end rot include:

• Dramatic shifts in soil moisture from very wet to very dry conditions
• Allowing the soil to completely dry out between waterings
• Heavy rainfall after a prolonged dry spell
• Very high temperatures over 90°F which stress plants
• Compacted or heavy clay soils that retain too much or too little moisture

To avoid blossom end rot, aim to keep soil moisture steady. Water tomato plants 1-2 inches per week, and increase frequency during hot and dry spells. Using drip irrigation or soaker hoses can help maintain optimal moisture at the roots.

Early Blight

Early blight is a fungal disease that can also cause green tomatoes to rot. It produces dark spots on tomato leaves, stems, and fruit. These spots often have distinctive concentric rings, giving them a “bull’s eye” pattern.

Wet foliage encourages the development and spread of early blight. The fungus that causes early blight (Alternaria solani) thrives in cool, humid conditions. Overhead watering late in the day allows the spores access to leaves and fruit overnight when moisture lingers.

Signs of early blight infection include:

• Brown target-like lesions on leaves first appear on the lower, older leaves
• Dark-colored spots on stems that girdle the stem
• Leaves that yellow, wither and drop
• Fruit spots that are dark, sunken, and enlarged, eventually rotting the tomato

To prevent early blight, avoid wetting foliage when watering. Drip irrigation and soaker hoses deliver water right to the soil. Prune plants to improve airflow and use trellises. Remove infected leaves immediately and destroy them.

Bacterial Diseases

Bacterial diseases like bacterial spot, bacterial speck, and bacterial canker can also lead to rotting fruit. These bacteria thrive in warm, wet conditions. Overhead watering spreads the bacteria from leaf to leaf.

Infected tomatoes develop small, water-soaked spots that slowly enlarge. The spots often have a greasy or scab-like appearance. Fruit infected with bacterial diseases rots quickly on the vine.

Prevent bacterial infections by:

• Purchasing resistant tomato varieties
• Rotating planting areas to avoid pathogen buildup
• Staking and pruning plants for better airflow
• Avoiding overhead watering and working amid wet plants
• Applying copper fungicide sprays as a preventative

Catch infections early by scouting for symptoms daily. Remove and destroy affected leaves and fruit immediately.

Environmental Stress

Environmental factors like extreme heat, flooding, and drought can stress tomato plants. Stressed plants are more vulnerable to issues like blossom end rot and disease.

Erratic irrigation during periods of abnormal weather makes matters worse. Stressed plants have difficulty supplying nutrients like calcium to developing fruit, increasing the likelihood of disorders like blossom end rot.

Ensure plants have adequate moisture during heat waves or drought. Provide temporary shade structures if temperatures exceed 90°F for prolonged periods. Avoid overwatering during heavy rains, which encourages fungal and bacterial problems.

Proper nutrition is also important for environmental stress tolerance. Fertilize plants according to soil test recommendations before planting and side dress with nitrogen mid-season. Mulch around plants helps maintain soil moisture and temperature.

Sunscald

Sometimes green tomatoes exposed to full sun can develop sunscald, which appears as yellowish blistered patches on the skins. Provide afternoon shade if tomatoes are getting sunburned. Or grow heat-tolerant varieties less prone to sunscald issues.

Rodent or Bird Damage

Tomatoes with small holes, nibbled areas, or scarring may be getting damaged by pests like birds, squirrels, chipmunks, or rats. Protect plants with netting and traps where appropriate. Pick tomatoes as soon as they start to show color to avoid letting them ripen on the vine.

Preventing Green Tomatoes From Rotting on the Vine

While some environmental factors are out of your control, you can take these proactive steps to prevent green tomatoes from rotting in your garden:

Water Deeply and Consistently

Inconsistent watering often leads to issues like blossom-end rot. Tomato plants thrive with 1-2 inches of water per week from irrigation and rainfall. Water deeply, especially during hot and dry spells. Consider using drip irrigation or soaker hoses to target the roots. Mulch also helps maintain consistent soil moisture.

Moisten soil to a depth of at least 6 inches. Allow the surface to dry slightly between waterings, then water thoroughly again. Avoid dramatic shifts from saturated to dry conditions.

Choose Resistant Varieties

When buying tomato plants, look for varieties labeled V, F, and N. The V indicates resistance to verticillium wilt, F indicates resistance to fusarium wilt, and N indicates resistance to nematodes. These disease-resistant varieties are less prone to issues like early blight and bacterial infections.

Some great disease-resistant tomato varieties include:

• Better Boy
• Celebrity
• Champion
• Early Girl
• Jet Star
• Roma

Check your local garden center or seed catalogs for other recommended disease-resistant varieties suitable for your region.

Stake and Prune Plants

Staking and pruning tomato plants improves air circulation. Good airflow allows plants to dry out faster after rain or watering, discouraging fungal and bacterial diseases. Prune suckers and remove lower foliage to prevent leaves from touching the soil.

Use tall stakes and tie main stems to them as the plant grows. Prune back lateral shoots and branches to just a few leaves beyond the fruit clusters. Remove any leaves or branches in prolonged contact with soil.

Rotate Plantings Yearly

Avoid planting tomatoes in the same spot each year. Crop rotation prevents a buildup of disease organisms and nutrient deficiencies in the soil. Rotate tomato growing areas yearly with other veggies from different plant families.

Good rotational crops to alternate with tomatoes include:

• Beans
• Carrots
• Onions
• Cucumbers
• Leafy greens
• Squash

Apply Organic Fungicide

Organic fungicides containing Bacillus subtilis or copper can help prevent blights and other fungal issues. Apply these sprays preventatively every 7-10 days once fruit begins developing through the harvest season. Always follow label directions carefully.

Stick to fungicides approved for organic gardening. Conventional fungicides may kill beneficial soil microbes. Rotate between different fungicidal active ingredients for maximum effectiveness.

Check Soil Nutrients

Before planting, test your soil and amend based on recommendations. Tomatoes need proper levels of key nutrients like nitrogen, phosphorus, potassium, calcium, and magnesium for best growth and fruit development. Addressing soil deficiencies provides the nutrients plants need.

Watch carefully for signs of nutrient deficiencies like yellowing leaves or stunted plants. Side dress with a balanced organic fertilizer or specific amendments as needed based on soil test results and plant appearance.

What to Do if You Notice Rotting Green Tomatoes

Even if you follow best practices, you may occasionally notice rotting green tomatoes. Here’s what to do:

• Remove and destroy affected fruit immediately to prevent disease spread. Discard in sealed bags, not your compost pile.
• Prune all affected leaves and stems at least 6 inches below signs of infection, cutting above a node or branch junction. Sterilize pruning shears between each cut with a diluted bleach solution to avoid transmitting diseases.
• Spray the remaining foliage thoroughly with an OMRI-listed organic fungicide according to label directions. Ensure full coverage of both upper and lower leaf surfaces. Reapply every 7-10 days.
• Reassess your recent irrigation, fertilization, and pruning practices. Make adjustments as needed going forward. Did you miss a weekly watering? Have nutrient levels changed? Is more pruning needed?
• Monitor plants extremely closely for signs of new infections like spots, wilting, bronze discoloration, etc. Take prompt action at the first indication to get ahead of outbreaks. Early intervention can often get symptoms under control before they proliferate.
• Remove whole infected plants immediately if more than 30% of fruit shows symptoms. Promptly discard diseased plants in sealed bags. Healthy tomatoes nearby can still be saved!

With quick, decisive action, you can often stop diseases and disorders from spreading. But delayed responses give problems a foothold to spread rapidly.

Wrapping up!

Growing lush tomato plants and harvesting bushels of juicy red tomatoes brings great satisfaction. But seeing your green tomatoes rotting on the vine before they ripen can be very discouraging after all the effort put into care and cultivation.

Issues like blossom end rot, early blight, bacterial diseases, and environmental stress are common culprits behind green tomatoes rotting on the vine. Pay close attention to your plants’ growing conditions. Ensure consistent irrigation, use resistant varieties, stake, and prune plants, rotate plantings, and apply organic fungicides as needed.

Taking proactive care measures goes a long way toward preventing unripened fruit from rotting. Be vigilant in monitoring your tomato patch daily. Take prompt action at the first sign of problems. Remove diseased fruit and foliage immediately to prevent spread.

With proper preventative care and quick response to emerging issues, you can tip the balance in favor of ripe, flavorful tomatoes to enjoy all season long. The delight of harvesting basket after basket of crisp, juicy tomatoes is well worth the extra care and attention.

References:

1. University of California Division of Agriculture and Natural Resources. “Tomatoes: Preparing Garden Soil, Planting, Care and Harvest.” http://ipm.ucanr.edu/PMG/GARDEN/VEGES/tomatoes.html
2. Clemson University Home & Garden Information Center. “Blossom End Rot of Tomato.” https://hgic.clemson.edu/factsheet/blossom-end-rot-of-tomato/