Tomatoes often fail to turn red due to several common reasons:
- Temperature extremes are the biggest factor. Tomatoes ripen best between 68°F and 77°F (20°C to 25°C). Temperatures above 85°F (29.4°C) or below 50°F (10°C) can stop or slow ripening and prevent the development of the red pigment lycopene, which gives tomatoes their red color.
- Tomatoes must be fully grown and mature in size before starting to turn red. Immature or undersized fruit will remain green.
- Lack of sufficient sunlight for at least 6 hours daily, or dense foliage shading the fruit, can reduce the energy available for ripening.
- Excessive watering and excessive growth of suckers (side shoots) can divert the plant's energy away from ripening fruit.
- Environmental stresses such as poor soil nutrition, lack of airflow, or weather conditions (like heat waves, smoke haze) can delay or stop ripening.
To help tomatoes turn red, consider:
- Providing shade during heat waves to keep temperatures in the optimal range.
- Ensuring the fruit has matured fully.
- Pruning suckers and some foliage to direct energy to fruit.
- Avoiding overwatering.
- Picking mature green tomatoes and ripening them indoors if outdoor conditions are unfavorable.
These factors combined usually explain why tomatoes in the garden may remain green and not turn red as expected. Patience and adjusting growing conditions can often resolve the issue.
