How Cold is Too Cold for Tomato Plants Outside

Tomato plants are a warm weather crop and can be sensitive to cold temperatures. While they can tolerate some cool weather, there is a limit to how low the temperature can go before it affects their growth and development. So, how cold is too cold for tomato plants outside?

Temperature Tolerance of Tomato Plants

Tomato plants can tolerate temperatures as low as 45°F (7°C) without injury. However, their growth and development slow down considerably at temperatures below 50°F (10°C). If the temperature drops below 40°F (4°C) for an extended period of time, it can cause irreversible damage to the plants.

Tomato plants prefer temperatures between 70-80°F (21-27°C) during the day and 60-70°F (15-21°C) at night. These temperatures provide the optimum conditions for germination, growth, and fruit set of tomato plants. When the temperature exceeds 90°F (32°C), it can cause excessive wilting and damage to the flowers and fruit.

Protecting Tomato Plants from Cold Weather

If the temperature drops below the ideal range for tomato plants, there are several ways to protect them from the cold, such as:

Cover the plants with a frost cloth or plastic sheeting to trap the warm air around the plants.

Place a heat source, such as a space heater or light bulb, near the plants to raise the temperature.

Mulch around the base of the plants to insulate the roots from the cold.

Water the plants with warm water in the morning to raise their temperature.

It's important to remember that tomato plants need good air circulation to prevent mold and disease, so don't cover the plants for an extended period of time.

Conclusion

While tomato plants can tolerate some cool weather, they prefer warm temperatures for optimal growth and fruit set. Temperatures below 50°F (10°C) can slow down their growth, and temperatures below 40°F (4°C) can cause irreversible damage to the plants. Protecting the plants from the cold by covering them with a frost cloth or plastic sheeting, placing a heat source near them, mulching around the base, and watering them with warm water can help them survive the cold weather. However, it's important to remember to provide good air circulation to prevent mold and disease.