Why Tomato Leaves Curling Upwards Is Cause For Concern

Tomato plants are one of the stars of the summer vegetable garden, grown by the vast majority of gardeners. Unfortunately, this beloved crop can come with some challenges, and one of the most common ways tomato plants show they're struggling is by curling their leaves. While there could be a variety of reasons why your tomato plant has curling leaves, leaves that curl upwards, especially if there is no yellowing or twisting, are most commonly due to environmental stress. 

While it may be a relief to know that these upward and inward curled leaves are less likely to be caused by herbicide overspray or viruses, it's still important to figure out how to improve your plant's environment so it can thrive. A careful examination should help you figure out if your plant is in need of more water or is struggling due to overexposure to heat or cold. 

Luckily there are solutions for leaf curling issues. While tomatoes have a reputation for loving the heat, daytime temperatures over about 85 degrees Fahrenheit can be overwhelming for them. If high temperatures are the likely culprit, then a shade cloth can help shade your plants from the brutally hot sun. Similarly, temperatures below 50 degrees can be too chilly. Consider using row covers or even old blankets to protect your plants on these nights. 

If temperature extremes are unlikely to be causing the curls in your tomato plant's leaves, then it's time to take a hard look at how you're watering your tomatoes. Once your tomatoes are established, you should be watering them deeply, but not daily. Tomato plants generally only need around an inch of water per week. If the soil about 4 inches down is still moist, then you can hold off on watering. And don't forget the importance of mulch for helping to regulate not just moisture levels, but also temperature. This can easily be the difference between stressed tomato plants and happy plants with healthy, uncurled leaves.