This is called physiological leaf roll! Fortunately, leaf roll doesn’t affect the growth of the tomato or the fruit.
It’s not caused by an insect or disease but by environmental factors* Environmental factors are anything that causes stress to the plant such as not hardening off properly in spring, excessive moisture or drought, too much nitrogen, hot/cool temperature fluctuations, severe pruning, root damage, wind, transplant shock – alone or in combination. Physiological leaf curl is more common in tomatoes grown outdoors, but can also happen in indoor gardens.
What does it look like?
It usually starts in the lower leaves which may cup upwards and then start to roll inwards. The leaves may become thickened and leathery but stay green. It’s not unusual for the whole plant to become affected. Vine tomatoes (indeterminate) tend to get it more often than bush tomatoes (determinate).
What should you do?
Try using mulch on your plants soil to retain even moisture. Try to water deeply and evenly. Don’t expect the leaves to ‘uncurl’. As long as they are green, your plant will be fine!
Download our “Tomato Problems” PDF for other problems that could crop up specific to tomatoes in your classroom garden.