If you grow your own tomatoes and notice that their leaves are curling, you may wonder what curling tomato leaves mean. Curling tomato leaves is a very common issue with tomato plants. What makes it worse is that one condition that causes it doesn’t result in any long-term damage, and the other condition that causes it may result in serious injury to the plant. You will want to quickly determine the cause of the curling leaves so that you can remedy the problem.
When there’s a ton of moisture in the air, like during rainy season, leaf curl can result. Too much water enters and remains in the soil, resulting in the plant roots being exposed to sitting water for too long. The tomato leaves respond by rolling upwards. The leaves end up curling upwards into a cup-like shape. As time goes by, the leaves’ margins end up touching or overlapping, creating a rolled-up appearance. If you touch the leaves, they’ll feel leathery to the touch. You may end up with nearly all of your foliage being affected. In spite of all of this, the overall health of the plant doesn’t seem to be affected. The plant continues to grow as normal, and the amount of fruit produced is not diminished. Tomato plants that are staked or over-pruned seem fall victim to this phenomenon the most. To prevent this from happening, make sure the soil around the tomatoes remain well drained, and take measures to protect them from sudden and heavy rainfall.
On the flip side, herbicides can also cause incidences of leaf roll, and they are potentially more damaging to your tomatoes. Herbicides end up distorting the leaves and the fruit. One herbicide that causes particular damage is 2,4-D. The leaves become thickened and grow downwards, creating a cup-like shape. Any new leaves that grow in are skinny and don’t unfurl, instead remaining twisted. The tomatoes that grow in are misshapen and distorted with holes, and they don't grow. This condition results in something called a "catfaced" tomato. If herbicide is the problem, the plant will also probably experience some yellowing. If you catch the problem early enough, cease all spraying of herbicide in the vicinity of the tomatoes. This includes avoiding using the grass treated by herbicide as mulch. The plant should be able to outgrow the condition if you catch it in time and handle the plants with kid gloves going forward.