Leaf curl on tomatoes

I have had a little leaf curl this week, so I thought I would copy a part of what I posted on it last year, as many of you will have some leaf curl as the weather warms up. Basically your plants have had plenty of water, so the root system  has remained fairly small. The plant them cannot take up enough water on hot days, so it curls it's leaves to have less light on them, and it controls the growth of the plant, to concentrate on growing its root system. However, the plant still needs plenty of water at this time of the year, so please do not dramatically decrease watering, unless your plants are going very pale. Like it explains below it  is just creating a larger root system to help cope when it is more laydened with fruit.

Physiological Leaf Curl in Tomatoes.

When tomato plants grow vigorously in mild, spring weather, the top growth often exceeds the root development. When the first few days of warm, dry summer weather hit, the plant 'realises' it has a problem and needs to increase root development. The plant tries to reduce it's leaf area by rolling leaves. The leaves curl along the length of the leaf (leaflet) in an upward fashion. It is often accompanied by a thickening of the leaf giving it a leathery texture. Interestingly, leaf roll is worse on some varieties than others.

This is just a simple case of slight overwatering, nothing to worry about, if you just ease off on the watering a little. At this time of the year it is usually on lower leaves, just try to water more evenly will have a smaller root system. Saying this, under-watering can give you blossom end rot.

This problem usually applies to tomatoes. Unlike potatoes, the curling does not indicate a disease. Inward rolling of young tomato leaves is usually taken as a good sign if the leaves are dark green. The rolling of older leaves is a sign that too much foliage has been removed from the plant or a wide variation of temperatures. The plant shown here looks like it has taken up excessive nutrients, which could be in the compost. It will settle down and should grow out of this.

 Example of unhealthy tomato leaves curling inwards, affected by contaminated manure or spray drift. Notice the very tight curly head, which is a sure sign. More Info