Why tomato leaves curl: three causes and fixes

A Novosibirsk agronomist has explained why tomato leaves curl. Summer gardeners fear they may lose their harvest because of it. We look into how to save the plants and whether anything needs to be done, together with the agronomist.

Heat or resource depletion

High temperatures force plants to react to the threat of excessive moisture loss. Tomatoes are able to close the stomata on their leaves in hot weather.

«There is nothing terrible about tomatoes curling up during the day at +30 degrees Celsius (+86 degrees Fahrenheit). When it gets cooler, they will open again. This can often happen in a greenhouse too because of the high temperature. There are no special measures you can take here. The greenhouse should be open, and the bushes should be watered on time,» noted Lyudmila Shubina, an agronomist and candidate of agricultural sciences.

A leaf loses color and shape when it has exhausted its resource. Now all the green mass should be cut off at least up to the third truss.

Varietal characteristics

Some large-fruited varieties have a tendency to curl their leaves early, that is, before they are fully spent.

The agronomist noted that for «Bull«s Heart», «Danko», and «Eagle»s Eye», having curled green mass in August is more the norm than an unusual reaction.

Diseases or herbicides

A viral disease can take hold in a greenhouse. In this case, a mosaic pattern can be seen on the leaves, and the top of the plant turns into a clump of green mass. The stem then begins to turn black. In this case, all affected bushes must be urgently removed and burned.

«Curling of all the leaves and even the stem of a plant can occur due to the use of herbicides. Here summer gardeners fight weeds that way, then mow that grass and bring it into the greenhouse. That, of course, must not be done,» the specialist emphasized.

Earlier, the agronomist explained what to do if the bark on apple trees cracks and scab appears.