Healthy plants are the key to a successful harvest. Twisted leaves and tops of tomatoes in the greenhouse indicate problems in the environment or the plant itself. To determine the cause, you need to answer a few questions. Which leaves are twisted: old, new, or all? In which direction: up or down? Are there any other symptoms on the plant, including the tops? Keep in mind that indeterminate tomato varieties are more prone to physiological leaf twisting than bush varieties (determinate).
Causes of tomato leaf curl in the greenhouse upwards
Incorrect watering, excess nitrogen, and phosphorus deficiency, too much pruning, root damage during soil treatment or loosening, early planting, and plant stress during transplanting - all these factors can lead to the curling of tomato leaves.
Signs usually appear on the lower leaves, protruding upwards, after which the leaves curl inward toward the midrib. Affected leaves become thick and leathery but remain a healthy green color. Over time, all plant leaves become twisted.
Gardeners who tightly cover the greenhouse to protect plants from nighttime cooling may encounter the issue of leaf curl due to improper watering. In conditions of high temperatures and aridity, leaf edges may curl upwards, starting with the lower leaves. In this manner, plants protect themselves when they don't receive enough water. This water deficit leads to leaf curling. Twisted leaves absorb less solar energy and lose less water.
Strive to provide the same moisture conditions around the tomato roots. If you are leaving and sunny weather is forecasted, leave the greenhouse slightly open and add a layer of mulch (e.g., from nettles, dandelions, or seedless grass) to the soil to reduce moisture evaporation. Tomatoes will quickly return to normal.
Fertilizing greenhouse tomatoes is not as simple as just adding more nutrients. The issue may be related to pH balance or the interrelation of different nutrients. Be sure to maintain the optimal pH level (usually between 6 and 7) and fertilize plants according to their growth stage. For example, nitrogen is needed before planting, while potassium and phosphorus are needed before flowering.
Tomato Pests in the Greenhouse Can Transmit Viruses
Don't forget to check the underside of the leaves. If your tomatoes are curling, this may be due to stress or dehydration. If this issue is not related to the environment, such as heat or watering, it may be related to pests such as aphids and whiteflies. Although they are more common outdoors, they can also enter greenhouses.
Pay attention to the whitefly, which transmits the tomato yellow leaf curl virus. New leaves become cupped and pale green. The entire plant may slow its growth, purple veins appear under the leaves, and fruiting is below normal.
Tomatoes may also have the presence of the mosaic virus, which causes other symptoms, such as leaf mottling, small leaves, and fruit darkening.
If a virus is the cause, new shoots will twist, not old leaves, as is typical of stressed plants. Remove all infected plants to prevent virus spread. In the future, choose virus-resistant varieties and implement insect protection measures.
Tomatoes and Catch Crops
Flower-vegetable design is becoming increasingly popular, and greenhouse tomatoes are no exception.
An interesting way to determine tomato water deficiency is to plant a dwarf catch crop at the end of rows. This plant grows to about 20 cm in height and is a bright and long-flowering drought indicator. It also does not compete with other plants for water, as it accumulates it in its succulent stems. If you make a mistake in watering, the catch crop will show it by wilting, and you will immediately understand why tomatoes curl upwards in the greenhouse.
In addition, catch crop leaves can be used for a bio-preparation against aphids and other pests. They also contain tryptophan, which stimulates plant growth. To prepare a pest control solution from catch crop leaves, pour three bunches of leaves with cold water and leave overnight. Then use the infusion for spraying.
The catch crop can also be propagated by cuttings or placed in water for root formation.
Thus, the catch crop is an interesting plant that will help you control humidity in the greenhouse and protect your planting from pests. It can also be a wonderful houseplant and a source of seeds for the next season.
