How to manage greenhouse peppers according to plant appearance

For greenhouse peppers from the seedling stage to the full fruiting stage, whether the environment such as temperature, light, soil nutrients and moisture is suitable can be shown by the plant's appearance. During the seedling stage, cotyledons that are small and slender are caused by high nighttime temperatures and a small day-night temperature difference, and the symptoms become more obvious when light is insufficient. If not adjusted in time, the hypocotyl will elongate and the cotyledons will turn yellow and fall off early. After the two cotyledons unfold, lowering the nighttime temperature and increasing the day-night temperature difference can make the cotyledons broad, with the hypocotyl about 3 cm long.

When the two true leaves have fully unfolded and the 3rd true leaf is unfolding, flower buds form inside the plant and it enters the reproductive growth period. Too low a nighttime temperature easily forms three-branch branching, and sometimes two lateral branches combine within 1 lateral branch to become incomplete branching. Only under relatively low temperatures and good nutritional conditions can the plant grow robustly and form three-branch branching; under high temperatures or insufficient light, three-branch branching is very difficult to produce. Therefore, during pepper seedling raising, it is necessary to control a suitable temperature during the day, appropriately lower the temperature at night, uncover early and cover late, strive to get more sunlight, and appropriately expand the nutritional area of the seedlings. During the fruiting stage, as the number of leaves and leaf area increase, the number of branchings and flowerings also increases. If there is too much nitrogen fertilizer, the upper young leaves appear uneven and the leaves shrink.

Sometimes this state also appears when harmed by red spider mites. The midrib of the functional leaves in the middle of the plant protrudes, forming a double boat-bottom shape, and then the leaves in the upper part become distorted; the leaves are all relatively large, and the petioles are also long. From the leaf shape, when nitrogen and phosphorus fertilizers are suitable, the leaves are triangular with a long tip; when potassium fertilizer is sufficient, the leaves are broad and slightly round. High temperatures make petioles long; low temperatures make petioles short and the leaves droop. When soil moisture is insufficient, the petioles bend and the leaves droop; when soil moisture is excessive, the petioles spread open.

The drooping of the entire leaf is caused by weak roots, with most of the nutrients and growth hormones in the aboveground part accumulating in the parts above the root crown, so the petioles grow upward and bend. In addition to excessive soil moisture, too much fertilization and roots suffering from disease also cause this situation. Poor plant growth, with yellowing starting from the lower leaves, is the result of root damage in addition to insufficient nitrogen fertilizer.