Why do tomato flowers turn yellow before they open?

September is the key period for flowering and fruit setting of autumn delayed tomatoes; at this time there are fewer diseases, the temperature is suitable, and it is exactly the period of the year most suitable for vegetable growth. But many vegetable growers report that the tomatoes in their greenhouses turn yellow and drop before they even flower. What is going on? Let's take a look together.

1. Poor weather during the seedling stage

For autumn delayed tomatoes, the seedling raising period is concentrated in July, and this summer had a lot of rain and many cloudy days, making the overall light during the tomato seedling stage on the weak side; high temperature and weak light inevitably lead to thin and weak tomato seedlings. So this year tomato seedlings are generally weak, the seedlings are thin and weak with poor stress resistance, and after transplanting there are few cooling measures in the greenhouse, the greenhouse temperature is high, and many seedlings are scalded, inducing damping-off and other problems. Moreover, the appearance of a harsh environment will induce vegetables to produce substances such as ethylene, which will accelerate the aging and shedding of leaves, flowers and so on, so tomatoes show the phenomenon of turning yellow before flowering.

2. Poor flower bud differentiation

Poor flower bud differentiation is also one of the main reasons for turning yellow and shedding before flowering. A high temperature and weak light environment will weaken photosynthesis, result in less nutrient accumulation, cause the plant to be thin and weak, lead to flower bud abortion, and cause flower drop. Water and fertilizer conditions have a great influence on flower bud differentiation, and many elements play an indispensable role in flower bud differentiation, while many farmers apply large amounts of chemical fertilizer, causing soil nutrient imbalance, increasing soil salinization, and some root systems absorb other elements. In addition, the large and unreasonable application of hormones can easily cause hormone imbalance in the plant body, leading to disordered plant growth.

3. Improper fertilization

Base fertilizer is a key means of improving the soil. Many farmers mostly apply farmyard manure and compound fertilizer as base fertilizer, leaning toward fertilizers such as nitrogen, phosphorus and potassium, but they supplement very little of the medium and trace elements such as calcium, magnesium, iron, zinc, boron and molybdenum, yet these trace elements are closely related to plant flower bud differentiation. The root system is weak during the seedling stage, and applying large amounts of chemical fertilizer will make it difficult to absorb trace elements in the soil, thereby affecting flower bud differentiation and even causing flower bud abortion and flower drop. Generally speaking, in addition to applying fully decomposed organic fertilizer, it is also necessary to pair it well with trace elements and turn them into the soil together with the organic fertilizer to ensure balanced soil nutrients.

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