I would like to know why the courgettes, apart from the first ones I collect, turn yellow first at the "tip" then slowly all the way down with the consequence of no growth and therefore preventing a good harvest. In thanking you I take this opportunity to extend my best regards.
the courgettes are very cultivated plants in the garden, simply because the cultivation is easy, and the harvest is very high; a single plant remains in production for months, giving rise to many large and turgid courgettes. It happens to many that the courgettes, however, never reach maturity, turning yellow and wrinkling, after a development that seems normal. The first cause of this behavior is drought, especially during the summer months: the courgettes need regular watering, in summer they should be watered on alternate days, watering the soil thoroughly, so that it remains well moist even in the depths. The soil should be well soaked, and not the foliage, otherwise the development of oidium is stimulated, which becomes quite problematic on the large leaves of the courgettes.
Another problem often present with courgettes is due to fertilizer and soil: these plants absorb very large amounts of microelements and macroelements from the soil; for this reason, before planting courgettes or sowing them directly in the field, it is necessary to work the soil well, adding manure, and also slow release granular fertilizer. The manure will supply a good quantity of nitrogen and will give a better consistency to the mixture of the soil; in addition to nitrogen, the courgettes also require phosphorus, potassium and microelements, such as iron, and magnesium, so it would be advisable to sprinkle a slow-release granular fertilizer of excellent quality on the ground, which in addition to the classic macroelements, NPK, also contains the trace elements; you can find it in the nursery of various types, check on the label that there are many minerals, generally among the products for the vegetable garden you will surely find useful for the courgettes.