Hi, what causes courgettes to rot after flowering and how can I fix the problem please?

Hi David, that is called blossom end rot and can be caused by nutrient deficiencies of calcium and magnesium. To correct, add a handful of dolomite lime to the soil around the plants. Feed plants with a balanced fertiliser that contains calcium and magnesium such as Tui Vegetable Food. Alternatively, it can be caused by inconsistent watering, it is preferable to water in the morning or early in the day, rather than in the evening as the water doesn't dry out overnight, creating moist humid conditions, increasing the chance of disease affecting the plant. Incomplete pollination can also cause courgettes to rot, encourage bees and other pollinators to the garden by planting flowering plants such as borage and lavender. Check out our courgette growing guide on our website. Blossom end rot isn't contagious, pick off the affected fruit and dispose of in the rubbish, the plant should come right with fertiliser and consistent watering.