August 20, 2025, 3:04 pm | Read time: 3 minutes
Zucchini is one of the most popular summer vegetables and is not only available in supermarkets but can also be grown in your own garden. When growing your own, it often happens that you either harvest dozens of zucchinis or the fruits spoil on the plant. A common problem is that the zucchini becomes soft and rots at the tip, known as blossom end rot. myHOMEBOOK explains which care mistakes can lead to a zucchini rotting at the tip.
How Does Blossom End Rot Occur in Zucchini?
No fungus or pest is responsible for blossom end rot. It is a physiological disorder that can be caused by a calcium deficiency.
Calcium Deficiency
Calcium is essential for cell structure and the stability of cell walls. It is also important for water regulation in the plant. If the blossom end does not receive enough calcium, the cells become unstable and burst. This can be seen in black, sunken spots. Hobby gardeners should ensure that zucchinis are provided with a balanced fertilizer.
Uneven Water Supply
Even if there is enough calcium in the soil, a deficiency can still occur. Water is necessary for calcium to reach the plant and be transported within it. An uneven water supply is a hindrance. Zucchinis grow quickly. Especially during the growth phase, they should be regularly and evenly watered. If there is too little water, the tip suffers first.
Particularly during the growth phase and in hot weather, it is important to ensure the plant receives enough water.
Root and Soil Problems
Too much water can also be harmful. If the roots remain in dense, wet soil for too long, it can lead to waterlogging and root rot. With damaged roots, the zucchini plant can absorb less water and nutrients. A possible consequence is that the zucchini rots at the tip.
Also interesting: 4 Reasons Why Zucchini Leaves Turn Yellow
Imbalance with Other Nutrients
A balanced fertilizer is essential for harvesting delicious, crunchy zucchinis. An unbalanced fertilizer, such as one with too much potassium, magnesium, or ammonium, can block calcium absorption.
Overfertilization with Nitrogen
Nitrogen, like calcium, potassium, or magnesium, is an important plant nutrient. Zucchinis should also receive enough nitrogen—it is important for the plant’s growth. However, too much can be harmful. An excess of nitrogen leads to unbalanced growth in most plants, including zucchinis. This is also known as “leggy growth.”
With excess nitrogen, the plant grows too quickly and invests a lot of energy in developing shoots and leaves. Fruit development, however, is neglected. Less water and nutrients reach the fruits. As a result, the plant tissue becomes soft and more susceptible to diseases and rot.
Lack of Pollination
A lack of or insufficient pollination can also lead to rotting tips in zucchinis. It can happen that a zucchini begins to grow even though it was not or only partially pollinated. The fruit initially develops normally, but then suddenly stops growing and begins to rot at the tip.
To prevent this, garden owners should create a bee- and insect-friendly garden. This includes planting flowering plants, avoiding chemical pesticides, and providing nesting sites and water sources. Alternatively, the plant can be pollinated by hand.