The zucchini grows and blooms vigorously, but instead of a rich harvest, the flowers fall off. Many garden and balcony owners know the problem. But why is that and what can you do about it?
Table of Contents
Causes of flower loss
Like all squash plants, zucchini plants ( Cucurbita pepo var. giromontiina ) produce both male and female flowers on the same plant. For a rich harvest, therefore, only a single plant is generally necessary. But sometimes there is no fruiting and the flowers fall off. As a rule, the following causes are mainly responsible for this:
For young plants
In order to guarantee that pollen is also available for pollination when the female flower opens, the squash almost exclusively forms male flowers at the beginning of the growing season. The female counterparts then appear with a time delay. Once a male flower has opened and the pollen has been released, they have done their job and fall off. It is therefore completely normal for young plants to lose their first flowers before fruit has formed.
lack of pollination
In addition to the male zucchini flowers, all female ones that are not pollinated naturally also fall off. The following reasons are possible for this:
Missing Insects
For pollination, zucchini plants need insects that carry the pollen from the male to the female flower. If there are not enough bees, bumblebees, butterflies and the like in the garden, the fertilization rate is poor. There are a few simple tricks to ensure that pollinators find their way into your garden. Fill a few empty corners with flowering plants to attract bees. In addition, it is of course important to offer the animals a place of retreat and not to use insecticides. In the greenhouse, open windows or doors ensure numerous visitors.
Stress
Zucchini plants are quite susceptible to stress and then produce more male flowers than female flowers. The problem: only the female flower produces fruit. Although the pollination rate is high, the harvest is poor. The only reason why so many zucchini flowers fall off is that there are almost exclusively male flowers. Triggers for stress include:
- dryness
- waterlogging
- shortage of nutrients
Regular watering is important so that zucchini can produce enough fruit. You should water the plant extensively at least twice a week, daily on hot days. Preferably water directly on the soil under the plant and do not wet the leaves, otherwise your plant will be susceptible to infection with powdery mildew. If the zucchini plants suffer from drought, the flowers fall off to ensure the survival of the mother plant.
Unfavorable weather conditions
Zucchini plants fruit poorly when the weather is wet and cool. Very humid, warm air also has a negative effect on pollination. In this case, the pollen sticks together and does not reach the female zucchini flower. At temperatures above 30 degrees, the pollen also suffers. The result is unfertilized flowers that dry up and fall off.
Diseases
Much more rarely, an infection with powdery mildew is to blame for the loss of harvest. For prevention, a brew made from horsetail can be used in the natural garden. In the event of an infection, simply cut off the leaves close to the ground and dispose of them in the household waste. A natural secret weapon against powdery mildew can be used in the greenhouse: sixteen-spotted ladybird. Powdery mildew is one of the favorite foods of yellowish insects with white dots.
Fertilize balcony plants manually
If you only grow a single zucchini plant in a tub on the balcony, pollination by insects is less likely than with a whole zucchini bed outdoors. Zucchini flowers only open for a short time in the morning. If only a single blossom or only ones of the same sex are open, the interplay that nature devised does not work. After the female flower has closed again without being fertilized, the fruit set continues to grow a little bit. One gets the impression that fruits are forming, until they suddenly dry up and fall to the ground.
execution
Balcony gardeners should therefore not leave pollination to chance, but pollinate the zucchini plants by hand. This method has an almost 100% success rate and is very easy to do even for inexperienced home gardeners. All you need is a fine cosmetic brush, but if necessary you can also use your finger to transfer the pollen. Gently stroke the brush over the pollen in the male zucchini flower, then dab it on the stigma in the center of the female flower. The fertilization has already taken place and all you have to do is wait.
frequently asked Questions
The shape and size of the zucchini flowers are relatively similar in both sexes. However, if you look at the flower stalk, the male one is long and thin. The female flower, on the other hand, sits directly on the ovary, so that the “stem” appears significantly shorter and thicker. The stalk almost looks a bit like a tiny zucchini fruit.
There are actually cultivars on the market that prefer female flowers. These include the ‘Dundoo’ variety, which was first bred in England. There are also so-called parthenocarpic zucchini varieties that can develop fruit without prior fertilization. So those who want to save themselves work and do not rely on chance should grow such varieties for a bounty harvest. This is especially true for gardeners who only grow a single plant for reasons of space.
