Why do cucumbers in greenhouses develop barren flowers and what can be done?

Reasons for formation

Of course, the appearance of barren flowers is unpleasant, as it's difficult for an inexperienced gardener to identify them, so by the time you realize there won't be a harvest, it's too late to do anything. To avoid getting into trouble and save your cucumbers in time, ask yourself: "Why are there so many barren flowers on my cucumbers? What am I doing wrong?"

One of the reasons for the formation of barren flowers is excessively high temperatures in the greenhouse. As soon as the thermometer shows above 30°C, decisive action is needed. Combined with high humidity, cucumbers have no chance of fruiting in such conditions.

If you have a hybrid variety with female flowers, but there are no insects to pollinate the flowers, or no male flowers, the plant will not bear fruit. Try combining varieties to increase the likelihood of fruit formation.

A lack of nutrients in the soil contributes to the formation of barren flowers or the absence of ovaries altogether. Flowering in cucumbers, like any other plant, requires a significant amount of energy. They obtain the missing nutrients from the soil. If the soil itself is infertile, the plants experience "starvation" and are less willing to devote their remaining energy to fruit formation.

If you've recently fertilized your greenhouse soil with nitrogen fertilizers, you may have an excess of nitrogen in your garden beds. Nitrogen fertilizers are known to promote foliage growth, but they have little effect on flower formation. Avoid applying nitrogen fertilizers just before flowering to avoid interfering with the development of female flowers.

If you're watering cucumbers with cold water, you've likely chilled the plants. Overwatering is also one of the reasons cucumbers produce a lot of male flowers. When planting cucumbers, be sure to consider whether groundwater flows under the greenhouse, as too-cold water negatively impacts the formation of female flowers.

Poor seed quality shouldn't be ruled out. Buy them only from reputable producers and treat them before planting. Seeds harvested this year will likely produce an abundance of male flowers, meaning they will produce fewer female flowers and will delay fertilization and fruiting.

How to get rid of

The answer to the question "why do cucumbers have barren flowers" varies depending on the cause of the barren flowers. Fortunately for gardeners, getting rid of this problem isn't easy, but it is possible if done correctly and, most importantly, promptly.

First, make sure the greenhouse isn't too hot. High temperatures, like high humidity, sterilize cucumber flowers, causing them to abort. High relative humidity makes pollen sticky and heavy, preventing it from moving.

Varieties that require insects for pollination are completely unsuitable for greenhouses. Be sure to select your varieties carefully, as a greenhouse full of sterile cucumbers is not the most pleasant gift at the end of the season.

Take these rules into account:

• Do not use fresh cucumber seeds from the garden for sowing, as they produce fewer female flowers;
• do not sow cucumbers in shaded areas, as cucumbers love sunlight;
• Do not allow cucumber plantings to become too dense, as the abundance of green mass creates abundant shade.

Of course, these rules do not provide a 100% guarantee, but they will help cucumbers develop better.

In most cases, cucumbers in a greenhouse develop as they please—don't let this happen. It's important to regularly pinch the tips around the sixth leaf to stimulate the formation of female flowers. What's the point of pinching during flowering? If you do this shortly before or at the very beginning of flowering, you'll encourage the cucumber plants to form side shoots, which are where the female flowers appear.

If you've overwatered your cucumbers, it's time to give them a dry spell—stop watering for a while. This will prevent them from needlessly and excessively absorbing moisture, and will refocus on producing fruit. Monitor the soil regularly, and avoid sudden changes in water temperature when watering, especially when it's lower than the soil temperature.

If, in addition to the formation of barren flowers, you notice wilted leaves, it's time to fertilize. Mix a mullein infusion (diluted 1:10) with 5 grams of urea and water the beds. Try not to pour the liquid directly under the stems. Another nutrient-rich fertilizer option is a yeast solution. Dilute 10 grams of dry yeast in 10 liters of water, let it sit for several hours, and then distribute the solution at a rate of no more than 1 liter per cucumber plant.

If you suspect there's too much nitrogen in your soil, it's time to make a neutralizing fertilizer. Take 2 tablespoons of superphosphate or another fast-acting phosphorus fertilizer and dilute it in 10 liters of water. Wood ash infusion also works well to neutralize nitrogen. To prepare it, dilute 0.5 liters of wood ash in 10 liters of water and let it sit for 24 hours. Use the resulting solution instead of regular water.

Don't underestimate the power of organic fertilizers, no matter what the "experts" say. The carbon dioxide they produce promotes plant growth and development, especially during flowering. A lack of carbon dioxide can lead to delayed or complete absence of female inflorescences. Line your cucumber beds with mullein, being careful not to let it touch the stems and lower leaves. Regularly loosen the soil around the cucumbers to help them absorb the nutrients they need.

Don't try to remove barren flowers, as these are male inflorescences containing pollen. Firstly, removing male flowers will not result in the formation of female flowers. Secondly, you will damage the plant, which will experience stress from such vandalism. The best method is to pinch off shoots to stimulate the development of female inflorescences.

If you didn't manage to save this year's harvest, it's worth making a note for next year. Before planting, prepare the seeds. This should be done not only for cucumbers, but for all plants in your garden. First, warm them to stimulate the formation of female flowers in the future.

How to warm the seeds? Place the seeds in a cheesecloth bag and hang it near a radiator or heater for 2 months.

It’s better not to take risks and take seeds that are 2 to 4 years old, as they are more productive.

Video: "How to Solve the Problem of Cucumber Barren Flowers"

If you are concerned about the problem of cucumber flowers not blooming, watch this video carefully and follow its advice.