Why Do My Cucumbers Bloom But Don’t Produce?

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Why Do My Cucumbers Bloom But Don’t Produce? There is nothing better than harvesting fresh crunchy Cucumbers in Summer. Cucumbers can be prolific once they get doing. However, you may also observe Cucumber blossoms shrivelling up, without setting fruit, despite being placed in rich soil, and watered regularly.

The main reason this occurs, is that the fruit has not been pollinated, and as a result, the plant does not put additional energy into developing that fruit, because no seeds will develop. There can be a couple reasons this occurs;

  1. The number of pollinators present is low, or they are inactive. (this can occur in rainy weather.
  2. The variety of Cucumber being grown is a Gynoecious type, which is a hybrid seed, that only produces female flowers on the plant.

To determine what is causing the issue, look for male flowers on the Cucumber (there is an explanation on how to determine the difference between male and female flowers, later in the article).

If there is an absence of male flowers, you need to plant a second variety of Cucumber that produces male flowers (Monoecious type). If male flowers are present, hand pollination will be required to ensure the production of fruit.

How Do The Types Of Cucumbers Effect Cucumber Production?

Cucumbers can be divided up into 3 types Monoecious, Gynoecious and Parthenocarpic. Depending on the type of Cucumber, you may need more than one Cucumber plant for pollination and fruit. 

Monoecious types, produce both male and female flowers on the plant. However, despite the plant producing both male and female flowers, they do not necessarily produce flowers at the same time. It is common in Cucumbers, for the male flowers to appear first, sometimes a week or two, prior to the female flowers appearing.  This timing difference can sometimes result in poorer pollination.

Gynoecious types, generally have only female flowers on the plant, though in some cases, a few male flowers may appear. The primary advantage of these types of Cucumbers, is that it produces more female flowers, which provides an opportunity to get a higher yield per plant. These types are commonly used in commercial production for this reason.

The disadvantage of Gynoecious varieties, is that it is not self pollinating and requires a second variety for pollination, as there no male flowers (or very few present on the plant). Additionally, the majority of these types of plants are F1 Hybrids, which prevents you from collecting the seeds for the following year. To learn more about this, go to https://planyourpatch.com/what-is-an-f1-hybrid-seed/.

Some examples of Gynoecious Cucumber varieties include Bristol, Citadel and Olympian.

Parthenocarpic type is a Cucumber that can produce fruit without pollination, however, the fruit produced contains no seed. The primary benefit of this variety, is that you can get fruit without the need for pollination, which is advantageous when growing Cucumbers in a green house.

The key disadvantage is that there are no seeds in the fruit, which does not allow seeds to be saved for the following year. A couple of common Parthenocarpic varieties are Sweet Success, Diva, Nokya, Tasty Jade and Telegraph.

There is a wide variety of Cucumber varieties available in the US from Seeds Now and Seeds for Generation that are all heirloom varieties. This will allow you to save the seeds for the following year. In the UK Thompson & Morgan offer a wide range of seeds.

How Do You Tell The Difference Between Male And Female Flowers?

The easiest way to tell if a flower is a Female, is it will have a small undeveloped fruit that is sitting behind the flower. The fruit will not develop unless pollinated. Additionally, the flower will appear by itself, not in a cluster of flowers.

Male Cucumber flowers have shorter and thinner stems supporting the flower, and they often appear in groups of 3 to 5 flowers.  Their sole job is to provide pollen for the female flowers, they will not produce any fruit. Some examples of Monoecious varieties include Marketmore, Itachi Lemon and Striped Armenian.

How To Hand Pollinate Cucumbers

The easiest way to hand pollinate Cucumbers is by using a fine paint brush. The paint brush is an effective tool for transferring pollen from Male to Female flowers, and example of the type of brush is shown in the picture below.

Steps To Hand Pollinate Cucumbers

  1. To pollinate, locate the Male Flowers on the Cucumber vines. Gently push the brush into the center of the flower, rotating it a few times to pick up as many pollen grains as possible.
  2. Place the brush with the collected pollen onto the central part of the Female blossom, and gently move the tip of the brush over the flower. This will ensure that the pollen grains have transferred onto the Female flower.
  3. Dip the paintbrush into another Male Flower, and continue the pollination process. Normally, there is many more Male Flowers than Female Flowers, however, if this is not the case, it is possible to return to the same Male Flower, to get additional pollen.

Alternatives To Hand Pollination

An alternative to hand pollination, is using a “Blossom Set” spray to pollinate your Cucumbers available on Amazon.  This spray provides Kinetin, a plant hormone, which causes flowers on Cucumbers to produce fruit, without pollination. It is best to apply it once a week, to the flowers and surrounding foliage when flowers appear.

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