Cucumber Flowers, But No Fruit? (3 Causes You Should Know About)


Are you frustrated by cucumber plants that produce flowers, but no fruit?  If so, you’re probably wondering why it happens, and what you can do about it.

So, why do cucumbers flower but produce no fruit?  A cucumber plant will flower but produce no fruit if there is a lack of either male or female flowers on the plant. A lack of fruit will also occur due to poor pollination. Growing conditions (such as temperature, weather, and nitrogen levels) also affect pollination and flower production.

Sometimes, it just takes patience to get fruit from your cucumber plants.  However, there are times when you can take steps to help your cucumber plants with their fruit production.

In this article, we’ll talk about why a cucumber produces flowers but no fruit. We’ll also give you some ideas on what you can do to solve the problem.

Let’s get started.

Why Do Cucumbers Flower But No Fruit?

There are several possible reasons that your cucumber plant will produce flowers, but no fruit.  Some of the causes are:

  • Lack of female flowers (cucumbers have male and female flowers – and male flowers appear first)
  • Lack of male flowers (in gynoecious cucumber varieties, there are mostly female flowers)
  • Lack of pollination (not enough bees and other pollinators)
  • Temperature & weather (too cold, too hot, or too rainy)
  • Nitrogen Levels In Soil (too much nitrogen reduces flowering)
female cucumber flower
If you see cucumber plants not producing fruit, a lack of female flowers (shown here) is a common cause. A lack of pollination is another reason for a lack of fruit set on cucumber plants.

This YouTube video I made gives a summary of the causes and solutions for flowers (but no fruit) on cucumber plants (you can also watch the video below).

A lack of female flowers is the most common reason, and often is not a cause for concern.

Lack Of Female Flowers

It is important to remember that most cucumber plants are monoecious.  This means that the male and female flowers are found on the same plant.

cucumber flower female
Cucumber plants have male and female flowers (a female flower is shown above, along with a fruit that is already forming).

According to UC Davis:

  • male cucumber flowers are found on shorter stems, and grow in clusters of 3 to 5.  They produce pollen, but no fruit.  The stem behind a male flower is thinner.
  • female cucumber flowers are found on longer stems, and come in single flowers rather than clusters.  They cannot produce pollen, but they have a small fruit behind the flower.  This makes the stem behind a female flower look thick and swollen.
female cucumber flower 2
A female cucumber flower has a swollen stem behind it (which will grow into a fruit if proper pollination occurs).

You can see pictures of both male and female cucumber flowers on the South Dakota State University Extension website.

On monoecious plants, male and female cucumber blossoms are produced in about equal numbers.  However, the catch is that they are not produced in equal numbers at the same time.

cucumber flowers
Male cucumber flowers often appear on the plant before female cucumber flowers.

According to the New Mexico State University:

“The time between the first development of male flowers and the female flowers depends on plant variety and environmental conditions. Your problem may just be that the female blossoms have not formed yet.”

https://aces.nmsu.edu/ces/yard/2008/072608.html

On cucumber plants, male flowers appear earlier than female flowers.  Early in the growing season, the plants put their energy into producing male flowers first.

cucumber flower
Without female blossoms, cucumber plants cannot produce fruit. Female flowers come later in the season, after males have already blossomed.

This ensures that there is enough pollen present for the female flowers when they arrive later in the season.  In fact, according to the Old Farmer’s Almanac:

“They often begin producing male flowers several weeks before the females appear.”

https://www.almanac.com/fact/why-wont-my-cucumber-plants-produce-fruitsr

Male flowers only stay on the plant for about a day, and then they fall off.  Needless to say, this can be discouraging for both new and experienced gardeners alike!

cucumber flower 2
Male cucumber flowers only stay on the plant for about a day before they fall off. Don’t be discouraged, since this is normal, and the plant will produce more!

However, it is not a cause for concern, at least not right away.  Some of the earliest male flowers on a cucumber plant will fall off before any female flowers appear.

If your cucumber plant only has male flowers, it is probably because it is too early in the season for the female flowers to appear. If there are no female flowers on your cucumber plant later in the season, then it might be time to investigate why (and try to solve the problem).

How To Increase Female Flowers In Cucumbers

Cucumber plants should start producing a crop of fruit once the female flowers start to appear.  However, if you planted too late, high temperatures could cause some of the female flowers to abort.

Cooler temperatures encourage female flowers to form sooner and stay on the plant.  However, cooler temperatures may discourage formation of male flowers early in the season.

thermometer
High temperatures discourage female flowers from forming on cucumber plants.

According to the Iowa State University Extension:

“In the case of cucumbers, squash, and pumpkins, cool temperatures promote development of female or perfect flowers at a node closer to the base of plant, and the ratio of male to female flowers is reduced. Generally high temperatures promote male flowers, and delay female flower development.”

https://hortnews.extension.iastate.edu/2016/07-29/cucurbits.htm

So, if you want to increase female flowers in cucumbers, keep your plants cool!  To encourage female cucumber flowers, plant them outside where it is cooler (not in the greenhouse).

greenhouse conservatory
A greenhouse might be too warm for a cucumber plant if you want to encourage female flowers.

If necessary, give them a little shade during the hottest part of the day to protect them from the sun’s heat. You can learn more about sunlight for cucumber plants in my article here.

One other option to increase female flowers in cucumber plants is to cultivate mostly gynoecious varieties in your garden.

female cucumber flower 3
Choose gynoecious cucumber varieties to get more female flowers. Just make sure that you have some regular varieties so that you get enough male flowers!

This will give you more female flowers, but it may cause another problem: lack of male cucumber flowers. Let’s talk about that problem next.

If your female cucumber flowers are falling off the plant, it is probably because they were not pollinated properly. According to the University of Nebraska Extension, cucumber flowers are only open and available for pollination for about a day.

bee
If bees don’t pollinate a female cucumber flower in time, it will fall off the plant and not produce fruit.

After that, they will fall off if not pollinated properly. To avoid this, ensure proper pollination (more on this later!)

Lack Of Male Flowers

On the other hand, a lack of male flowers on a cucumber plant can also be a problem.  Although this is less common than a lack of female flowers, it can still happen.

A lack of male flowers is most likely to happen with gynoecious cucumber varieties.  A gynoecious variety is one that produces mostly (or all) female flowers and very few (or no) male flowers.

female cucumber flower
A gynoecious cucumber plant produces few or no male flowers.

The good thing about gynoecious cucumber plants is that they produce more female flowers.  This gives them the potential to produce a lot more fruit in a season.

The downside is that gynoecious cucumber plants need a nearby plant with male flowers on it to produce fruit. The reason is that there will be few or no male flowers on a gynoecious cucumber plant.

How To Increase Male Flowers In Cucumbers

One solution is to plant your garden with mostly gynoecious cucumber plants.  Then, plant a small number of seeds from a different cucumber variety that is monoecious.

cucumber seeds
To increase male flowers in cucumbers, raise the temperature and plant some seeds from monoecious varieties.
Image courtesy of user:
Gaurav Dhwaj Khadka via: Wikimedia Commons: https://commons.
wikimedia.org/wiki/File:
Cucumber_Seeds.jpg

This will ensure that there are enough male flowers (from the monoecious plants) to provide plenty of pollen.  It will also give you lots of fruit (from the gynoecious plants).

Also remember that higher temperatures encourage male flowers to form.

Lack Of Pollination

Even if you have plenty of male and female flowers on your cucumber plant, there could still be a delay in setting fruit. This is because cucumbers are not self-pollinating: they need bees to carry pollen from male to female flowers.

cucumber fruit from flower
To produce fruit, a cucumber plant needs bees to pollinate the flowers.

Without proper pollination, you could have lots of flowers with no fruit set.  According to the New Mexico State University:

“If you see the female flowers on your cucumber plants, but they are not “setting” fruit, then the problem may be that you do not have pollinators.”

https://aces.nmsu.edu/ces/yard/2008/072608.html

Often, bees are the ones to carry pollen from male flowers to female flowers to pollinate cucumber plants.

bumblebee
Bees often do the work of carrying pollen from male flowers to female flowers on cucumber plants.

However, you may have a lack of bees in your yard due to use of pesticides (by you, a neighbor, or a nearby business).

Do Cucumbers Self Pollinate?

Unlike tomatoes, cucumbers are not self-pollinating.  Something needs to carry pollen from the male flower to the female flower to start fruit production.

In most cases, bees and other pollinators fill this role.  However, you can do it yourself if the need arises!

How To Hand Pollinate Cucumber Flowers

There are several ways to hand pollinate cucumber flowers.  You can use:

  • a soft-bristled brush (such as a paintbrush or toothbrush)
  • a cotton swab
  • the male flower itself (break it off and touch the stamens inside the male flower to the inside of the female flower.  Don’t feel bad about doing this – the male flowers will fall off anyway, and besides, they cannot produce fruit!)
electric toothbrush
A toothbrush is one way to hand pollinate cucumber flowers. It doesn’t need to be an electric toothbrush.

The idea is to get the pollen from the inside of the male flower to the inside of the female flower.  To do this, there are some things to keep in mind.

According to UC Davis, you should only use freshly opened male flowers, and you should hand pollinate early in the day.

cotton swab
You can also use cotton swabs to help you pollinate cucumber flowers by hand.

Look for the newest male flowers that have appeared on your plants.  This will increase your chances of success with hand pollination.

According to the New Mexico State University:

“Each morning collect pollen from the stamens in the center of the male flowers and then transfer that pollen to the stigma in the center of the female flowers. Use a small, soft bristled paint brush to do this. If you are successful, you should see small cucumbers forming within a few days.”

https://aces.nmsu.edu/ces/yard/2008/072608.html

How Long After Flowering Do Cucumbers Appear?

The time to fruit maturity will vary, depending on the type of cucumber.  According to the Michigan State University Extension:

  • small pickling cucumbers (1 inch diameter or less) take 4 to 5 days to mature
  • large pickling cucumbers (2 inch diameter) take 8 to 10 days to mature
  • slicing cucumbers take 15 to 18 days to mature
pickling cucumbers
Pickling cucumbers are smaller and take less time to mature than slicing cucumbers.

You can learn more about when cucumber plants produce fruit in my article here.

Just remember that temperature plays a big role in pollination, and whether you will need to do it yourself.

thermometer
Temperature plays a big role in cucumber flower pollination. If it is too cold, the bees won’t work!

If temperatures are too cool, bees won’t come out to work.  If temperatures are too hot, female flowers may abort, preventing pollination.

Temperature & Weather

As mentioned earlier, temperature matters when it comes to flower formation for cucumber plants.

Cold temperatures can damage cucumber plants.  Frost will spell the end for cucumbers, and temperatures below 50 degrees Fahrenheit (10 degrees Celsius) will cause slow growth or damage to plants.

frost
Frost will spell the end for cucumber plants, and cold (under 50 degrees Fahrenheit) will damage them.

When it is hot, a cucumber plant tends to produce more male flowers.  At cooler temperatures, a cucumber plant produces more female flowers.

The variety of cucumber also affects how the plant responds to different temperatures.  The variety also matters in terms of when a cucumber should be planted, how long it will take to form flowers, and how long the fruit takes to mature.

Vining varieties produce more fruit and take up more space.  Bush varieties produce fruit a little bit earlier in the season than vining varieties.

cucumber plants
The variety of cucumber also affects the plant’s response to temperature changes.

Both types can benefit from support, such as a trellis.  You can learn how high cucumbers will climb (plus how to support them) in my article here.

Weather also plays a role in flower formation.  For example, rainy weather may stop bees from doing their work.  This will result in fewer pollinated flowers and less fruit.

Nitrogen Levels In Soil

Cucumbers are heavy feeders, especially when it comes to nitrogen.  However, it is possible to have too much of a good thing.

Excessive amounts of nitrogen can burn plants, especially when applied all at once.  However, too much nitrogen can have another effect on cucumber plants: delayed production of flowers.

soil test kit
Get a soil test to determine pH and nutrient levels before you add fertilizer to your garden.

According to the Iowa State University Extension:

“High nitrogen fertilization can also delay production of female flowers. Heavy nitrogen application will often lead to vines remaining vegetative for longer periods of time, producing female flowers only later in the season.”

https://hortnews.extension.iastate.edu/2016/07-29/cucurbits.htm

In other words, too much nitrogen causes green growth at the expense of flowers and fruit.  Too much nitrogen can also worsen the problem of a lack of female flowers on cucumber plants.

Excessive nitrogen is often caused by heavy application of high-nitrogen manure or concentrated fertilizers with a high nitrogen content.

manure
You can burn plants with too much manure. High levels of nitrogen can also delay female flower formation on cucumber plants.

Conclusion

Now you know why your cucumber plant is producing flowers but no fruit.  You also know what you can do about it.  Just remember that sometimes, patience is all it takes!

You might also want to read my article on why cucumber plants wilt after transplant.

I hope you found this article helpful.  If so, please share it with someone who can use the information.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

Recent Posts