Like many fruits, cucumber plants produce both male and female flowers. When male flowers pollinate the females, they create the cucumbers many people enjoy eating.
Your cucumbers might only have female flowers because of their plant type. Gynoecious plants produce only female flowers, while monoecious plants can have both male and female flowers. Having only female flowers could also be due to not spacing your cucumber plants correctly.
While there is not much that you can do to change the sex of your cucumber plant’s flowers, you can still have a robust harvest if you plan ahead and understand what kind of cucumber seeds you have.
Factors That Determine The Sex of Cucumber Flowers
Male cucumber flowers are normally bright yellow in color. They usually have five petals with the flower’s stamen in the middle, and they store pollen in a sac known as the anther.
Female flowers look very similar to male flowers. However, instead of being attached to the plant with a thin stalk, the flowers sit on top of the budding fruit and resemble miniature cucumbers. The growing cucumber is attached to a stalk.
Without looking beneath the flowers, it’s difficult to determine the sex. However, once you notice a small cucumber-looking growth under one of them, you can be certain that it is a female flower.
Now that I’ve explained the differences between male and female cucumber flowers, I can explore the reasons you might only have female cucumber flowers:
The cucumber variety that you plant will dictate how your cucumber plant flowers and what types of flowers will emerge when blossoming occurs.
The three types of cucumber plants are:
Each plant type has different numbers of male and female flowers. Below is some more information about these three cucumber plants and how they produce flowers:
Monoecious cucumbers produce both male and female flowers but, because the plant offers optimal growing conditions for male flowers, there are always typically more male than female flowers.
Monoecious cucumbers flower in this manner to give the plant the best chance of reproducing. The male flowers grow rapidly and have enough time to become established before it’s time to pollinate.
This happens later in the plant’s blooming cycle when the female flowers begin to appear. Since they have waited to appear, the male flowers have pollen ready to go when they do.
Gynoecious cucumber plants produce only female flowers, and typically bloom early on in the season. They also tend to yield more fruit than monoecious plants, the reason many gardeners prefer them.
Although gynoecious cucumber plants produce a lot of fruit, the harvest window is short. However, if you harvest them quickly, you should still have time in the growing season to plant something else.
When you purchase cucumber seeds, you’ll usually buy something similar to Burpee Organic Cucumber Seeds (available on Amazon.com). These are organic, non-GMO and monoecious seeds.
However, if you choose a gynoecious cucumber plant, you’ll find two different kinds of seeds in the package. The bulk of them will be gynoecious seeds, but there will also be a few seeds (usually a different color) that will produce male flowers. These need to be planted close to the others so that when the flowers bloom, they can get pollinated.
If you choose to hand-pollinate (more on that in a bit) and not rely on bees and other pollinators to get the job done, you still need to have pollen, which comes from the male flowers.
The third kind of cucumber, parthenocarpic, eschews pollination altogether. These plants come from seeds that produce flowers that don’t need to be male and female, so if you have parthenocarpic cucumbers with only female flowers, it doesn’t really matter because the plants will produce fruit regardless.
Since parthenocarpic cucumber plants don’t need pollination to bear fruit, they make excellent greenhouse or indoor plants. These cucumber plants also produce seedless fruit, which many people prefer.
You can buy parthenocarpic cucumber seeds at many nurseries or online.
Suppose you have cucumbers other than gynoecious ones and find that you have a glut of female flowers. In that case, you can find the likely cause in the plant’s environmental surroundings.
While water and soil conditions usually constitute what we mean when we talk about a plant’s environment, those elements don’t affect the sex of your cucumber plant’s flowers.
Rather, the environmental elements involved here have to do with the spacing of your plants. Several studies have shown that plant spacing directly correlates to the number of flowers of each sex.
If your cucumber plants are too close to each other, you will have more male flowers than females. With monoecious cucumbers, this will manifest as fewer female flowers after the plants have established their male blooms.
Conversely, too much space between your plants can result in more female and fewer male plants.
If you find your monoecious cucumber plants have only female flowers, the issue could be the spacing.
Most gardeners plant cucumber seeds in mounds. There should be about five seeds in each mound, and you should plant them one inch (2.54cm) deep in the soil. There should also be at least three feet (0.91 meters) between each mound but they shouldn’t be more than five feet (1.52 meters) apart.
Once the plants begin sprouting, you’ll want to thin each mound, much the same way you thin Swiss chard. Remove all but two or three plants per mound, and be sure to clip the plants at soil level rather than rip them up by the roots.
Regardless of the cucumbers you have, you may need to employ hand pollination, either because your gynoecious cucumbers aren’t being pollinated enough due to a lack of male flowers, or because pollinators in your area are rare.
This is a very common problem because bees are, by far, the number one pollinators. Without them, we would have very few plant-based foods. Sadly, the bee population is decreasing rapidly and, because of this, there is at least one spot in China where 100% of the fruit trees are hand pollinated due to an absence of bees.
Hand pollination isn’t a complicated process, but there are a few steps involved. Here’s how to hand pollinate your cucumber plants:
- Locate a male flower. Locating a male flower is easy because they don’t have a mini cucumber beneath them.
- Remove the petals. Gently remove the petals, taking care not to disturb or dislodge the delicate stamen.
- With the stamen exposed, you should be able to see pollen sticking to it. This is the substance you need, and it is a yellowy, powdery substance.
- Extract the pollen. You can use your finger to extract the pollen, but skin oils can cause it to stick to you instead of to the female flower. Using a brush (especially one designed for pollination) is the best way. You can buy these online or at garden centers. Alternatively, you could use a small paintbrush.
- Carefully take the pollen-filled brush to the female flower and paint the center. You can do this by touching the brush to the middle of the flower.
- Repeat for all your female flowers. This can be a tedious and time-consuming process but it will be worth it in the end.
You can pollinate more than one flower per brush load of pollen. Keep an eye on how much pollen remains on the brush and refill it from another male flower when it starts running low.
Plants such as tomatoes are self-pollinating but sadly cucumbers are not. For pollination, they need both male and female flowers, and if you discover that your cucumber plants have only female flowers, you may have a small harvest of cucumbers unless you take action.
Ensure that your plants are well-spaced and that, if you have gynoecious cucumber seeds, you have the requisite additional seeds to produce some male flowers. Hand pollination can help improve your cucumber harvest.
You can read my other article on whether cucumber plants can have too many flowers here: Can a Cucumber Plant Have Too Many Flowers?