From pumpkin pie to jack-o’-lanterns, there’s no shortage of uses for this pretty winter squash. Pumpkins are a part of the genus Cucurbita, a group of plants that grows on vines and produces male and female flowers.
The males carry the pollen, while the females carry the fruit to be pollinated. Without the female flowers, there are no pumpkins. Knowing how to promote female flowers on a pumpkin will help improve your pumpkin yield.
Temperature, fertilizer, and water are the three factors that affect female flower growth. To encourage more female flowers on pumpkins, be sure to shade your pumpkins from extreme heat, use a fertilizer high in phosphorus and low in nitrogen, and avoid overwatering by planting pumpkins in raised, well-draining soil.
Let’s look into the best ways to encourage more female flowers, and get you on the right track to a successful pumpkin harvest!
Why is My Pumpkin Not Producing Female Flowers?
A lack of female flowers is certainly concerning. Keep in mind that pumpkin vines produce male flowers earlier than female flowers. Generally, pumpkin seeds germinate after about ten days. The male flowers begin to grow 50-55 days after germination. Female flowers will begin to grow about 10-14 days after the males.
It’s also important to mention that males will always outnumber females. Usually, the ratio is 10 males for every 1 female flower.
Issues with your plant will prevent the female flowers from growing after the males. If you started your pumpkin patch too late in the season, the daytime temperatures may be too hot for the females. Female flowers prefer cooler temperatures than males, and won’t grow in high heat.
A fertilizer too high in nitrogen and too low in phosphorus will also discourage flowering. Waterlogged soil will similarly discourage flower growth due to plant stress and nutrient loss.
How To Produce More Female Pumpkin Flowers
Now that we know the main issues affecting female flower growth, let’s look at how to remedy them!
Shade Your Pumpkin Plant
One thing that you can’t control in outdoor gardens is the weather. If the weather is unseasonably hot and humid, this can delay the production of female flowers.
Pumpkins do like a good amount of sunshine, but become stressed under conditions like heat waves. If temperatures in the day remain above 90°F (32°C) with no reprieve at night, the plant begins to use its energy to survive rather than produce flowers.
Wilting leaves and brown spots are signs that your plant is overheating. If you notice these symptoms, you need to provide your pumpkin patch with some form of shade. A shade cloth is the easiest and fastest way to protect your pumpkins from the heat. You can also use an umbrella, or plant sunflowers nearby for natural shade protection.
Choose the Right Fertilizer
Not all fertilizers are the same. A fertilizer with the correct ratio of nitrogen, phosphorus, and potassium is essential to male and female flower production. Here’s a breakdown of what each of these nutrients does:
- Nitrogen: Helps plants produce more stems and leaves. Also helps make plants greener.
- Phosphorus: Essential for forming roots, flowers, and fruit.
- Potassium: Helps plants grow faster, and stronger.
Many basic fertilizers have an even ratio of nitrogen, phosphorus, and potassium. They’re advertised as 10-10-10, (or 20-20-20) fertilizers. This means they have 10 percent nitrogen, 10 percent phosphorus, and 10 percent potassium.
Pumpkins are fast-growing vines, so excess nitrogen encourages the plant to grow more stems and leaves instead of flowers. What you want is a fertilizer that’s high in phosphorus to encourage flower growth. A good fertilizer ratio for pumpkin plants is 5-15-15. That’s 5 percent nitrogen, 15 percent phosphorus, and 15 percent potassium.
Proper Water Management
Water is the source of life for plants. It delivers nutrients from the soil to the roots to help the plant grow. If there are any issues with watering, your plant will struggle to produce growth.
Pumpkins require a good, deep soak about once a week. If there’s drought, increase this amount. If there’s plenty of rainfall, you can decrease it. Pumpkin vines will often droop in the afternoon sun but perk back up when the weather is shady and cool. This can trick gardeners into thinking their pumpkins need more water. A common result is waterlogged soil and root rot.
Root rot puts a lot of stress on your plant, as it can no longer get the nutrients it needs. The result is wilting leaves and dropped flowers. Flower production may even cease completely.
You can plant pumpkin seeds on a raised mound to prevent flooding in your garden. If the issue is heavy, waterlogged soil, consider raking compost or sand into the soil to increase drainage.
How To Tell If Female Pumpkin Flower is Pollinated
Pollination in pumpkins requires a male and a female flower. Pollination can be carried out by humans, or by pollinators like bees and other insects. For pollination to occur, the pollen from the male flower’s stamen must be transferred over to the female flower. The female flower is the only one that can produce fruit, so if this process doesn’t occur, there won’t be any pumpkins.
The female flower is quite easy to tell apart from the male. The female has a bulbous ovary located behind the flower, while the male does not. Right after pollination, the ovary will begin to swell, and the fruit will start to develop. Keep revisiting the female flowers daily, and if the ovary is growing bigger, this means that pollination was successful and a pumpkin is growing!
Should You Cut Off Male Pumpkin Flowers?
If you’re struggling to grow female flowers, picking off the males unfortunately won’t help. The male flowers naturally grow in greater quantities than the females. This is to ensure there is enough pollen to successfully pollinate the female fruit.
The pumpkin flowers actually self-regulate. Each bloom only opens for about four hours a day. The male blooms will naturally die off at the end of each day to make way for new growth. If the female flower isn’t pollinated, it too will die off.
How Do You Increase the Yield of a Pumpkin?
Factors like temperature, weeds, water, and fertilization all affect the yield of your pumpkin plant. But the most important factor in any garden is good soil.
For the best pumpkin yield, ensure your pumpkins are planted in well-draining soil. A good sandy, loamy soil mixed with compost will give your plant excellent drainage and nutrition at the same time. Pumpkins also prefer a soil pH of 6.0-6.5, so run regular soil tests to ensure you’re in this range.
How Do You Self Pollinate a Pumpkin?
Pumpkins unfortunately cannot self-pollinate. In self-pollinating plants, the male and female reproductive parts are located in the same flower. With a little wind, the pollen from the male anthers can transfer to the female stigma. No need for bees, or humans!
Pumpkin plants have male and female reproductive organs located on separate flowers. So, pumpkins need an extra hand with pollination. In outdoor gardens, natural pollinators like bees will do the job by carrying pollen dust from one flower to another. But sometimes conditions like wind and cold temperatures can deter bees. In this case, you’ll need to do the job yourself by hand pollinating.
To hand pollinate your pumpkin plant, locate the male flower and its pollen covered stamen. Use a paintbrush or a cotton swab to collect the pollen. Then, transfer the pollen to the female pistil. Delicately rub the pollen all around the inside of the flower to make sure it transfers properly.
Do I Need to Thin Out Pumpkin Plants?
Since pumpkins are such fast growers and like to spread, they require lots of space. Pumpkins often become overcrowded if they haven’t been spaced out properly. This prevents the plants from receiving adequate sunlight. The key to avoiding this is to space your pumpkin seeds about 6 ft (1.8 m) apart.
If you’ve skipped this step and are dealing with an overgrowth of pumpkin vines, you can still thin them out. Pumpkin plants have a main stem, from which secondary vines grow. To not stunt your pumpkin plant’s growth, you should only trim secondary vines once they reach 10-12 ft (3-3.5 m). Tertiary vines are the vines that grow off the secondary vines. They should always be pruned because they rarely produce fruit and are a waste of the plant’s energy.
Even if you don’t have the greenest thumb, pumpkins are a great crop for first-time gardeners. They grow quickly and require very little help along the way.
But if the growing conditions aren’t optimal, your pumpkin plant will not produce female flowers. Temperature, fertilizer, and water are the three factors that often affect female flower growth.
Since female flowers prefer cooler temperatures than males, ensure your pumpkins receive shade in extreme heat. Use a fertilizer that is lower in nitrogen and higher in phosphorus to encourage flower growth. Proper watering is also essential to ensure your pumpkin plant gets the nutrients it needs to bloom.