Flowers but No Fruit? Try Hand Pollination.

Do your fruit-bearing plants produce lots of beautiful flowers but little or no, eh, fruit? This is one of the most common (and most frustrating) problems that plagues gardeners today, especially in urban environments. It’s also often misdiagnosed.

So what gives?

The culprit is pollination—or rather the lack thereof due to declining pollinator populations.  Did you know about 1/3 of our food is a direct result of pollination, which is mostly achieved by honey bees? That’s right. I’m talking about those small, striped, stinging arthropods that sent you swollen and screaming when you got a little too curious about their hive as a child. (No? Just me?)

Yes, it turns out bees are actually our friends. But in the last 70 years, we’ve lost 3.5 million honey bee colonies. Not good.

Attributed to parasites, disease, pesticide exposure and other factors—the decline in pollinator populations has become a serious problem. How serious? Well, President Obama created a “Pollinator Health Task Force.” And some of the most brilliant minds are exploring the idea of artificial bees.

No, seriously. Scientists at Harvard and Northeastern University are building “robobees” to help with crop pollination (and then world domination?!).

But until these penny-sized robotic pollinators hit the market, you may need to resort to hand pollination, also known as manual or mechanical pollination.  

Tower Tip: Hand pollination is pretty easy, but it’s always nice to have help. Consider growing flowers to attract honey bees and other pollinators.

Do You Need to Hand Pollinate?

You should probably hand pollinate if:

• You don’t see bees or other insects hovering around your flowering plants
• You’re growing indoors, in a greenhouse or on a screened-in porch
• Your plants produce fruit that shrivels and dies before maturing

Even with healthy pollinator activity, you may consider hand pollinating simply to prevent cross-pollination between similar plants. This is important if you want to save seeds from your garden to grow more of the same plant—a common practice for heirloom varieties.

Tower Tip: Learn more about the differences between heirlooms and hybrids in this post about seeds.

Top Techniques for Hand Pollination

When it comes to pollination, there are two types of plants: those with self-fertile flowers and those with separate male and female flowers. Watch the following video (or read below) to learn how to hand pollinate each type.

Watch: How to hand pollinate.

How to Pollinate Self-Fertile Plants
Self-fertile (sometimes called “self-pollinating” or “self-fruitful”) plants include:

• Beans
• Eggplants
• Peas
• Peppers
• Strawberries
• Tomatoes

Use a small paintbrush to stimulate pollen release for self-fertile plants like tomatoes.

The flowers of these plants have all the necessary parts to produce fruit. So hand pollination is not usually necessary if you’re growing outdoors, as even a slight gust of wind can often facilitate pollination. But for good measure, here are two ways you can pollinate a self-fertile plant:

• Carefully shake the plant or blow on its flowers to stimulate pollen release; or
• Gently swab the inside of each flower with a small paintbrush or cotton swab to transfer pollen into the pistil (middle part of the flower).

How to Pollinate Plants with Separate Male and Female Flowers
Plants that produce separate male and female flowers on the same plant include

• Cantaloupes
• Cucumbers
• Pumpkins
• Squash
• Watermelons
• Zucchini

In order for these plants to produce fruit, pollen from a male flower must make its way to a female flower. So naturally, these crops tend to struggle with pollination more than self-fertile plants.

Typically, male flowers (which have slender stalks and pollen-laden stamens) bloom first. These fall off a few days after blooming. After a couple weeks, you should start to see female flowers (which usually have small budding fruits at the base).

Cucurbit plants like squash, cucumbers and others produce separate male and female flowers.

It’s easiest to pollinate early in the morning when the blooms are open, using the following techniques:

• Swab the inside of the male flower with a small paintbrush or cotton swab, and then swab the inside of the female flower to transfer the pollen; or
• Pick a male bloom, peel off its petals, and lightly dust pollen onto the pistils of the females with the male stamen.

Next Steps

For best results, you should hand pollinate every few days or until you begin to see fruit. If you don’t see fruit after a week or so, the problem may actually be something else, such as a lack of light or extreme temperatures.

Otherwise, that’s really all there is to it! If you have any questions, please leave me a comment, and I’ll do my best to help.

Happy growing!