Hand-pollinating flowers on your tomatoes or squash might seem extreme, but there are several reasons why you might wish to take pollination into your own hands. We'll talk about which plants gardeners choose to hand pollinate and what they're trying to achieve—besides a good excuse to be out in the garden and make buzzing sounds. Do you have a yellow and black striped shirt?

Basics of Pollination

We all know that bees (and many other insects, birds, and even mammals) pollinate flowers and that pollination is needed for fruit and seed formation. Unlike a chicken, which will lay a full-sized egg without a rooster around, your tomatoes, peppers, and pumpkins need to be pollinated to make a fruit. 

For pollination purposes, we can divide plants into those with perfect flowers and those with imperfect flowers. Plants with perfect flowers have male and female parts in the same flower—the pollen and the pollen receptors are in the same bloom. Tomatoes, peppers, eggplants, okra and beans fit in this category.

Other plants have imperfect flowers, meaning the male and female parts are on separate blooms. Often, we call them male and female flowers. Cucurbits, which include pumpkins, squash, gourds, cucumbers, zucchini, other summer squashes, and melons, all have imperfect flowers.

Remember drawing or labeling the parts of a flower in grade school science class? Most of us forgot precisely how it works after the test, so here's a quick refresher.

• The female reproductive part of a flower is the pistil, which has three pieces: the stigma, the style, and the ovary. It's the stigma, which catches pollen, that we're concerned with here. 
• The male reproductive part of the flower is the stamen, which has two parts: the anther and the filament. The anther has the pollen we're looking for, and the filament holds it up in the air. 

Pollen from the anther must reach the stigma and travel down the style to the ovary, where its genetic material combines with the genes in the ovules (inside the ovary) to complete the pollination process. Once pollination has been achieved, the plant will start making the fruit, assisting the seeds in their journey to become new plants. That fruit, be it tomato, cucumber, or squash, is what we’re after.

In a perfect situation, our pollinators—bees, wasps, flies, moths, hummingbirds, and more—bounce happily around all day doing their thing, and pollination is done with no effort on our part. Perhaps we encourage pollinators by planting habitats and native species to nurture and feed them, keeping them happy so they stick around. 

Reasons for Hand Pollination

Adequate pollination isn't guaranteed. Gardeners in urban settings may be short on pollinating insects. Isolated plants, like a couple of tomato plants on a third-floor balcony, might not receive much attention. 

Gardeners choose to hand pollinate for many reasons, including:

• When natural pollinators are scarce.
• They have indoor or isolated plants that pollinators may not get to, like indoor tomatoes.
• Specific breeding goals like creating hybrids or breeding new varieties by cross-pollinating.
• To ensure pure seed for seed saving. Pumpkins, squash, and gourds will cross-pollinate, possibly yielding a squmpkin or goursh.

How to Hand Pollinate

While hand pollinating can be as simple as pretending to be a bee with a cotton swab, it can be a bit more involved when trying to maintain purity for seed-saving purposes.

Plants with perfect flowers, like tomatoes, peppers, eggplants, okra, and even beans, can be given a pollinating assist by merely shaking (gently) the flowers. Since both male and female reproductive parts are on the same flower, a little disturbance can be all that's needed to help things along. If you desire, the paintbrush or swab can still be used to stir things up a bit. 

For plants with imperfect flowers, you'll need to identify male and female flowers. The quick tell is to look at the base of the flower. Female flowers will have a little immature fruit that looks similar to the final crop attached just below the petals, between the stem and the flower. Look at a cucumber vine and find a flower with a half-inch-long baby cucumber under the bloom. The same works for other cucurbits—a female pumpkin flower will have a little dime-sized green pumpkinlet under the bloom. The male flowers will have a straight stem right into the bloom.

If your only goal is to help pollination and you aren't concerned about maintaining pure seed stock, then the paintbrush technique works well.

Paintbrush Technique:

• Use a small artist's paintbrush—a round one works well. The cheap ones are just fine.
• Gently rub the paintbrush around on several male flowers, gathering pollen on the brush from the anthers.
• Deposit the paintbrush pollen on the stigmas of the female flowers by bumping and lightly brushing into them, just as a bee might do while it wiggles and crawls around in the flower. Make a buzzing noise if you like! 
• Make sure to keep visiting male and female flowers, allowing the pollen from many flowers or even different plants of the same crop to mingle on your brush or swab. A bee doesn't keep it all straight, and neither should you. Bounce around and flit from flower to flower, but make sure to get pollen on each stigma in the flower for best results.

No Tools Technique

• You can use the same bee-imitation method as above, but instead of a paintbrush, you'll use the actual anther on the male flower.
• Find several male flowers and pluck them. 
• Peel off the petals, but leave the anthers and filaments in place. You'll have the stem and flower base, with an anther sticking up and no petals.
• Use the anther just like a paintbrush or swab, bumping and rubbing it on the stigma to transfer pollen to each one. Remember to "visit" each female flower with the anthers from several male flowers and to brush each stigma in the flower.

Clothespin and Bag Method

If you’re attempting to prevent cross-pollination and preserve true varieties, you'll need to take a few extra precautions. Several good videos are available online to help you, but the gist is:

• Identify male flowers that are about to open. They'll be just starting to show a yellow color at the tips. Use a clothespin at the tip to hold them shut so they don't open.
• Find the female flowers that are about to open the same way and pin them shut as well.
• In the morning, remove the male flowers and peel the petals back, as in the no-tools technique above. 
• Pry open the female flowers and pollinate directly with the anthers of at least two male flowers.
• Encase the now-pollinated female flower with a pollination bag, sometimes called an organza bag (buy them online or at craft stores), and seal it shut to prevent bees or other insects from further pollinating this flower.
• You'll remove the bag in a few days, so mark the base of each female flower stem you pollinated with a loose zip tie or brightly colored string. At season’s end, you’ll be able to identify which fruits resulted from your efforts and only save seeds from them. 

When to Hand Pollinate Flowers

Although temperature, humidity, and other weather factors can affect the viability of pollen, for home gardeners we can just remember to do our bee-imitations in the morning. The pollen is most viable then, and many flowers like squash and pumpkin close up in the afternoon.

Unless you are hand pollinating with the bag technique for seed saving, it's perfectly fine to wait until the flowers have opened to begin hand pollination. Revisit the plant every day or two and repeat as new flowers open. For a tomato in a pot on a balcony, it can be as simple as leaving the paintbrush stuck handle down in the pot and giving all the open flowers a little swish every day before you head to work.