The first summer I grew tomatoes on my balcony the plants looked wonderful. Tall, dark green, covered in little yellow flowers. Then the flowers turned brown and dropped, one after another, and by the end of August I had picked exactly four tomatoes. Nothing was wrong with the plants. The problem was that nobody was shaking them.
Out in an open garden, bees and wind take care of that without anyone noticing. Up on a balcony, behind greenhouse glass or in a sheltered corner of a yard, they often do not, and the plant is left holding pollen it cannot use. That is the gap you step into.
Learning to hand pollinate tomato flowers is a one minute job that can change your whole season. It is the difference between a plant that flowers beautifully and drops the lot, and a plant that keeps setting fruit from midsummer until the weather turns. You do not need anything you would have to buy, and you certainly do not need to be a botanist. Knowing what is happening inside the flower does make the whole thing click, though, so that is where we will start.
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What Is Actually Going On Inside a Tomato Flower
Tomato flowers are self fertile, which is a nice piece of luck. Every single flower carries both halves of the job, so you never need a second plant and you never have to move pollen from one flower to another. Everything it needs is already sitting there.
Look closely at an open flower and you will see a small yellow cone hanging in the middle of the petals. That cone is made of the stamens, fused together into a tube, and the pollen is produced on the inside of it. Running down the center of the tube is the style, with a sticky tip called the stigma, and that tip is where the pollen has to land. Above all of it sits the ovary, a tiny green ball that becomes the tomato, packed with ovules that become the seeds.
So the pollen starts out a fraction of an inch from where it needs to be, and there it stays. Something has to knock it loose. In a garden that something is usually a bumblebee, which grips the flower and vibrates its flight muscles at just the right frequency until the pollen showers out. It is called buzz pollination, honeybees cannot do it, and it is the main reason bumblebees are worth their weight in gold around tomatoes. A steady breeze does a rougher version of the same job.
On a balcony, in a greenhouse or on a windowsill, neither of those shows up reliably. The flower opens, waits two or three days for a shake that never comes, and then lets go.
Why Flowers Still Drop in a Heat Wave
Movement is only half the story. Heat is the other half, and it is the reason midsummer can be so maddening.
Tomato pollen is fussy about temperature. Once daytime highs push past 90°F (32°C), or nights stay above 75°F (24°C), the pollen begins to lose viability and no amount of tapping will bring it back. Humidity matters too. Muggy air makes the grains clump together so they will not fall, and very dry air, below roughly 40 percent, dries the stigma out before anything can stick to it.
That is worth knowing before you start, because it tells you when hand pollinating will pay off and when the plant is really just waiting for the weather to break.
The Best Time of Day to Do It
Late morning to early afternoon, roughly 10 a.m. to 2 p.m. The air is warm by then, the pollen is dry, and the flower is at its most receptive.
You will know a flower is ready when the petals have curled all the way back and the yellow cone is standing clear of them. A flower that is still half closed is not there yet, so leave it and come back tomorrow.
Skip it straight after watering, and skip it on a damp overcast morning, because wet pollen clumps and stays exactly where it is. Once a day is plenty while the plant is flowering, and every other day still gets you most of the benefit, since each flower stays receptive for two or three days.
Method 1: Your Finger
This is the one I use when I am walking past with my hands full, which is most of the time.
Take the stem just behind a flower cluster and give it a sharp flick with your fingernail. One good tap is enough. You can also hold the main stem lower down and shake the whole plant for a second or two, which covers every open flower at once. If the sun happens to be behind the plant you will sometimes catch a faint puff of pollen coming off, and it is oddly satisfying every time.
It costs nothing and takes seconds. It is also the least thorough of the four, so on a plant that has been dropping flowers I would reach for something with a bit more precision.
Method 2: A Small Paintbrush
A soft artist’s brush, the sort you would use for fine detail work, is the classic tool for this and it is still my favorite when there are only a few plants to get through.
Slide the tip up into the yellow cone, wiggle it for a second, then move along to the next flower. The bristles pick up loose pollen and carry it down the row, so you are shaking and transferring at the same time. That second part makes a real difference on a plant that has only just started flowering.
One thing worth knowing: if you are saving seed and growing more than one variety, keep a separate brush for each. Otherwise you can end up with crosses you never planned. Let the brush dry out between sessions so pollen does not cake into the bristles.
Method 3: A Cotton Swab
Same idea as the brush, a little gentler, and you almost certainly have a box of them in the bathroom already.
Roll the cotton tip around inside the flower for a second or two, then move on. Cotton holds moisture, so once a swab starts to look damp or grubby, throw it out and start a fresh one rather than dragging it through the rest of the plant.
This is what I would suggest to anyone with two or three plants on a windowsill. It is forgiving, it costs almost nothing, and it will not bruise a thing.
Method 4: An Electric Toothbrush
If you take one thing away from this article, make it this one. An electric toothbrush is the closest thing most of us own to a bumblebee, and on a plant covered in flowers it is far quicker than anything else here.
Switch it on and touch the back of the head against the stem just behind a flower cluster. One or two seconds is enough. The whole truss vibrates and you can actually see the flowers shiver as the pollen comes free.
Touch the stem, not the flower. Bristles pressed straight onto the petals will bruise them and can knock a flower clean off the plant. An old toothbrush retired from bathroom duty is perfect, and a cheap battery powered one works just as well as an expensive model.
How to Tell It Worked
Give it a couple of days. The petals fold back, turn papery and drop away, and behind them you will find a tiny green bead sitting on the stem. Five to seven days after that it is unmistakably a small tomato.
That little bead is the ovary, the same one in the diagram further up, and it starts filling out almost straight away. For the first few days the dried remains of the flower often stay stuck to the tip of it. That is a good sign rather than a problem, and they drop off on their own.
After that it is mostly a matter of time. Within a week or two the fruit takes on the shape of the variety, round or oval, and the skin turns a paler, glossier green. From that point nothing more is asked of you until it starts to color up.
A flower that failed looks quite different. It yellows at the little joint where it meets the stem, and the whole thing drops off cleanly, leaving nothing behind. One or two of those is normal on any plant. If it is happening to most of your flowers, check the thermometer before you start blaming your technique.
When It Is Simply Too Hot
There is a point where the pollen itself is no longer viable and no amount of tapping will change that. When a heat wave settles in, move your round to first thing in the morning, while the pollen still has the cool of the night in it. Throw a shade cloth over the plants for the worst few hours of the afternoon, mulch the pots so the roots stay cooler, and water deeply rather than often.
It is also worth knowing that small fruited varieties cope far better than big ones. Grape and cherry tomatoes will often keep setting fruit right through a spell that stops a beefsteak completely, which is one of the reasons they do so well on a hot balcony.
Once the habit sticks, the whole thing takes about a minute a day and you will find yourself doing it without thinking. The same trick works on peppers and eggplants, so one toothbrush can cover the entire balcony. If your plants are also putting out far more leaves than flowers, pruning them is worth a look, and when you find a variety that keeps producing for you in the heat, save the seeds and grow it again next year.
Frequently Asked Questions
Do tomatoes need bees to produce fruit?
No. Tomato flowers pollinate themselves. Bees and wind only supply the vibration that shakes the pollen loose, and your hand can do exactly the same job.
What time of day should you hand pollinate tomatoes?
Between about 10 a.m. and 2 p.m., when the air is warm and dry and the pollen is at its loosest.
How often should you hand pollinate tomato flowers?
Once a day while the plant is in flower. Every other day still gives good results, because each flower stays receptive for two or three days.
Why are my tomato flowers falling off?
Usually heat or a lack of movement. Pollen loses viability above 90°F (32°C) in the day or 75°F (24°C) at night, and sheltered plants never get the shaking that releases it.
Can you hand pollinate tomatoes with an electric toothbrush?
Yes. Hold the back of the running toothbrush against the stem just behind the flower cluster for a second or two. It mimics the vibration a bumblebee makes.
How long after pollination do tomatoes appear?
A small green fruit is visible behind the spent flower within five to seven days.
