It is frustrating to see your tomato plants flower without producing any fruit. Luckily, there are some steps you can take to identify the problem and save your harvest.
So, why do tomato plants flower but not produce fruit? A lack of pollination due to extreme temperature or humidity will cause tomato plants to flower but not produce fruit. Other environmental factors that delay fruit production include: water, light, or nutrient deficiencies, pests, and diseases.
It’s important to remember that it takes over a month to go from the appearance of a flower to a ripe tomato. So, be patient!
Still … if you aren’t seeing any fruit on your tomato plant and flowers keep dropping off, then it is time to do some detective work and find the source of the problem.
In this article, we’ll start with pollination for tomato plants: how it works, what prevent its, and how to take matters into your own hands.
Let’s begin.
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Tomato Plant Pollination
If your tomato plant has flowers but no fruit, a lack of pollination is the most likely cause. Before we can understand a lack of pollination, we need to know how pollination works for tomato plants.
How Does Tomato Plant Pollination Work?
Tomato plant flowers are self-pollinating. This means that each flower contains both a male part and a female part. (It is a myth that 2 tomato plants are needed to get fruit; one plant will pollinate itself!)
However, self-pollination does not mean guaranteed pollination. Tomato flowers do contain both a male and a female part, but they still need help for pollination to occur.
Usually, a bee provides this help for tomato flowers. When bees visit flowers in search of nectar, they hover near the flower. As their wings vibrate, the bees cause the flower itself to vibrate.
This, in turn, causes the male part of the flower to release pollen onto the female part of the flower. If conditions are right, then the female part of the flower will be pollinated.
The flower will then form fruit, which should develop into a healthy tomato if there is enough water, nutrients, and sunlight.
Obviously, this process does not always work so easily. In fact, according to the University of Maryland Extension: if the flower is not pollinated within 50 hours of forming, it will abort.
Let’s look at some of the factors that can prevent pollination of tomato plant flowers.
What Prevents Tomato Flower Pollination?
There are several factors that can prevent tomato flower pollination, including:
- Lack of pollinators (especially bees)
- Extreme temperature (too hot or too cold – day or night)
- Extreme humidity (too dry or too damp)
(Click on the links above to skip to that section of the article).
We’ll look at each one in turn, starting with pollinators.
Lack Of Pollinators
One big factor that prevents tomato flower pollination is a lack of bees. Bee populations have been declining in many parts of the U.S. and the world in general.
Part of this is due to diseases, and part of it is due to pesticides or other chemicals used in farming and gardening.
If you don’t see many bees in your garden, consider going pesticide-free to give the bees a chance to recover. Planting flowers to attract bees is also a good idea.
(You can learn how to create a pollinator garden to attract bees here).
You can even ask your neighbors to do the same to create a larger area where the bees can live and work. Beekeeping is another option if you also want honey every year!
Extreme Temperature
Another factor that prevents tomato plant pollination is extreme temperature or humidity. Pollination will often fail if daytime temperatures go far above 85 degrees Fahrenheit, or if nighttime temperatures go far below 55 degrees Fahrenheit.
In fact, according to the Penn State University Extension:
“When daytime temperatures exceed 90o degrees several days in a row and nighttime temperatures remain above 72o degrees in the same time period, pollen can become nonviable.”
https://extension.psu.edu/programs/master-gardener/counties/northampton/news/2018/why-are-my-tomato-flowers-drying-up-without-forming-fruit
So, pollination may be delayed during a heat wave in the summer, or during a cold spell in an area with a short growing season.
The tables below provide a summary of how various temperature ranges affect tomato flower pollination.
For nighttime temperatures:
| Temperature Range | Effect on tomato flower pollination |
|---|---|
| Below 55F (below 13C) [nighttime] | Prevents pollination of tomato flowers. |
| 55F to 72F (13C to 22C) [nighttime] | Acceptable range for tomato flower pollination. |
| Above 72F (above 22C) [nighttime] | Prevents pollination of tomato flowers if such temperatures persist for a few days. |
For daytime temperatures:
| Temperature Range | Effect on tomato flower pollination |
|---|---|
| Below 55F (below 13C) [daytime] | Prolonged exposure causes flower drop and other problems. |
| 55F to 70 F (13C to 21C) [daytime] | Below optimal range for tomato flower pollination. |
| 70F to 85F (21C to 29C) [daytime] | Optimal range for tomato flower pollination. |
| Above 85 F (above 29C) [daytime] | Prevents pollination of tomato flowers. |
Extreme Humidity
Even if you get the temperature right, the humidity might still be off. The best relative humidity level for tomato plants is 40% to 70%. Outside of this range, you may see a lack of pollination.
If humidity levels are too high, then the male part of the flower will not be able to release the pollen onto the female part of the flower. If humidity levels are too low, then the pollen released by the male part will not stick to the female part.
Excessive wind can also contribute to tomato flowers drying out. For more information, see this article from the Iowa State University Extension on how temperature and wind can affect tomato flower pollination.
There is not much you can do about the weather conditions to help your plants. Although, a greenhouse that is tall enough can house tomato plants and increase humidity levels if it is too dry.
However, you can certainly try to help with pollination, especially if there are not enough bees to do the job.
How Can I Hand Pollinate My Tomato Flowers?
Maybe the bee population in your garden is not enough to allow for pollination. Or, maybe you want to give your plants an extra chance to pollinate during hot or cold weather.
Either way, here is a step-by-step on how to hand pollinate your tomato flowers.
First, choose your tool for hand pollination. One of the best is an electric toothbrush. The vibration of the toothbrush will simulate the vibration caused by a bee’s wings.
You can also use a tuning fork (strike it against something hard and then use it while it is vibrating).
In addition, you can use a toothpick, pencil, or stick to move the flowers out of place, causing them to vibrate when they spring back to their original position.
Second, choose the time that you will hand pollinate. In the middle of a heat wave, hand pollination works best in the morning or late evening, when temperatures are cooler. This will give the pollen a better chance to work.
If you are getting unseasonably cold weather, then look at the weather forecast and try hand pollination at the warmest time of the day.
(If you are worried about cold damage to your tomato plants, check out my article on how to protect your tomato plants from cold and frost).
The more often you use hand pollination, the better the chance it has of working. Choose pollination timing wisely to increase your chance of success.
Be sure to visit every flower you see. Go around all sides of each tomato plant to make sure you don’t miss any.
For more information, check out my article on hand pollination for tomato plants.
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What Else Causes Tomato Plants To Flower Without Fruit?
Aside from a lack of pollination due to heat or humidity, there are other issues that cause flowers but no fruit on tomato plants, including:
(Click on the links above to skip to that section of the article).
Let’s start with nutrient imbalances.
Nutrient Imbalances
A possible cause of a lack of fruit on flowering tomato plants is a nutrient imbalance. Let’s start with excessive nitrogen.
Excessive Nitrogen
Many gardeners know that nitrogen is a necessary nutrient for plant growth. However, you may not know that too much nitrogen can prevent flowering or fruiting of plants.
Nitrogen is the nutrient that helps plants to produce lush, green foliage. This is helpful when the plant is trying to grow taller and store energy in its roots.
However, the plant must eventually put this energy to use by producing flowers and fruit. When a plant has too much nitrogen, it gets the signal to continue producing green growth (rather than flowers and fruit).
Using manure or a high-nitrogen fertilizer causes excessive nitrogen in your soil. If the nitrogen levels are high enough, you may even see some plants that fail to flower at all.
(For more information, check out my article on over fertilizing plants and my article on low-nitrogen fertilizers).
The solution: be careful when fertilizing your garden. Follow the directions on fertilizer packages, and use a calculator to figure out the correct amount (based on the area to cover, fertilizer type, etc.)
Be sure to provide enough of other nutrients to your plants, such as phosphorus, potassium, calcium, iron, and magnesium.
Often, a good compost mix will provide the nutrients that your tomato plants need to produce fruit. However, there are some cases where you can still experience nutrient deficiencies.
Lack Of Nutrients
A lack of nutrients will prevent tomato plants from producing fruit or even flowers. A nutrient deficiency will often display symptoms such as yellow leaves on a plant.
(For more information, check out my article on nutrient deficiencies in plants).
As an example: potassium is necessary for plants to move water through their tissues. In short: lack of potassium leads to lack of water which leads to yellow leaves (and other problems).
Even if you have plenty of a given nutrient in your soil, your plants can still experience nutrient deficiencies if the soil pH is incorrect.
For each nutrient, there is an ideal pH range where it is most available in the soil. Outside of this ideal pH range, the nutrient becomes less available for plants to absorb through their roots.
(For more information, check out this article from Research Gate on nutrient availability depending on soil pH).
If you suspect that your soil pH is outside of the ideal range (for tomatoes, it is 6.0 to 7.0, or slightly acidic) the best way to find out is to do a soil test.
You can buy a soil test kit online or at a garden center to do it yourself. You can also send a soil sample to your local agricultural extension for more detailed testing.
(For more information, check out my article on soil testing).
Lack Of Sunlight
Remember that tomato plants need 6 to 8 hours of full sunlight every day in order to develop properly. Without sunlight, tomato production will be delayed – or it might never happen at all.
Transplanting mature tomato plants is risky. Unfortunately, all you can do is to choose a sunny spot for planting next year’s crop.
Improper Watering
Too much or too little water will also put stress on your plants. Eventually, it will cause them to drop flowers or prevent fruit from forming.
If you over water your plants, the roots will rot if the soil stays wet for too long. This is more likely when the weather is cool, damp, and calm (no wind).
Eventually, it may look like your tomato plants are drying out. However, the truth is that they do not have enough living roots left to absorb water from the soil.
(For more information, check out my article on over watering your plants).
The best test is to feel the soil with your hands, down to a depth of a few inches. If it feels dry, go ahead and water your plants. Just be sure to avoid watering before a big rainstorm.
If you find that your tomato plants look dry and the soil is always dry, consider a deep watering once in the morning. That way, the water gets a chance to soak into the soil before the sun gets higher and temperatures rise to evaporate the water.
(For more information, check out my article on how to treat dry soil).
Pests
Common garden pests (such as aphids or tomato hornworms) also cause stress to your plants. In severe cases, fruit will fail to develop, or it will drop off. You might even see the flowers dropping off the plant.
In cases of severe aphid infestation, you will have to remove and destroy infected plants to protect the rest.
For more information, check out my article on how to get rid of aphids.
Diseases
There are many tomato diseases to worry about, and they are too numerous to list them all here. The best defense against diseases is to stop them from happening in the first place.
Choose disease-resistant tomato plant varieties. The plant descriptions in a seed catalog will have codes for this. As an example: the code “EB” means “early blight” and “LB” means “late blight” (referring to plants that resist these diseases).
Another tip is to use crop rotation in your garden. This means that you should not plant the same crop in the same place every year.
Rather, get on a 2, 3, or 4 year crop rotation schedule to prevent the chance of diseases and nutrient deficiencies in your soil.
(You can learn which crops to rotate with tomatoes here).
Conclusion
Hopefully, this article gave you an idea of why your tomato plants are flowering without producing fruit, and what you can do about it.
Pollination is the first place to look – if that is the problem, then you have some work ahead of you! Don’t worry though – the payoff of delicious tomatoes is well worth the effort!
You can learn more about why tomatoes flower early in this article.
You might also be interested in reading my article on how long it takes tomato plants to bear fruit (from seed to mature fruit).
Thanks for reading – I hope you found this article helpful. If so, please share it with someone who can use the information.
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~Jonathon