If you have put a lot of care into growing tomato plants from seedlings, then you know how frustrating it can be to see the flowers fall of the plant as they get older. I have seen this happen myself, and I wondered what causes it, so I did some research on the subject.
So, why are your tomato flowers breaking off the plant? A lack of proper pollination will cause tomato flowers to break off the plant without fruiting. This can occur for several reasons, including a lack of pollinators or extreme levels of temperature and humidity. Too much fruit or an imbalance of nutrients in the soil can also cause flowers to break off the plant.
Let’s go into a little more detail about why the flowers might be breaking off of your tomato plant, along with how you can treat the problem. Then we’ll look at preventative measures you can take to get the best tomato harvest possible.
Lack of Pollination
A lack of proper pollination will eventually cause your tomato flowers to fall off the plant. Tomato plants are self-pollinating, which means that a flower contains both male and female parts.
However, self-pollination does not mean automatic pollination. Tomato plants still need pollinators and correct environmental conditions to pollinate the flowers and produce fruit.
Extreme Temperature or Humidity
Extremes in temperature or humidity can prevent proper pollination, even if pollinators such as bees are present and doing their work.
If daytime temperatures go too far above 85 degrees Fahrenheit, then pollination will be inhibited. The same goes for nighttime temperatures above 75 degrees Fahrenheit. This will eventually lead to the tomato plant dropping the flowers.
Of course, if temperatures get up to 105 degrees Fahrenheit, this can cause immediate dropping of the flowers, as the plant shifts focus from reproduction to survival.
At the other end of the spectrum, cooler temperatures will also prevent pollination. If nighttime temperatures drop below 70 degrees Fahrenheit, then pollination will be inhibited.
If nighttime temperatures drop below 55 degrees Fahrenheit, then the plant may immediately drop its flowers. So, keep an eye on the weather forecast, and use covers to keep your tomato plants warm overnight if necessary!
Extremes in humidity levels can also prevent pollination of tomato plants. If the humidity is too high (the air is sticky), then the male part of the flower will not be able to release its pollen.
If the humidity is too low (the air is dry), then the male part of the flower will release pollen, but it will not stick to the female part of the flower.
Both of these situations will prevent pollination, and can eventually cause the plant to drop its flowers. An ideal humidity range for pollination is 40 to 70% humidity.
Lack of Pollinators
Even if the temperature and humidity levels are spot-on, a lack of pollinators can prevent your tomato flowers from being pollinated. Even self-pollinating flowers on tomato plants need something to “buzz” or vibrate the flowers, which causes the male part to release pollen onto the female part.
Usually, this ends up being some type of bee, although other insects, birds, or even wind can do the job. Unfortunately, bee populations have taken a hit in many areas in recent years.
The use of pesticides will kill or repel the bees, so if you use pesticides in your yard, then consider using other methods to bring the bees back. You might also have to politely ask your neighbors to refrain from using pesticides, especially if they notice a lack of bees.
Planting plenty of flowers near your garden will also help to attract bees to your yard, where they will hopefully pollinate tomatoes and other plants in your garden.
How to Pollinate Your Tomato Plants
Of course, you may not have success in bringing bees back to your yard to pollinate your tomato plants. In that case, you will have to do it yourself.
One popular method is to use an electric toothbrush to “buzz” the back of each flower on the plant. You can also use a tuning fork if you want!
This will simulate the flapping and vibrating of a bee’s wings, and cause the male part of the flower to release its pollen. You will know it is working when you see a puff of pollen released from some of the flowers.
You can also use a toothpick, pencil, stick, or cotton swab to pollinate. Simply use the toothpick to push the flower out of position. Then, let it go, so that it “springs” back into place. The movement will cause a vibration and the male part should release pollen.
As mentioned above, temperature and humidity are factors in pollination, so make sure that you go out to hand-pollinate when the temperature and humidity are right. Again, the weather forecast is your friend!
The best time to pollinate is within a couple of hours of noontime. If the forecast calls for hot and humid weather, go out to pollinate in the morning or evening, when temperatures are cooler.
Too Much Fruit
You may be in the situation where your tomato plants have already been properly pollinated, and some of the flowers are starting to produce fruit. It is possible to have too much of a good thing, and if this is the case, then some of the flowers may start to drop off the plant. Let’s find out why.
Why Too Much Fruit is a Problem
First of all, your tomato plant can only support so much fruit in a season. There is a limit on how much water and nutrition the root system can pull up from the soil to the fruit. There is also a limit on how much sunlight the plant can absorb for photosynthesis.
In short, a tomato plant can only produce so much energy in a season, and this will limit the amount of fruit that it can support to maturity. If too many flowers are pollinated, then the plant will drop some of them off. The reasoning is that twenty perfectly ripe tomatoes are better than forty half-ripened ones.
Water and nutrition are not the only limits for how much fruit a plant can produce. The fruit is held by branches off the main vines of the tomato plants.
If too many fruits on one branch grow large, then the branch can bend or snap, which will cause all of the fruit to be lost. Too much fruit can even cause the whole plant to fall over or snap the stem. To learn more, check out my article on how to support your tomato plants.
In short, if you are losing flowers but have fruit on your plant, then take comfort in the fact that your tomato plant is too successful, and so it needs to slow things down a bit.
How To Solve The Problem Of Tomato Plants Dropping Flowers
If you want to allow your tomato plant to set even more fruit, there is one way to do just that. When you see some of the early flowers blooming, pinch them right off the plant. This will encourage the plant to focus its energy on root and vegetative growth, resulting in a stronger plant.
Stronger stems and branches will be able to support the weight of more tomatoes, and stronger roots will be able to provide the water and nutrition for those tomatoes. It is a short-term sacrifice for a long-term gain.
It is possible that the flowers are falling off of your tomato plant because of a nutrient imbalance. This problem is not as common as lack of pollination or excessive fruit set, but if you think it could be a cause, then read on.
Nitrogen: Too Much of a Good Thing?
Nitrogen is an essential nutrient for plant growth, and it helps plants to green up. That is, nitrogen promotes vegetative growth: vines, shoots, and leaves.
Having plenty of nitrogen in the early stages of growth is a good thing. Having too much nitrogen in later stages can prevent flowering, since the plant continues to focus on vegetative (green) growth. For more information, check out my article on low-nitrogen fertilizers.
Avoid adding heavy nitrogen levels to your garden soil, and make sure to use a balanced fertilizer that also contains phosphorus and potassium. Speaking of which, let’s also discuss those nutrients.
Phosphorus: Necessary for Flowering
Phosphorus is another essential nutrient for plant growth. A lack of phosphorus will prevent flowering, so make sure that your fertilizer contains enough phosphorus.
If add your own compost made from grass, leaves, food scraps, and manure, then you will likely have plenty of phosphorus in your soil.
Potassium: Good for Fruiting
Once your flowers are pollinated and the plant begins to set fruit, it will need plenty of potassium to ensure that the tomatoes are large and ripe at harvest.
Potassium is found in most garden store fertilizers or in a compost mix that you make yourself.
Calcium: A Lack Causes Blossom End Rot
One final note about nutrients: if you have a lack of calcium in your plants, then the fruit will have brown or black spots on the bottom, known as blossom-end rot. This can occur if there is not enough calcium in the soil, or due to uneven watering.
Calcium deficiency can also occur if there is a nutrient imbalance in the soil. For instance, too much magnesium can block the uptake of calcium, so be careful when adding Epsom salts to your soil! For more information, check out my article on calcium deficiency and my article on using Epsom salt for growing tomatoes.
To confirm any nutrient deficiency in your soil, you can send your soil away for a soil test. For more information, check out my article on testing your soil.
Other Causes of Tomato Flowers Breaking Off
There are a couple of other potential issues that may cause the flowers to break off of your tomato plants: disease or pests.
Bacterial or fungal diseases can stress your tomato plants and cause them to drop their flowers. Planting tomatoes in the same part of your garden every year can promote growth of diseases, so be sure to practice crop rotation to prevent this.
Also, when watering your plants, be sure to water close to the ground, not from above. This is especially true if you water in the evening, after work.
If the leaves get wet and stay wet, then they can grow fungus. If you water in the morning, then the daytime heat and the sun will dry out the leaves and soil to prevent fungus growth or root rot.
Black spots on the leaves, stems, or fruit of your tomato plants are a sign of many serious diseases. For more information, check out my article about black spots on tomato plants.
Be sure to water evenly, since uneven watering can cause calcium deficiency and blossom-end rot in your tomato plants – even if there is plenty of calcium in your soil!
Pests such as insects, rodents, or other creatures can put pressure on your tomato plants and cause them to drop their flowers due to stress.
Since pesticides can kill or repel bees, your best bet is to use organic methods to fight pests. For instance, you can release ladybugs into your garden to eat aphids if you see them on your plants. For more information, check out my article on how to get rid of aphids in your garden.
Beneficial nematodes will also act as parasites to many common garden insect pests.
You can also use companion planting to put plants in your garden that will repel pests that normally go after tomatoes. For instance, planting marigolds is thought to protect tomato plants from pests in the soil that go after the roots.
By now, you should have a good idea of what is causing your tomato flowers to break off the plant. Hopefully, you also have an idea of how to treat the problem this year, and how to prevent it in future years.
I hope that this article was helpful. If you have any questions, or any tips that worked well for you, please leave them in the comments below.