Tomato Flowers Not Setting Fruit? 10 Reasons + What to Do

Are your tomato plants blossoming but failing to set fruits? This can be a frustrating experience, especially after putting in more effort. Many gardeners are experiencing this problem without having knowledge of the causes and what to do. So, why are tomato flowers not setting fruits?

There are various circumstances under which a tomato plant may produce flowers but fail to set fruits. They include extreme temperatures, high or low humidity, insufficient light, inadequate or excess water, heavy flowering, poor pollination, winds, insects, and disease attacks.

Why Tomato flowers are not setting fruit

Environmental factors such as temperature, humidity, wind, and light are major causes for tomato flowers not setting fruits. Poor Management practices in fertilizer application, watering, pest, and disease control can also cause this problem to happen. Let’s have a deeper look at each of them:

1. Extreme temperatures

Too high temperatures during the day and too cold at night can negatively affect the pollen grains and the entire pollination process. Favorable temperature for normal pollination and fruit development ranges from 70 – 80 degrees Fahrenheit (21.1 – 26.7 degrees Celsius).

Temperatures above 85 degrees Fahrenheit during the day and below 55 degrees Fahrenheit at night can make the pollen nonviable. Pollination does not occur when the temperatures are too high or too low, the flowers dry and fall off without developing the fruits.

2. Extreme humidity

The ideal humidity for better pollination in tomatoes ranges between 40 – 70 %. When humidity is too high, it makes it too difficult for the pollen grain to detach from the male part of the flower. The pollen becomes clogged in the anthers.

On the other hand, low humidity makes it difficult for pollen to stick to the female part of the flower known as stigma. Unfortunately, there is much you do to save your tomatoes from extreme humidity.

3. Insufficient light

Tomato plants may also fail to produce fruits due to inadequate light. Tomato plants require at least 6 to 8 hours of direct sunlight per day to stay healthy. Like any other green plant, tomatoes require light in the process of photosynthesis to produce the energy required by the plant for fruit development and other functions.

Inadequate light causes the plant to have a leggy growth with plenty of foliage. It may produce flowers with little or no fruits. Tomato plants require a lot of energy from the sun to grow healthy and produce flowers and fruits.

4. Inadequate or too much water

Poor tomato fruiting also results from incorrect watering. Inadequate or too much watering can cause nutritional imbalances that prevent the plant from setting fruits. Inadequate water causes the plant to become stressed and hence focus the attention on survival rather than fruit production.

Too much water in the soil can also be detrimental to the plant. It may harbor diseases that can attack tomato plants and prevent them from fruiting. 

5. Improper nutrients

Tomato plants require rich and fertile soils to produce flowers and fruits. Imbalanced nutrients in the soil can cause tomato blossoms to fall without forming fruits. Tomato plants are heavy feeders, they require top dressing after every two weeks to produce enough energy.

Excess nitrogen in the soil during the flowering period may be the cause of tomatoes not producing fruits. Nitrogen promotes foliage growth at the expense of flowers and fruit production. The soil is supposed to have an adequate amount of phosphorus, potassium, and magnesium, especially during flowering.

6. Heavy flowering

Too many flowers on the plant can also be a problem. Competition for nutrients among the flowers can cause some to dry and fall off without setting fruits. Tomato plant requires a lot of energy for fruit development. The plant may not have enough energy to support many flowers.

This problem normally resolves on its own after the plant goes through the fruiting process as long as the soil has adequate nutrients. However, you can add organic fertilizer to the soil when in doubt.

7. Insects and diseases

Various insects like thrips, aphids, and hornworms can attack tomato plants and feed on the flowers before they set fruit. On the other hand, tomato plants are prone to various diseases that can cause blossom drop before fruiting.

8. Poor air circulation

Poor air circulation around the plants causes blossoms to drop before setting fruits. Planting tomatoes closer to each other, failing to stake, planting next to a building or structure, and late pruning leads to poor air circulation around the plant. Pollen grains move freely when there is good air circulation.

When air movement around the plant is hindered, the pollen grains cannot move hence making it difficult for fertilization to take place.

9. Excess wind

Excess wind may cause the flowers to dry up, which makes it difficult for the pollen grain to stick to the female part of the flower. This can prevent fertilization from taking place. High wind can also result in tomato flowers falling off the vine or getting physically damaged before they set fruit.

10. Poor pollination

Tomato plants are self-pollinating, this means that they have both male and female parts within the same flower. They pollinate and produce fruits on their own. However, tomatoes need to be pollinated with the help of small birds, bees, beetles, butterflies, and small mammals to dislodge the pollen from the male part and transfer it to the female part for fertilization.

Poor pollination occurs especially when planting tomatoes in a greenhouse without vents to allow in pollinators. Other factors like high or low humidity can also cause poor pollination.

What to do when tomatoes are not setting fruit

More often than not, it is environmental factors that lead to tomato flowers not setting fruits. While it is difficult to control nature, there are various ways to encourage fruit set in tomatoes.

Protect your tomatoes from extreme temperatures

Protect your plants from high temperatures by putting up a shade cloth. It should be able to cover the plants from at least 30% of direct heat from the sun. This can be removed when the temperature drops down below 80 degrees Fahrenheit.

While you wait for the temperatures to cool down, keep the plant well-watered and nourished. A healthy tomato plant can easily conquer high temperatures and start producing again once the temperatures subside.

Increase pollination

When growing tomatoes in polythene tunnels or a greenhouse, it is possible that potential pollinators are not finding their way to the plants. Open the doors and create some vents to allow in bumble bees and other pollinators.

Aiding in the process of pollination artificially by hand or an electric toothbrush is a great idea for getting things going again. Shake the plant gently with your hands to dislodge the pollen from the anthers. Alternatively, you can use an electric toothbrush to mimic the vibrating effects of bumble bees.

Water evenly and deeply

Water your plants evenly and deeply around the base. Tomato plants require adequate water to produce enough energy for flowers and fruiting. It is recommended to use drip irrigation when watering your plants, it ensures the water is distributed evenly and deeply around the plant.

Apply mulch around the plants to conserve soil moisture content. Use dried grass clippings, sawdust, wood shavings, and wheat straws as mulching materials. It also prevents the fruits and leaves from coming in contact with the soil.

Use a balanced fertilizer

Feed your plants with low nitrogen especially if your concern is fruiting. High nitrogen in the soil promotes green growth with little or no flowers and fruits. For a bountiful harvest, use a fertilizer rich in potassium and phosphorus when the plant is near flowering.

 If you are not sure about the type of fertilizer to use, conduct a simple soil test to determine the nutritional content of the soil. Alternatively, you can use organic fertilizer to improve the nutritional value of your soil.

Prune your tomatoes

Prune your indeterminate tomato varieties. Pruning too late is the biggest mistake that many gardeners do. Tomato plants require pruning to produce high-quality fruits. Prune some of the flowers towards the end of the bunch to avoid competition for nutrients.

Removing some extra suckers and lower leaves can also help to improve aeration around the plant. The plant will also be able to focus its energy on flowering and fruit development.

Practice crop rotation         

Crop rotation helps to control the buildup of pests and diseases. While practicing crop rotation, do not plant Nightshade plants such as tomatoes, potatoes, and peppers in the same bed year in and year out. They share the same nutritional requirements and may harbor pests and diseases.

Improve air Circulation

Improved air circulation around the plant helps in aiding the process of pollination. It also prevents the buildup of pests and diseases. To improve air circulation; remove some foliage and extra suckers, do not plant tomatoes too close to each other, trellis your plants, and do not plant adjacent to a tall building or a structure.

Final Thoughts

Growing tomatoes is not hard. However, it can be challenging for first-time gardeners. You may notice tiny yellow flowers but fail to see the fruits. If this happens, try to establish the cause and fix the underlying problem for a great harvest in the future.

References

Understanding Tomato Fruit Set – Integrated Pest Management

Growing Tomatoes in the Home Garden – Oklahoma State University

Blossom Drop and Reduced Fruit Set in Tomato – University of Florida