10 Reasons Tomato Flowers Are Not Setting Fruit (And What to Do)

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

Tomato plants may produce flowers but fail to set fruit due to extreme temperatures, high or low humidity, insufficient light, inadequate or excessive water, heavy flowering, poor pollination, strong winds, insects, and diseases.

Why Are Tomato Flowers Not Setting Fruit

Environmental factors and poor management practices are to blame for this problem. Let’s have a deeper look at each element:

1. Extreme Temperatures

Too high temperatures during the day and too cold temperatures at night can negatively affect the pollen grains and the entire pollination process. Favorable temperatures for normal pollination and fruit development should range between 70  and 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. Incorrect Humidity levels

The ideal humidity for better pollination in tomatoes ranges between 40 – 70 %. When humidity is too high, it makes it too difficult for pollen grains 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 on the female part of the flower, known as the stigma. 

3. Insufficient Light

Tomato plants may also fail to produce fruit 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 energy required by the plant for fruit development and other functions. 

Inadequate light causes the plant to have leggy growth. The plant may produce flowers with little or no fruit. 

4. Inadequate or Too Much Water

Poor tomato fruiting also results from incorrect watering. Inadequate water causes the plant to become stressed and hence focusing the attention on survival rather than fruit production. On the other hand, too much water in the soil can cause root rot and other diseases that affect the plant.

5. Poor Nutrition

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

Excess nitrogen in the soil during the flowering period may be the cause for tomatoes not producing fruit. 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 fruit. Tomato plants require 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. Adding some organic fertilizer to the soil can also help boost soil nutrition.

7. Insects and Diseases

Various insects like thrips, aphids, and hornworms can attack tomato plants and feed on the flowers before they set fruit. Generally, tomato plants are prone to various diseases that can cause blossom drop before fruiting, including blight, septoria leaf drop, and many others.

8. Poor Air Circulation

Poor air circulation around the plants causes blossom drop before setting fruit. Planting tomatoes closer to each other, failing to stake, planting next to a building or structure, and late pruning lead 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, and hence making it difficult for fertilization to take place.

9. Excess Wind

Excess wind may cause the flowers to dry up, making it difficult for the pollen grain to stick on the female part of the flower. This can prevent fertilization from taking place. Excessive wind can also physically damage the flowers before they set fruit.

10. Poor Pollination

Tomato plants are self-pollinating, which means that they have both male and female parts within the same flower. They pollinate and produce fruits on their own. However, they need some help from 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. 

What to Do to Help Tomato Flowers Set Fruits

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

1. 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 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 return to the optimum levels.

2. Increase Pollination

When growing tomatoes in polythene tunnels or in 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 by hand is a great idea of getting things going again. Shake the plant gently with your hands to literally dislodge the pollen from the anthers. Alternatively, you can use an electric toothbrush to mimic the vibrating effects of bumble bees.

3. 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, as it ensures the water is distributed evenly and deeply around the plant.

In hot weather, apply mulch around the plants to conserve soil moisture. Use dried grass clippings, sawdust, wood shavings, and wheat straws. The mulch also prevents the fruits and leaves from becoming in contact with the soil.

4. Apply 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.

To get fertilization right, always conduct soil tests to determine the nutritional content of the soil. Alternatively, you can use organic fertilizer to improve the nutritional value of your soil.

5. Prune your Tomatoes

Prune your indeterminate tomato varieties. Pruning too late is the biggest mistake that many gardeners make. Tomato plants require pruning in order 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.

6. Practice Crop Rotation

Crop rotation helps to control pests and diseases. While practicing crop rotation, avoid nightshade plants such as tomatoes, potatoes, and peppers in the same bed year in year out. They share the same nutritional requirements and may harbor pests and diseases.

7. Improve Air Circulation

Improving air circulation around the plant helps in aiding the process of pollination. It also prevents the emergence of pests and diseases. 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 difficult, but it can be challenging for first-time gardeners. You may notice tiny yellow flowers, and some excitement sets in, so you wait for the first fruit to appear, but all in vain. Now you know that tomatoes can fail to set fruit due to unfavorable climate conditions and poor management.