Tomato Flowers But No Fruit: Pollination & Temperature Guide

Illustration of tomato plants in pots with bamboo supports

Affiliate disclosure: As an Amazon Associate I earn from qualifying purchases. This article contains affiliate links.

When tomato plants produce healthy flowers but fail to develop fruit, the cause is typically a failure in pollination or an environmental stressor that prevents the flower from setting. Tomatoes are self-pollinating, meaning a single flower contains both male and female organs. However, the pollen must still be physically moved within the flower to fertilise the ovule. If the air is too still, too humid, or the temperature is outside the plant’s optimal range, the pollen may become sterile or fail to release, leading to ‘blossom drop’ where flowers simply wither and fall off.

Table of Contents

Diagnosing the cause of flower drop

Before applying remedies, it is necessary to distinguish between pollination failure and physiological stress. Pollination issues often manifest as flowers that look healthy for several days but then yellow and drop without any fruit forming at the base. In contrast, physiological stress may be accompanied by other symptoms:

Temperature stress: If the plant is struggling with extreme heat or cold, you may notice curling leaves or stunted growth alongside the lack of fruit.
Viral infection: Certain viruses, such as Tobacco Mosaic Virus (TMV), can cause a condition known as ‘dry set’, where fruit specifically fails to set despite the presence of flowers. This is often accompanied by mosaic patterns of lighter green on the leaves.
Nutrient imbalance: While less common as a primary cause of flower drop, severe deficiencies can weaken the plant’s overall reproductive capacity.

Temperature checks for fruit set

Tomatoes are highly sensitive to temperature fluctuations. If conditions are too extreme, the plant may abort its flowers to conserve energy or because the pollen has become non-viable.

Minimum temperature thresholds

Tomatoes generally will not thrive if temperatures drop below 12°C. In early summer, cold nights can cause the plant to struggle with carbohydrate accumulation, which may lead to leaf curling and a failure of flowers to set fruit. For outdoor plants, using fleece can provide a small degree of protection against these dips.

Maximum temperature and humidity

Excessive heat in a greenhouse can be just as detrimental as cold. High temperatures combined with high humidity can make pollen ‘sticky’, preventing it from falling onto the stigma. Conversely, very low humidity can dry out the stigma, making it impossible for pollen to germinate. Monitoring temperature with a maximum-minimum thermometer and humidity with a hygrometer is the most effective way to identify if your greenhouse is hitting these critical extremes.

Improving pollination in greenhouses

Because greenhouses are sheltered environments, they often lack the natural wind and insect activity required to shake pollen loose within the tomato flower. To resolve this, you can employ several manual techniques:

Ventilation: Open vents and doors regularly. This not only regulates temperature but allows pollinating insects to enter the growing area.
Mechanical vibration: Lightly tap or shake the flower trusses when the flowers are fully open. This mimics the vibration caused by wind or bees, helping the pollen transfer within the flower.
Misting: Lightly misting the flowers with water can sometimes assist in the pollination process by adjusting the immediate micro-environment around the bloom.

Managing environmental stressors

Beyond pollination, the overall health of the plant determines whether a pollinated flower successfully develops into a fruit. Fluctuating conditions can lead to physiological disorders.

Watering consistency

Erratic watering—alternating between bone-dry soil and flooding—stresses the plant. This instability can contribute to flower drop and, later in the season, cause fruit splitting or blossom end rot. To maintain steady moisture, consider sinking a 15cm pot into the ground next to the plant and watering directly into it; check that this wets the surrounding root zone; a watering pot cannot guarantee prevention of stem rot.

Airflow and humidity

Excessive atmospheric humidity can lead to oedema, where lumps and nodules appear on the foliage because the plant cannot transpire water quickly enough. While oedema primarily affects leaves, the same high-humidity conditions that cause it often hinder the release of pollen from the anthers.

Distinguishing between Cordon and Bush needs

While pollination needs are the same for all tomatoes, the way you manage the plant to support fruiting differs by type:

Cordon (Indeterminate): These vigorous plants require the removal of side-shoots. If side-shoots are left to grow, the plant may divert too much energy into foliage and ‘scrambling’ stems, potentially reducing the energy available for fruit set on the main stem.
Bush (Determinate): These are more compact and do not require side-shoot removal. Their primary risk is physical; if they produce a heavy crop, the stems may droop, which can occasionally lead to flower clusters being pressed against the ground or supports, hindering pollination.

Next step for the gardener

Begin by installing a maximum-minimum thermometer in your growing area to track temperature swings over a 48-hour period, and implement a daily routine of gently shaking your flower trusses to help pollen transfer when flowers are fully open; it cannot overcome all temperature or plant-health problems.

Useful products for this job

The links below open Amazon UK product searches. Check the exact item, seller, current price and compatibility before buying.

Maximum-minimum thermometer: Essential for tracking the temperature fluctuations that cause pollen sterility and flower drop. Ensure it has a clear record of the highest and lowest temperatures reached over a 24-hour period. Search Amazon for Maximum-minimum thermometer.
Horticultural fleece: Used to protect outdoor tomato plants from cold night temperatures that inhibit fruit set. Check the GSM (weight) to ensure it provides the desired level of frost and cold protection. Search Amazon for Horticultural fleece.

Related garden guides

Sources and further guidance

Guidance researched in September 2026. The feature image is an AI-generated illustration. Product guidance is based on published information, not hands-on testing.