As a tomato grower, seeing bright yellow flowers on your tomato plant is almost as exciting as harvesting ripe tomatoes you’ve grown yourself. Tomato flowers are a sign that you will soon have baby tomatoes. This makes seeing your tomato flowers drop before they set fruit devastating. Unfortunately, this is quite common but can be controlled to a certain extent.
What causes tomato flowers to fall off?
- A lack of pollination
Each tomato flower contains both male and female parts and is self-fertilized. Fertilization occurs when pollen moves from the anther at the base of the flower to the tip (stigma) of the same flower. This means that they don’t have to depend on insect pollinators for fertilization.
However, vibration is needed for the flower to release pollen. The vibration produced by bees as they rapidly move their wings, known as sonication, or wind can naturally cause the pollen to be released and flowers fertilized. If pollination does not happen, the flowers will drop within about two days.
- Temperatures that are too high or too low
Despite their tropical origin, most varieties of tomato have quite a narrow temperature range within which they can produce fruit. Temperatures within the range of 65-80° F (18.5 – 26.5°C) are optimum for fruit set. If temperatures are too high or too low, the pollen will lose its ability to function properly and pollination cannot take place.
- Humidity levels that are too high or too low
If you have made sure that the temperature is within the optimum range, you will still need to make sure that humidity levels are also optimal. Relative humidity levels of 40-70% are needed for pollination to take place. If humidity is too low, the pollen will become too dry to stick to the stigma and pollination will not take place. If humidity is too high pollen won’t be able to move to the stigma, again pollination will not take place.
- Inconsistent watering
Tomato plants need a constant supply of water but won’t do well if their root zone remains too wet for an extended period of time. Too much water or too little water will disrupt growth and can cause tomato flowers to drop.
- Too much or too little nitrogen
Although all plants must have enough nitrogen to properly grow and develop leaves, too much or too little nitrogen can be harmful, especially for fruit-set.
If the plant is getting more nitrogen than it needs, it will start to use this additional nitrogen for leaf growth rather than spending energy growing fruits. If the plant does not have an adequate supply of nitrogen, it may not be able to function properly and will stop fruit growth and drop its flowers to conserve energy.
- Tomato plant diseases
When tomato plants are affected by diseases, they may need to stop spending energy on growing fruit and instead direct all the energy they have to fight against the disease. One of the ways that they achieve this is by dropping their flowers.
- Too many flowers
Sometimes tomato flowers may fall off just because the plant is not able to support the number of flowers that have started to grow. If there are enough flowers that are properly setting fruit despite some flowers falling off, there may be no reason to worry. This is just the plant making sure that it can support all remaining fruits as they start to grow and require more energy.
Although there are many causes that result in tomato flowers falling off, all causes lead to or result from either a lack of pollination or because the plant needs to conserve energy, abort fruit production, and concentrate on survival instead.
How to prevent tomato flowers from falling off?
- Mechanically pollinate flowers
A lack of pollination of tomato flowers is quite unlikely when tomatoes are grown directly on the ground or in raised beds. However, if tomato plants are grown in containers in areas where they are not exposed to much wind and are not visited by bees or other pollinators, the flowers will not get pollinated.
If you suspect that this is the case, you can simply tap on the stem nearest to the flower or gently but vigorously shake the plant, once a day after tomato flowers have appeared.
- Grow varieties that are suitable for your climate
As a home gardener, you cannot control changes in temperature and humidity. What you can do is to find out which varieties of tomato are best suited for your climate and grow those varieties.
- Deep and regular watering
Tomato plants can grow roots that can go down up to 5 meters below the ground. Deeply watering your tomato plants once or twice a week or so will allow your plants to develop strong roots that always have access to water if needed. However, if the weather becomes very hot, you may need to water your tomatoes more frequently.
If you grow tomatoes in containers, watering them once a week will not be enough. You will have to water them at least once a day or twice a day if needed. Watering must be regular so that your plants have continued access to water.
Properly watering your plants will also help your plant absorb enough nutrients. You can also mulch your plants to make watering more effective.
- Adding compost
Matured compost is neutral and slowly releases nutrients into the soil or substrate. Adding compost to provide your plants with the nutrients they need is an easy way of making sure that your plants don’t suffer from any nutrient deficiencies or excess nutrients, including nitrogen.
You can mix compost into the soil or substrate before planting your plants in it. You can add more compost when your tomato plants start to produce flowers.
- Prevent and control pest and disease problems
When tomato plants are affected by pests and disease, their priority is survival. Preventing pests and diseases as much as possible will stop plants from getting into this dire situation and allow mature plants to keep producing fruits.
Providing your tomato plants with the best soil and growing conditions early on and continuously observing and treating any problems as they arise is the best way to prevent and control pests and diseases.
Sometimes your tomato plant may have to drop all of its flowers to survive, while at other times dropping some of its flowers may be the best way of allowing the remaining flowers to properly develop into healthy tomatoes.
You can’t control environmental conditions, such as temperature and humidity, which lead to tomato flowers falling off but you can grow the most suitable varieties, provide mechanical pollination if needed, and provide the best plant care possible by following proper watering, fertilizing, and pest and disease control practices to reduce flower drop as much as possible.
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