There are few things in the garden that cause as much dread in the gardener as their tomato flowers falling off. One day, the plants are blooming like crazy, and the next, the flowers are shriveled up, laying on the ground next to your plant. You wonder what you did wrong and how to stop it from happening again. Rest assured, there are reasons why tomato flowers sometimes drop from plants and there are ways to prevent it from happening. In this article, I share 6 reasons for tomato blossom drop and offer practical solutions.
Should you be concerned when you see tomato flowers falling off?
Fewer tomato flowers mean fewer fruits, so your initial reaction to flower drop is naturally going to be concern, disappointment, and perhaps panic. A few flowers dropping from time to time is natural (as you’ll learn below), but if you find a significant number of your tomato flowers falling off, you might need to take action.
As with all things in the garden, there are things within our control (watering, fertilizing, etc) and things that aren’t (humidity, temperature, etc). As you learn about the 6 reasons for tomato blossom drop below, you’ll see that some of them are within your control while others are not. Focus on the “why,” and if it’s within your control to remedy the situation, your worry will disappear knowing that the problem is fixable. But, if the “why” is outside of your control, know that it is likely a temporary situation and, with proper action, you can still harvest plenty of tomatoes. Read on to learn more.
What to do when you see tomato flowers falling off
Almost all tomato plants are subjected to plant stress of some sort that can result in short periods of blossom drop. When you see tomato flowers falling off your plants, start by investigating the possible cause(s). Only then can you take action to remedy the issue. Don’t panic. Instead, think logically about what the reason might be. Explore the possible causes listed below and be honest with yourself about how you are caring for your tomato plants. Again, some of these causes are within your control and the fixes are simple.
6 reasons for tomato flowers falling off
There are a few things that could be the cause of tomato blossom drop in your garden. Most of us are familiar with other common disorders of tomatoes, such as blossom-end rot or fruit cracking that can cause tomatoes to be inedible, and just like those two disorders, blossom drop occurs for a reason. Here are six possible causes for the shedding of tomato flowers.
1. Lack of pollination
Tomato flowers are perfect, which means each blossom has both the male part (stamens and anthers) and the female part (stigma and pistil). Each flower is self-fertile, which means the flower can be fertilized with its own pollen (though cross-pollination does sometimes occur). However, the pollen doesn’t just automatically move from the anther to the stigma within a flower; it needs to be “bumped” to be released. This release of pollen can happen during a wind gust, when the plant or flower is shaken, or by the vibration action of bumble bees or other pollinators.
Pollination performed by bumble bees is known as sonication, and it is the most effective means for pollinating a tomato flower and enhancing fruit set. The bee vibrates its flight muscles as it feeds on the flower’s nectar. The resulting vibration jolts the pollen loose and fertilizes the flower.
A lack of pollinators can result in tomato flowers falling off. If a flower isn’t pollinated, it shrivels up and the plant sheds it. This is also known as an aborted flower.
If the weather is very hot, pollinators may not be active; if bee-harming pesticides are used, there may not be enough healthy bees around; or if there just aren’t enough pollinators around in general, aborted blossoms may be spotted in the garden. Plant tons of flowering plants preferred by bumble bees in and around your vegetable garden (sunflowers and coneflowers are particularly good candidates) to support as many pollinators as possible. Do not use pesticides.
If necessary, you can use an electric toothbrush or electric pollinator to pollinate your tomato flowers by hand. It’s a tedious job, but it is effective, especially in polytunnels and greenhouses where there might not be any wind or pollinators present to knock the pollen loose.
2. Large-fruited varieties
Some varieties of tomatoes produce very large fruits or produce a heavy fruit set. Plants with very heavy fruit production can trigger blossom drop (or decrease the production of future flowers). This allows the plant to shift its resources to maturing the fruit that is already on the plant.
Large-fruited heirloom tomatoes in particular are very prone to blossom drop. It’s why many of these varieties, such as ‘Dr. Wychee’s’ or ‘Cherokee Purple’, produce so few, but very large, fruits. It’s a protective mechanism of sorts because if too many large fruits are allowed to fully develop on the plant, the stems will break or the plant will not have enough resources to go around.
3. Lack of resources
And speaking of resources, tomato blossom drop can also be caused by a lack of growth resources such as light, nutrition, or water.
- Light: Tomato plants need a minimum of 8 hours of full sun per day. If the plants are too shaded, they may not be able to photosynthesize enough to support the development of a lot of fruits, resulting in some of the tomato flowers falling off the plant.
- Nutrition: If any of the macro- and/or micronutrients are lacking, the plant will only have the resources available to support a limited number of fruits. As tomatoes grow, they need a consistent supply of phosphorus, potassium, calcium, nitrogen, and other nutrients. On the flip side, too much nitrogen can result in a lot of lush green leaves with limited flowers and fruits. Use a tomato-specific fertilizer combined with a yearly addition of compost to ensure your plants have adequate nutrition in the proper balance.
- Water: The third resource to concern yourself with is water. It is also the most important one when it comes to limiting tomato flower loss. Tomato root systems spread wide, but they don’t necessarily have deep roots, which means the plant can only access water from the top 6 to 8 inches of soil. If soil moisture is not adequate or consistent, the result could be tomato flowers falling off because the plant knows it won’t have the resources available to support the resulting fruits to maturation.
Water your tomatoes deeply, targeting water directly onto the soil and allowing it to soak in. Do not let your plants dry out completely in between waterings (hello, blossom end rot!), and mulch them well. Here is a detailed article on how often to water tomatoes.
4. High temperatures can cause blossom drop in tomatoes
The fourth cause of tomato flowers falling off is the temperature. While this is something we gardeners can’t control, it is very much worth understanding why and how this happens.
Ideal daytime temperatures for pollination and fruit set are between 70 and 85°F. Thankfully, this daytime temperatures range is what naturally occurs in most climates. Temperatures over 90°F for several days in a row, however, combined with nighttime temperatures above 72°F at the same time, cause the pollen to become non-viable. When this happens, the flower shrivels and falls off. As you can see, nighttime temperatures are equally as important. It’s really when high nighttime temperature is combined with high daytime temperature that problems arise.
Even though we can’t control this, there are a few steps you can take to prevent tomato blossom drop during hot temperatures. Shading the plants during hot weather by putting shade cloth or even an umbrella over their cages when the plants are in flower may help. Including a few early-maturing cultivars and/or more heat-tolerant varieties in your garden can help offset potential challenges with high temperatures, too.
5. Low temperatures and tomato blossom drop
Extreme temperatures on the low end of the spectrum can also be troublesome for tomatoes. Since tomatoes are tropical warm-weather-loving plants, a low nighttime temperature that results in a frost or freeze will obviously result in aborted tomato flowers (and frost-blackened leaves!). But low temperatures don’t even have to dip down that far to cause issues.
Nighttime temperatures lower than 55°F translate to non-viable pollen. Since the pollen is non-viable, the flowers are not pollinated and the plant sheds the unfertilized blooms. This is one of many reasons to hold off on planting your tomatoes until the danger of frost has long passed and nighttime temperatures are safely above 55°F.
6. Stressful conditions
Stress can come in many forms. For tomato plants, humidity is a major stress factor that can result in tomato flowers falling off. Humidity levels between 40 and 70% are perfect. Beneath this ideal humidity range, pollen becomes too dry and won’t properly fertilize the flower. Above that range, it becomes too sticky for pollination. Very high humidity also results in unfertilized flowers.
Strong winds can also dry up or damage the flowers, causing them to drop.
Disease and pests can also create plant stress that results in tomato blossom drop. Disease pathogens like blight and botrytis should be managed organically (learn how to do that here). Pests – like various tomato-eating caterpillars, aphids, whiteflies, and the like – can also create stress that causes the plant to shed blooms. While a few pest insects aren’t a big deal, when numbers are high, action should be taken to control them.
When tomato flowers falling off is a sign of something else
Occasionally, spying tomato flowers on the ground has nothing to do with any of the factors mentioned above. When my son was a toddler, he was fond of plucking flowers off of my tomato plants and scattering them around the garden. Sometimes animal pests may do this as well. If tomato flowers are missing altogether and only stumps are left behind, it could be an insect pest or even an animal pest such as mice or chipmunks.
Tomato flowers falling off is often a temporary issue
In many cases, tomato blossom drop is only a temporary issue. When the day and night temperatures or humidity levels fall back into the ideal range, the plant will begin producing more flowers and fruits. When pest or disease issues are handled, more flowers will appear.
For large-fruited varieties, be sure to harvest the fruits as soon as they are ripe. If your growing season is long enough, the plant may produce more flowers and another crop of fruits.
Tomato blossom drop comes and goes for most gardeners. Like all things in the garden, you gotta roll with the punches.
For more on growing great tomatoes:
- Tomato disease management
- What to do with tomato suckers
- Micro tomatoes
- Tomato plant spacing
- Companion plants for tomatoes
- Overwintering tomatoes
Pin this article to your Vegetable Gardening board for future reference.