What Causes Tomato Blossoms To Drop?

The stems of your gorgeous tomato plants just turned yellow and dropped all their blooms, and you’re suddenly wondering why. This phenomenon is known as “blossom drop.”

There are several possible causes, and by careful observation, you can figure out what happened and take steps to prevent the problem from arising again.

Ripe tomatoes ready for pickingPin

Read on to learn more about the main reasons for blossom drop on your tomato plants listed below.

8 Main Reasons For Tomato Blossom Drop

1. Temperature

Tomato plants thrive at specific daytime temperatures, between 70° and 85° degrees F during the day and no lower than 55° degrees F for nighttime temperatures. 

While tomato plants can stand for a short period of time outside of this ideal range, it will cause plant stress if the temperature remains too hot or too cold. Stressed tomato plants will not set blossoms and will start to drop any flowers that are formed.



Moreover, it is well known that extreme temperatures can adversely affect flowering, pollination, and fruit set of tomatoes. Temperature fluctuations will also hinder tomato developmental stages.

Related: Tomato Do’s and Don’ts – Which Ones Do You do?

Solutions:

If you live in a colder zone, wait until the night temperature is consistently above 55 degrees Fahrenheit before transplanting your tomatoes into your garden bed.

You may also need to provide cover for the plants during cold snaps. In addition, it’s also important to cover at night using clear plastic or a tarp when frost or cold nights are in the forecast.

If you live in a warmer zone, look for spots in your garden that might be cooler during the day. A tree that provides partial shade during the afternoon heat might be ideal.

Alternative choices include the east wall of a building that receives morning sun and daytime shade or a garden cover that shades the plants. You might also wait until later in the season, when temperatures have cooled, before the plant blooms.

In both cases, seek out tomato varieties adapted to your zone. A variety that produces well in northern zones may not serve well in warmer climates, and vice versa.

2. Lack Of Pollination

Tomatoes are self-fertile, so they don’t require the pollen of a different tomato plant. The pollen from the stamens (male) will transfer to the sticky stigma or the tip of the pistil (female) under proper conditions.

However, several factors can affect pollination. When there’s no provided pollination aid, the sterile pollen will not move well by itself from the anther to the stigma because of poor pollination. And if blossoms aren’t pollinated, they will drop off.

In addition, pollen that is too wet or in conditions with highly humid weather leads to the pollen forming sticky clumps. Conditions that are too dry will also affect pollination. 

The ideal humidity range is between 40% and 70%. Excessive heat will also kill pollen. Insect pollinators help move pollen, and a lack of beneficial insects reduces pollination.

Solutions:

You cannot really do anything about problems of excess humidity or rain. In extremely dry areas, one can raise the humidity around the tomato plant by gently misting the plant in the morning. 

Proper humidity levels range between 65% and 85% percent for the optimal development of the tomato plant.

You can also attract beneficial insects like bees and butterflies by companion planting lots of flowers near the tomatoes. Some herbs, like dill or sage, might be a choice, as well as flowers that produce lots of nectar or pollen.

Moreover, many factors may inhibit the proper pollination process, including the low insect population or lack of air movement. In these situations, attempting hand-pollinating tomatoes is a good way to ensure your tomato plants bear fruit. 

Hand-pollinate the tomato blossoms by gently taking a small paint brush, dabbing it over the flowers, capturing the pollen from the anthers, and rubbing it on the stamens. 

If you choose to adopt this method, be sure to use only the pollen of each particular plant without attempting to cross-pollinate them.

What Is A Tomato Blossom Drop Spray?

Many gardeners use a tomato blossom drop spray containing kinetin a cytokinin hormone, to prevent the premature dropping of flowers from tomato plants.

The spray works to help regulate the balance between growth and abscission (the natural process of dropping flowers or fruit). The spray makes the plant “pause” and focus on flowering.

This “pause” can overcome environmental causes and physiological factors that often lead to blossom or fruit drop. More flowers, more fruit, resulting in an increased yield.

Blossom drop or blossom set spray is used on tomatoes, peppers, okra, and squash.

3. Nutrient Deficiencies Or Excesses

Like all plants, tomatoes need proper nutrients for plant growth, like nitrogen and phosphorus. A lack of nitrogen or phosphorus will lead to spindly small plants. In either case, the plant won’t produce many blooms with nutrient imbalance, if it blooms at all, to begin with.

Since the plant is weak, it may be susceptible to environmental stress, and its blooms will fall off at the first sign of any other problem. 

In contrast, excessive nitrogen encourages the plant to produce tremendous green growth without necessarily blooming. Likewise, excess nitrogen may also cause flowers on tomato plants to fall off and hinder the growth of tomato fruit.

Calcium is often cited as a key nutrient for tomatoes, with ground-up eggshells being the ideal answer. Most soils aren’t deficient in calcium, and even if they are, eggshells won’t decompose in the garden soil in any useful timespan.

Solutions:

Review your cultural practices. Tomatoes need balanced nutrients, such as nitrogen and phosphorus, to grow successfully. Other essential nutrients include potassium, potash, calcium, magnesium, and other trace minerals.

Related: 7 Natural Homemade Tomato Fertilizer Options

If your plant looks normal and not spindly, nitrogen and phosphorus probably aren’t an issue. The solution is to provide a good dose of a balanced fertilizer for tomatoes twice.

The first dose should come when you transplant your tomato plants into garden beds. The second dose of tomato fertilizer should come when the plants start to set blossoms. More fertilizing than this probably isn’t necessary.

4. Harmful Insects

Tomato plants are prone to many common garden insect pests and diseases. Aphids and other insects are a problem, as are slugs and snails. These insect damages can stress the plant and cause tomato flowers to fall off.

Related: How To Control White Flies on Tomato Plants

Solutions:

Constant vigilance and prevention are your best tools in dealing with pests and diseases. Keep an eye out for aphids. These can be washed away with a good dousing of the plant itself, or you can try to introduce beneficial insects like ladybugs that eat aphids. 

5. Fungal Diseases and Viruses

Tomato fungus diseases may also cause blossom drops in your plants. An example is the Tomato yellow leaf curl virus, an extreme disease commonly transmitted by whiteflies.

For as long as 2 to 3 weeks, tomato plants may have symptoms yet after infection. However, indications may soon surface after that. These include yellow leaves (chlorotic), upward curling of leaves, blossom drop, and stunted growth.

Solutions:

Ensure you’re looking for the first signs of diseases or rot. Then, be sure to clip off and discard any leaves with disease or rot. Don’t put the diseased leaves in your compost heap; eliminate them entirely.

Removing infected plants will also help slow the spread of the disease. They should also be immediately bagged to prevent the spread of the whiteflies further. 

If you decide to use pesticides or fungicides, always use them by following the label directions to stop the further growth of diseases.

6. Over-watering And Under-watering

Tomato plants require a lot of water. However, too much water cause root rot that will stress the plant and cause blossoms to drop off. Their leaves will also turn yellow, develop cracks on their fruits, and develop blossom-end rot

In addition, excess water can drive the air out of the soil around the plant’s roots, drowning the healthy roots and killing off the entire plant. 

Lack of water is just as bad as too much, especially when grown in places with hot weather. Without enough water, plants will struggle to survive and not produce many blossoms. 

Underwatering or shallow watering will cause tomato flowers to drop, as it needs even sufficient water for tomato fruit production.

Solutions:

The best solution to combat water stress is to start with a deep watering system that allows you to deliver an appropriate amount to the deep roots of tomato plants daily. Whatever system you elect to use, water the soil around the plant and not the plant itself.

Watering your tomato plants with around 1″ to 2″ inches of water weekly is preferred. Moreover, the best time to water the plant is in the morning, before the day’s heat has come up, so that any water that does get on the plant does not burn the leaves.

7. Too Many Blooms to Begin With

The tomato may set too many blooms at its first flowering. This sounds like a good problem, but the tomato will drop its excess if it cannot produce all the fresh tomatoes available. The situation may seem catastrophic as it leads to a lack of nutrients.

Solution:

Be patient. The problem will usually take care of itself with the second and subsequent flowerings of the plant.

JOIN Our FREE Plant Care Newsletter 

By entering your email address you agree to receive a daily email newsletter from Plant Care Today. We'll respect your privacy and unsubscribe at any time.