Blossom Drop

Tomato Blossom drop

Blossom drop is a problem that can affect several plants in the vegetable garden.  Peppers, snap beans, and a few others can be affected by blossom drop, but, by far, the largest number of questions I get is about tomatoes.

Blossom drop is characterized by the sudden drop from the vine of the blossoms. In the case of tomatoes, the small yellow flowers that usually precede fruit set wither in the vine and drop off.  Tomatoes are self-fertile, and self fertilize.  However, the pollen doesn’t move by itself from the stigma.  There needs to be some action to enable this.  This is a huge problem in greenhouses where still air and a lack of pollinators exist. 

Give it a Shake

We typically “shake” our tomato plants gently to encourage the pollen to fall from the stigma into the flower.  In large commercial greenhouses, I have seen videos of workers using electric toothbrushes to vibrate the flowers. 

A lack of pollination can cause blossom drop.  As the flower matures, if it isn’t pollinated, it withers and drops from the vine.  This can be a problem in greenhouses and where plants are grown tightly together.

Are Your Plants Stressed Out?

blossom drop tomato blossoms

The other causes of blossom drop are stress-related.  One of the chief causes of problems with tomatoes is temperature issues.  Extremes in temperature can cause the plant to shed blossoms as it attempts to cope with temperature extremes.  Temperatures above 85 degrees F or nighttime temperatures below 55 degrees F can cause blossom drop.  This is due to the change in the pollen when the temperature extremes exist, which prevents the pollination of the blossom.

Humidity and Stress

Humidity can also cause the same sorts of problems.  Ideally, tomatoes prefer a humidity range between 40 and 70 percent.  If the humidity remains to hight or low for extended periods, pollination will not occur, and the blossom will abort. 

Overfertilization or feeding can cause tomatoes to drop blossoms.  Overfeeding your plants results in high nitrogen concentrations, which encourages the plant to produce vegetation and inhibit blossom production and pollination.  The result will be a blossom drop and poor fruit set.  Too little nitrogen results in thin spindly vines that cannot support the plant.

Keep the Water Flowing

Tomatoes, when blooming and producing fruit, are prodigious users of water.  A lack of water puts the plant under stress and causes blossom drop.  All too often, the cause of this is quick, shallow watering, which does not provide the tomatoes proper moisture.  Poor soil can also contribute to this by preventing proper infiltration of the water into the root zone.  The solution is to water slowly, giving the water time to infiltrate deeply into the soil.  Maintaining good soil health is vital.  Mulching can also help retain moisture in the soil.

The Bug in the Ointment

Insects or diseases can also put the tomato plant into a stressful situation that will cause blossom drop.  Check for pests and diseases when your plant begins to drop blossoms.

Being too Productive

At times, a healthy tomato plant will set so many blossoms that it cannot possibly support fruit production.  To protect itself, it will drop blossoms as a way to manage the fruit load and the stress on the support systems of the plant.  This is a natural process and to be expected.  Other plants do the same.  I have noticed our cucumber vines in our greenhouse dropping blossoms due to the overabundance of flowers.  We have still had an amazing harvest of pickling cucumbers despite the masses of blossoms that ended up on the greenhouse floor.

Tomato Tips

Blossom drop greenhouse tomatos

To have the best chance for a good tomato harvest, follow a few simple steps.

  • Plant varieties that are suited to your growing zone and conditions.
  • Help with pollination by shaking or vibrating your tomato vines
  • Feed properly.  Use organic fertilizers like compost or compost tea.  It is almost impossible to overfertilize with organic fertilizers
  • Water properly.  Water should be applied slowly and evenly and allowed to soak deep into the root zone.  Add mulch around your plants to help maintain moisture levels in the soil.
  • Control insects and diseases.  Remember that healthy plants are less susceptible to pests and diseases.  Keep your plants healthy by maintaining healthy soil with a rich soil biome.

For more information about growing tomatoes, plant stress, and good organic practices, visit our web site at West Texas Organic Gardening.

For more specific answers to your questions, these articles may help.

Fertile Soil

Feed the Soil

The Organic System – Soil

Raising Tomatoes in West Texas

If you have more questions, contact us through our website or post your questions to our Facebook page @westtexasorganicgardening