Why are My Tomato Flowers Falling Off and Not Making Fruit?

Blossom Drop and Your Tomatoes

Now that your tomatoes are bursting with growth and flowers and you are anticipating the red fruit that will develop, you find flowers dropping or withering on the plant. Why is that happening? The problem is called blossom drop. The main reason is that the flowers are not getting pollinated. Tomatoes have perfect flowers, meaning both male and female reproductive organs are in the same flower. The pollen is moved from the male part (stamen) to the female part (pistil) by wind movement of the plant or by vibration of the flower by bumble bees or other pollinators. So what are the causes of lack of pollination? 

Abiotic Stresses That Lead to Blossom Drop

• Temperature – high or low temperatures can negatively effect pollination. The ideal temps for good pollination and producing fruit is between 70-85°F. If the daytime temperature rises above 85°F, or nighttime temps rise above 70°F or drop below 55°F, the pollen becomes nonviable, therefore no pollination occurs and the yellow flower dries up and falls off.
• Relative Humidity – The ideal range is between 40-70%.
• Lack of Water or Too Much Water
• Not Enough Light
• Excessive Wind – dries up the flower or physically damages the yellow flowers
• Improper Nutrition – Over fertilizing with nitrogen can also cause your plants to have lush growth at the expense of setting fruit. Under fertilizing will lead to plants that cannot supply enough energy to grow fruit. There is a fine line between over fertilizing and under fertilizing.

Biotic Stresses That Lead to Blossom Drop

• Insects
• Disease
• Heavy Fruit Set – not enough energy can be supplied to the growing flowers and producing fruit. Usually happens in the initial fruit that is set on the plants.

What Can You do to Prevent Blossom Drop?

• Best to keep your plants evenly and well-watered. Mulch around your plants to help conserve water and keep moisture levels even. This will also help prevent cracking and as long as calcium is sufficient in your soil, will reduce the incidence of blossom end rot.
• Put up some shade cloth (30% is a good option) over the plants to help cool them off a bit. This can be removed when temps drop back down to below 85-90°F.
• Best to follow the feeding label on the fertilizer and do not use ones that have high amounts of nitrogen on the label. A good balanced all-purpose fertilizer is a good choice for feeding your tomato variety in the garden bed.
• Practice crop rotation and do not put Nightshade plants (tomatoes, peppers, potatoes...) in the same bed year after year.

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