Why Would a Tomato Grow Hollow Inside?

Incomplete Pollination

• The seeds inside the tomato fruit are formed individually when tomato sperm released from pollen tubes comes into contact with each of many ovules inside a flower's ovary. When too few of these ovules are fertilized successfully, due to a lack of pollinators or prolonged, pollen-killing temperatures above 90 degrees Fahrenheit during the day or below 55 degrees at night, incomplete fertilization may occur. Fruits will still form if enough of the tomato flower's ovules were pollinated to trigger the hormonal changes required, but one or more chambers of the mature fruit will have few or no seeds.

Environmental Stress

• Environmental stressors sometimes cause developing tomato seeds to fail. Low light for a prolonged period, too much nitrogen fertilizer applied before fruits are about one-third their mature size or heavy rains can cause a condition known as puffiness. The plant and walls of the fruit generally develop normally, but at least one of the chambers of each affected fruit is hollow. Puffiness is usually limited to the earliest part of the harvest and self-corrects as the season progresses; no known corrective measures exist.

Herbicide Injury

• Hormonal herbicides such as 2,4-D can cause serious reactions in tomatoes, even as a result of minor, accidental contact. Whole plant symptoms include the emergence of curled, twisted leaves or leaves that are light green or show parallel vein formation. Severe poisoning can interfere with fruit development, resulting in deformed or hollow fruits and thick, stiff, brittle or warty petioles and stems. If the tomato plant survives the herbicide contact, it will generally recover, but overall production is reduced.

Genetic Mutation

• Tomatoes and bell peppers share a similar ancestry, as well as many genes. Because of this, a tomato with a pepper-like hollowness is possible with slight variations of several genes. Heirloom types such as "Yellow Stuffer" and "Schimmeig Striped Hollow" are well-known by fanciers for their naturally hollow chambers, earning this small group of varieties with morphologically similar fruits the title "stuffer tomatoes." If you purchased your plants from an heirloom grower or started seeds yourself from open pollinated seeds, you may simply be growing a variety of tomato with hollow fruits.