Tomatoes split due to a variety of factors which include irregular watering, high temperatures, high exposure to light, cultivar, rapid growth and humidity. Tomatoes have a tendency to split in an episodic manner and due to more than one of the stated factors. Preventing tomatoes from splitting is challenging. However, tomato cracking can be controlled by adopting certain effective farming practices.
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Types of Tomato Splits
There are a number of tomato split types. Tomatoes can crack in a ring or concentric manner, star or radial manner, or in the form of Russeting.
Concentric Tomato Splits
This is one of the most common tomato split types. Typically, cracking occurs at the top most section or shoulders of the tomato in a ring-like pattern. This type of split is also referred to as ring splitting. The cracking encircles the stem of the fruit that attaches the fruit to the vine. The splitting can be a single ring or a number of rings.
Star or Radial Tomato Splits
Star or Radial splits are also known as vertical splits. This is the most severe splitting of the tomato fruit. It often exposes the flesh of the tomato. The cracking occurs along the side of the fruit in a longitudinal fashion starting at the stem. In cherry tomatoes, the splitting can be so severe as to run all the way from the top to the bottom of the tomato. Radial splitting is sometimes referred to as bursting. This speaks to the ungracious manner it sometimes occurs.
Russeting
Tomato Russeting is yet another form of splitting found in tomatoes. Russeting marks are shorter, smaller and appear superficial. Russeting may take a concentric pattern.
Minute Cracks
Tomato fruit is also prone to minute cracks. These are fine microscopic cracks on the skin of the tomato which are not necessarily visible to the naked eye. These minute splits give way to more visible cracks that become apparent after the fact.
Multiple Tomato Splits
Finally, a tomato fruit can suffer multiple types of splits in severe cases. These may be a combination of some of the split types discussed above. In such cases, tomato splitting obviously becomes apparently devastating to the fruit.
Why Do Tomatoes Split
Why tomatoes split has been a matter of intense study going as far back as the 1930s. It is a complex and continuing area of research which remains desirous for more understanding. Extensive research over the many decades has definitively established some causes of cracking in tomatoes. However, due to the difficulty of studying the phenomena, there are also theories that have been put forward mostly derived from laboratory studies.
The following are some causes of splitting in tomatoes.
Change from dry to wet soil conditions causes tomatoes to split
A switch from dry soil conditions to wet soil conditions is one of the main causes of splitting in tomatoes. This is down to the tensile strength of the tomato skin itself. Tensile strength refers to the resistance of a material to tearing or breaking under tension.
High moisture levels cause the skin of the tomato fruit to have low tensile strength. When the tomato plant is watered from a position of dry soil conditions, the fruit enlarges rapidly creating minute splits which develop into apparent cracks.
Skin strength increases when moisture levels are lower. On the other hand tomato skin strength decreases when moisture levels are higher.
To better control splitting in tomatoes, the tomato tree is watered regularly and evenly. This avoids extreme swings in tensile strength due to sudden moisture changes.
To better control splitting in tomatoes, the tomato tree is watered regularly and evenly. This avoids extreme swings in tensile strength due to sudden moisture changes.
Furthermore, overhead watering of tomatoes is discouraged. Minute cracks on the tomato skin absorb water into the fruit causing swelling and bursting. This is presumably one of the reasons some tomato varieties burst uncontrollably following a rain storm.
High temperatures and exposure to sunlight causes tomatoes to split
Tomatoes require at least 6 hours per day to optimally thrive. However, this exposure to sunlight is a double edged sword. Mid afternoon sun is particularly responsible for heightened temperatures.
Researchers have established that high temperatures in general and sudden temperatures in particular, induce splitting in tomatoes. High temperatures are thought to exert pressure on the flesh of the tomato whilst at the same time softening the skin of the fruit and reducing its tensile strength. This cocktail of developments leads to raptures.
Rapid fruit growth causes tomato splits
Apparently, rapid tomato fruit growth rate predisposes the tomato to cracking. Genetically, tomato fruit has no effective mechanism to prevent fruit growth save through the regulation of water pressure.
Different factors induce rapid tomato fruit growth which makes the tomato susceptible to cracking. The standard practice of pruning indeterminate tomatoes of side shoots predisposes them to cracking. The increased energy and food that is redirected to fruit production through pruning increases growth rate and size of the tomato fruit. This increases the risk of splitting.
Furthermore, topping the tomato plant and widening spacing between plants has been suggested by researchers to increase risk of splitting in tomato fruit. This is not all. The removal of some fruit from clusters leaving others attached increases susceptibility to cracking of the remaining fewer fruit due to increased food supply and energy which is not present when competition is higher.
This also explains incidences of increased cracking in tomatoes towards the end of the season when a lesser number of fruits remain on the vine.
In cases where rapid fruit growth does not result in outright cracking, Russeting and minute splits may occur.
Jump to our in-depth feature on Indeterminate Tomatoes
Tomato fruit anatomy causes splitting
There is a correlation between the anatomy of tomato fruit and its susceptibility to splitting. Researchers have identified the necessary tomato skin characteristics that offer resistance to cracking. High skin tensile strength and high elasticity when the fruit starts ripening are important factors. Tomatoes that have weak skin when the fruit starts turning to pink before ripening are prone to splitting.
Furthermore, certain fruit shapes and sizes predisposes tomatoes to splitting. As a general rule of thumb, the bigger the size of a tomato the greater its susceptibility to cracking. As a fruit continues to grow in size, the physical pressure on the outer membrane or skin increases. Whichever section of the fruit with greatest stress will split. Tomato fruit bears the most pressure at the calyx. This is where ring splitting also occurs, for example.
Cultivar and genetic differences causes tomato splitting
Certain tomato varieties split more than others as a result of genetic differences. Sweet tomatoes provide a good example of this. The Sungold tomato is a very sweet cherry tomato. This cultivar is notorious for cracking especially following some rains.
The reason this happens with sweet tomatoes is that areas of high sugar concentration attract water flow to themselves. Due to the sweetness, Sungold cherry tomato fruit has a tendency to pull water from the plant stems and leaves to the fruit. This exerts pressure on the skin of the tomato leading to splitting. Sungold tomatoes are often described as bursting when they crack. This can happen at scale in a field.
In the case of Sungold cherry tomatoes, efforts to develop a better tomato variety that is resistant to cracking have not yet been successful. One of the reasons is the yet to be fully understood genetics of crack resistance.
High temperature differentials cause tomatoes to split
Researchers have developed a theory which suggests that night and day temperature changes are responsible for cracks in tomatoes. While day time may have been characterised by high temperatures, night time temperatures are thought to contract tomato fruit. It is thought the negative pressure created due to this drop sucks in condensed moisture or that is already present on the skin of the tomato.
As day time returns and temperatures rise, positive pressure builds up in the tomato stretching the outer membrane which is the skin. Since the skin of the tomato is 97% gas-impermeable, the trapped gases expands the fruit in volume leading to cracking. Researchers presume that the higher the day and night temperature differential, the greater the stress on the skin of the fruit.
Excessive watering causes tomato cracking
Excessive watering of tomatoes is a well known and common cause of splitting in tomatoes. The only way for an excessively watered tomato fruit to manage water supplied to it is to expand or cause movement of the water back into the plant. Under already highly humid conditions this is unlikely. The tomato responds by expanding leading to immediate cracking or minute cracking which becomes visible at a later stage.
How to Prevent Tomatoes from Splitting
Preventing cracking in tomatoes is challenging. Full proof prevention is currently not achievable. As already demonstrated, some of the best practices when farming tomatoes such as pruning, are in of themselves causes of tomato splitting. Furthermore, biotech interventions are currently limited by the fact that genes that cause radial splitting, concentric splitting and Russeting in tomatoes are different.
Nevertheless, the following are some practical ways to prevent and minimize splitting of tomatoes.
Avoid overwatering
Avoiding overwatering tomato plants is an effective way of controlling splitting. Since this is the most common cause especially among home gardeners, results are immediate.
Water Tomatoes Evenly
Watering tomatoes evenly and regularly avoids soil dryness which has been implicated in causing cracks in fruit once the tomato is watered. Regular and even watering is achieved by developing a consistent watering program.
Harvest Tomatoes Early
Harvesting tomatoes early is an effective way of avoiding cracking caused by thick skin. Tomatoes can be harvested green or once they start turning pink. Green tomatoes have a thicker skin than those fully ripened. They can be left to ripen while in storage. However, the downside is that tomatoes that ripen on the vine tend to be more flavourful than those removed early.
Close Row Spacing
Researchers have identified close row spacing as effective in reducing cracking. Close raw spacing reduces fruit size due to food and energy competition and also decreases fruit temperatures. These factors have already been discussed as influencing splitting in tomatoes.
Harvest Tomatoes Before the Rains
At the first sign of rain, tomatoes can be harvested from the garden. This is particularly the case with some cherry tomatoes. Harvesting tomatoes before the rains is only practical when working with small home gardens. It may not be a viable response at scale.
Grow Resistant Varieties
Deliberately growing cracking resistant varieties is an effective method of better controlling splitting in tomatoes. These varieties have elastic skin that responds better to fruit growth and expansion. Crack-resistant tomatoes include Early Girl, Jet Star and Juliet among others.
Maintain Good Calcium Nutrition
Calcium (Ca) helps increase the tensile strength of tomato skin. Ca appears to strengthen cell walls. This reduces cracking in tomatoes and many other types of fruits. Ca is also effective in protecting the tomato fruit against blossom end rot itself, a sign of Ca deficiency.
Utilize Mulching
Grass, leaves or plastic mulching is useful in preventing soil moisture loss which leaves the soil borne dry. Although not directly responsible for reducing splitting, retention of moisture prevents the creation of the right conditions that subsequently lead to tomatoes splitting.
Effect of Splitting on Tomatoes
When tomatoes split the immediate effect is poor aesthetics. The tomatoes cease to look appealing and may not be usable at all. When grown on a commercial scale, split tomatoes diminish in market value and may turn out to be a total commercial loss.
Apart from these effects, cracked tomatoes are heavily susceptible to other serious problems. They easily attract fruit flies, worms, birds and other pests. The pests may extend their visitation to include otherwise healthy plants and fruit. Cracked tomatoes tend to easily rot, develop fungus, mold and bacteria thus growing the problem.
What to do with Split Tomatoes
What to do with cracked tomatoes will depend on the severity of the split and subsequent developments. If the tomatoes are still intact and unaffected by disease, fungi or pests they may still be edible. This is usually the case if they are picked immediately after the splitting. Such tomatoes can be used in recipes such as salads, tomato sauces and even cooking.
To avoid health problems, split tomatoes must be disposed of if they show signs of going bad or being consumed by pests.
Why Do Tomatoes Split (Video)
This video provides a concise overview of why tomatoes split.
Conclusion
There are a variety of reasons why tomatoes split. Irregular watering, high temperatures, high exposure to light, cultivar, rapid growth and humidity are all potential causes of cracking in tomatoes. These factors can happen in combination or singularly. Even as tomatoes split, there are different types of splits, some subtle and some invisible, which all impose varying degrees of damage to the tomato fruit. Although tomato splitting is virtually impossible to completely eliminate, there are many practical things that increase the growers control over splitting tomatoes. Overall, research seeking better understanding of the genetic mechanisms behind tomato splitting is ongoing.
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