Why Are My Tomatoes Cracking and What Can I Do About It?

In a recent experiment we conducted to evaluate organic late blight–tolerant tomato cultivars of determinate and indeterminate types, we saw a significant number of culls, mostly due to fruit cracking. In fact, more fruit was unmarketable than marketable. In one year, 56% of fruit were classified as culls by number and 57% by weight. In the next, 53% of the fruit were classified as culls by number, and 51% by weight.

Radial and concentric cracking symptoms typically occur at the stem end of the fruit. With radial cracking, the skin splits open, forming deep cracks that extend outward from the stem scar.

With concentric cracking, fruit develop large, circular cracks around the stem end.

One reason we may be seeing more fruit cracking is that the growing season is increasingly characterized by prolonged dry spells during the early and mid-season, followed by episodes of intense rainfall toward the end, during harvest.

Tomato fruit cracking is often tied to how water moves into the fruit (Peet, 1992; Peet & Willits, 1995). As fruit grow, the flesh inside the tomato expands, and if that expansion happens quickly, the skin may not stretch enough to keep up. This stress is greatest near the stem end, where cracks are most common. As fruit ripen, the tomato skin naturally becomes weaker, making fruit more prone to cracking when internal water pressure increases (Jiang et al., 2019).

Many growers observe more cracking when soil moisture shifts rapidly from dry to wet conditions, such as after a rain event following a dry period or heavy irrigation. In these situations, a rapid increase in water availability can increase internal pressure within the fruit, raising the risk of cracking.

Cracking can also occur when water enters the fruit directly during rain events or with overhead irrigation. When fruit are ripening, small natural openings or corky tissue around the stem scar can allow water to move straight into the fruit. This direct uptake further increases internal pressure and can contribute to cracking.

Temperature also plays a role (Peet, 1992; Suzuki et al., 2007). On hot, sunny days, fruit warm up and internal pressure rises while the skin becomes less elastic, making ripe fruit more sensitive to cracking. Fruit exposed to direct sunlight are especially prone to cracking. Maintaining good leaf cover can help buffer the fruit from sharp temperature swings and keep fruit temperature more moderate, which can reduce the risk of cracking.

Management practices that can help minimize fruit cracking

Fruit cracking is a natural occurrence in tomato production, especially as the fruit ripen. The following practices build on strategies many growers already use and can help minimize cracking.

1. Water management. Aim for consistent, uniform soil moisture throughout the growing season, especially during dry spells. Drip irrigation is a good option because it delivers water consistently and helps minimize dry-wet swings. Mulches, whether organic or plastic, can also support uniform soil moisture by reducing evaporation and slowing rapid soil drying between rain or irrigation events.
2. Plant canopy/light. Healthy leaf cover helps protect fruit. Shaded fruit are less exposed to direct sunlight and tend to experience smaller temperature fluctuations. Maintaining good leaf cover, by avoiding excessive pruning and managing foliar diseases, helps moderate fruit temperature. Along these lines, if cracking has been an issue in the past, shade cloth can be an additional tool to reduce temperature fluctuations around the fruit.
3. Harvest timing. Harvest timing can influence cracking risk. If markets allow, harvesting fruit at the breaker to pink stage rather than fully vine-ripe can reduce cracking late in development. Cracking is most common as the fruit begin to change color, when internal pressure increases and skin strength decreases.
4. Cultivar selection. Plant genetics play a role in tomato fruit cracking. Cultivars differ in their susceptibility to cracking. Choosing cultivars with cracking tolerance or resistance can reduce losses. In our research, marketable yields were higher than unmarketable yields for ‘Stellar’, a determinate type, and ‘Beef Maestro’, an indeterminate type.
5. Crop load and pruning decisions. Crop load influences fruit growth rate. With a smaller crop load, water and nutrients are distributed among fewer fruit. This can increase the rate of fruit growth. Pruning, topping, or excessive suckering can shift the crop load and increase fruit exposure to direct sunlight, thereby increasing the risk of cracking. Management decisions that promote steady growth versus rapid fruit enlargement can minimize the risk of cracking. Consistent soil moisture and adequate calcium nutrition are important for this approach.

An emerging tool we are evaluating

Based on what is known about the development of fruit cracking, we are exploring a new management strategy that targets multiple cracking triggers simultaneously.

This summer, we will begin evaluating low‑cost, temporary rain‑out structures designed for field use. These structures consist of simple frames covered with either greenhouse‑grade plastic or 30% shade cloth and are intended to be deployed during periods when cracking risk is high.

The plastic coverings are expected to help limit sudden soil moisture changes caused by rainfall and reduce the amount of water that can move directly into ripening fruit during rain events. The shade cloth is intended to lower fruit temperature, reduce direct sun exposure, and soften the impact of rainfall on the fruit surface.

Rather than replacing existing practices, this approach is meant to complement current strategies by buffering fruit against sharp changes in water availability and temperature, which are closely associated with cracking. The video below shows an early prototype of the structure.

Video of a rainout shelter. Video: Tom Butzler.

References

Jiang, F., Lopez, A., Jeon, S., de Freitas, S. T., Yu, Q., Wu, Z., Labavitch, J. M., Tian, S., Powell, A. L. T., & Mitcham, E. (2019). Disassembly of the fruit cell wall by the ripening‑associated polygalacturonase and expansion influences tomato cracking. Horticulture Research, 6, Article 17. 

Peet, M. M. (1992). Fruit cracking in tomato. HortTechnology, 2(2), 216–223. 

Peet, M. M., & Willits, D. H. (1995). Role of excess water in tomato fruit cracking. HortScience, 30(1), 65–68. 

Suzuki, T., Yanase, S., Enya, T., Shimazu, T., & Tanaka, I. (2007). Effects of total integrated solar radiation on radial fruit cracking in tomato cultivation under rain shelter in cool uplands. Horticultural Research (Japan), 6(3), 405–409. 

This article benefited from editorial assistance provided by Microsoft Copilot.